Comparing Photogrammetry and Remote Sensing

Comparing Photogrammetry and Remote Sensing

If you work in civil engineering, construction, archaeology or any field where understanding physical layouts is critical, you can likely use data and mapping to greatly benefit your work. Two techniques in particular, photogrammetry and remote sensing, provide a wealth of valuable data to increase precision and accuracy in planning, analysis, construction and excavation.

What Is Remote Sensing?

Remote sensing involves identifying and measuring objects or events — for instance, weather events — without contacting them directly.

Remote sensing relies on detecting different wavelengths of light radiation. Objects may emit or reflect this radiation, and remote sensing can identify and process even small differences across an extensive array of wavelengths and spatial orientations. Professionals use these differences to identify objects and categorize them according to their type, material or location. They can also use them to measure slopes and distances.

What is remote sensing used for? Satellites have used remote sensing in meteorological operations for decades. Remote sensing first came into use because of the high number of color bands in satellite imagery. The technique used those color bands to collect 2D information for weather tracking and geographic information system (GIS) mapping, for instance. Today, many satellites in orbit still use remote sensing to gather a range of information from the Earth to evaluate weather and land cover and generate maps.

Remote sensing doesn’t have to work at such great distances, however. This method is also useful for gathering data for terrestrial projects, like surveying or earthworks construction. Remote sensing encompasses any observation and measurement methods that do not rely on direct contact with the object or landform in question.

What Is Photogrammetry?

Photogrammetry uses imaging rather than collecting light wavelength data. It involves determining the spatial properties and dimensions of objects captured in photographic pictures.

Albrecht Meydenbauer, a Prussian architect who made some of the first elevation drawings and topographic maps, first used the term in 1867. Today, an airplane, satellite, drone or even a close-range camera might record digital images for photogrammetric use.

Photogrammetry relies on a technique known as aerial triangulation to measure changes in position. This method involves taking aerial photographs from more than one location and using measurements from both places to pinpoint locations and distances more accurately. The various photographs provide different lines of sight or rays from the camera to specific points. The trigonometric intersection of these lines of sight can then produce accurate 3D coordinates for those points.

Modern photogrammetry also sometimes relies on laser scanning as a complement to traditional images. Light detection and ranging (LIDAR), for instance, which uses pulsed lasers to measure distances, often assists in photogrammetry performed from aircraft and satellites, as well as on the ground.

Photogrammetry breaks down into two main branches: metric and interpretive. Here’s more information on them:

  • Metric photogrammetry: This branch of the field involves taking exact measurements and frequently finds use in technical industries like engineering and surveying. Metric photogrammetry uses a metric camera to make precise computations and evaluate exact sizes, shapes and positions of objects or topographical features. It is also useful for determining coordinates and relative positions.
  • Interpretive photogrammetry: This branch of the field involves identifying general image features like sizes, shapes and patterns. It is useful for adding ancillary information to photographs rather than making direct calculations.

What is photogrammetry used for? Photogrammetry is exceptionally common in applications such as measuring landforms and terrain and developing topographic maps. Many industries, including fields as diverse as architecture, construction, engineering, forensics, forestry, geoscience, law and medicine, rely on the precise and accurate 3D data photogrammetry provides.

Comparison of Photogrammetry and Remote Sensing

What are the main differences to consider regarding photogrammetry vs. remote sensing? Explore them below:

  • Data type: One of the main differences between photogrammetry and remote sensing lies in the kind of information collected. Remote sensing collects data in the form of light and color. By detecting different wavelengths of light radiation, it can generate maps. Instead of measuring wavelengths of radiation, on the other hand, photogrammetry uses imagery to measure coordinates in space.
  • Number of dimensions: These differences also mean remote sensing tends to work in two dimensions while photogrammetry tends to work in three dimensions. Remote sensing can create informative 2D maps, while photogrammetry is ideal for more complex 3D modeling.

Who Uses These Processes?

Below are a few applications that frequently use remote sensing and photogrammetry:

1. Emergency Management

In an emergency, professionals need reliable data to develop plans for stanching floodwaters or containing fires. Remote sensing can provide an accurate picture of topography and map the scale of the disaster. Photogrammetry enables teams to generate reliable 3D models for planning evacuation routes or containment approaches.

2. Environmental Impact Assessment

Environmental science often uses remote sensing to gain concrete data about how ecological changes have progressed. For instance, a team might use remote sensing to map the decrease in foliage in a particular area or track the recession of glaciers or the polar ice caps.

3. Earthworks Development

Building earthworks requires detailed information about the landscape and topography. Engineers use remote sensing and photogrammetry to collect necessary data for grading the land and constructing features like roads, bridges, dams, canals, utility layouts and distribution and drainage systems. A drone can fly over a job site, for example, to capture data and turn it into a point cloud for use in planning projects.

4. Mining Monitoring and Expansion

Mining companies need reliable methods for monitoring their existing mines and scouting for new sites. Remote sensing and photogrammetry enable companies to generate maps and 3D images for these purposes.

5. Archaeological Recreation

Archaeological teams often need detailed 3D models so they can examine sites without disturbing delicate artifacts. Taking thousands of still photos and compiling them through photogrammetry enables these teams to develop highly accurate and realistic 3D models. Photogrammetry is also often indispensable for the virtual reconstruction of cultural heritage sites.

6. Forensics Analysis

At a crime scene, it’s essential to disturb the evidence as little as possible. But law enforcement personnel still need ways to examine the scene. Photogrammetry offers an ideal solution — a drone can fly overhead to take photographs and develop reliable 3D models for use in the investigation, as well as for lawyers and insurance adjusters. In countries like Colombia and Guatemala, photogrammetry has also helped detect and document clandestine graves where commercial satellite imagery was insufficient.

7. Architectural Recording

When architects or restoration specialists must survey historical buildings, remote measurement helps them ensure the structures’ continued integrity. Photogrammetry allows these teams to develop 3D maps, typically generating elevation drawings at scales of 1:20, 1:50 and 1:100, without touching or damaging the architectural features.

Work With the Experts at Take-Off Professionals for Photogrammetry Services

To see the benefits of reliable 3D imaging in your next construction project, partner with TOPS.

Why should you work with experts for photogrammetry services? When you do, you’ll gain the peace of mind that comes from working with professionals who have years of experience in the industry. Photogrammetry is a complex process, so collaborating with seasoned pros minimizes errors and increases the chances of a successful project.

Working with the experts at Take-off Professionals also means partnering with teams that specialize only in data. We don’t provide software or hardware — instead, we focus all our attention on data and modeling. You’ll get the careful attention your project deserves while knowing we have the in-depth focus to tackle even the toughest challenges. We also have dedicated engineering and surveying teams who can provide tailored guidance for civil engineering.

Contact us today to learn more about how photogrammetry can enhance your work.

Depth Map Sequences vs. Point Clouds

Depth Map Sequences vs. Point Clouds

A 3D model lets a civil contractor or construction professional perform machine control and layout planning before and during construction. Depth map sequencing and point cloud modeling are two examples of 3D modeling often used in construction. Although the two methods have some things in common, they ultimately have different goals and purposes. A point cloud is usually a collection of data points that form a shape, while a depth map conveys information about the distance between two objects in space.

Learn more about the differences and similarities between point cloud modeling and depth map sequencing below.

What Is Point Cloud Modeling?

Point cloud modeling produces a set of small data points, which exist in three dimensions and on X, Y and Z coordinates. The data points represent a part of a surface in a defined area, such as the area of a construction site. When arranged together, the points produce a clearly identifiable structure.

The more data points in the point cloud, the more detailed the structure and image will be. You can compare the data points that make a point cloud to the pixels that make up a digital image. The more pixels there are in an image, the clearer the picture is.

Point Cloud Modeling Methods

Point Cloud Modeling Methods

Two methods can produce point cloud models — photogrammetry and Light Detection and Ranging (LiDAR), also known as remote sensing.

Photogrammetry is a relatively old process of collecting information about objects and surfaces. When photogrammetry is part of point cloud modeling, a drone takes multiple images of a work or construction site at various angles. After the drone takes the photos, the images are collected together and processed. Processing the images stitches them together, creating an overlapping picture and allowing you to build a 3D model from them.

While photogrammetry uses images to help you produce a 3D model, LiDAR uses laser beams. Typically, a device that transmits a laser is attached to an aerial vehicle. The vehicle goes up into the air, directing laser beams back to the Earth. The laser beams bounce off the Earth’s surface, returning to the vehicle.

LiDAR measures how long it takes for the laser beams to travel from the surface back to the aerial vehicle. In some ways, it is similar to echolocation, except instead of using sound waves to measure distances, LiDAR uses light beams. The information collected by LiDAR can then be transformed into a 3D model. Once the images or information is collected, the process of transforming them into a 3D model is similar for both photogrammetry and LiDAR.

Often, LiDAR collects more useful information than photogrammetry, particularly if there is dense tree cover over the area being measured and modeled. A photo can’t push through branches and leaves to give an accurate measurement to the ground below. A light beam can travel through the spaces or openings in the tree cover, allowing you to see how far below the ground is.

One drawback of LiDAR is that it can be more sensitive to weather conditions than photogrammetry. It can also have difficulty collecting accurate information when the surface is reflective.

The two methods also vary drastically regarding price. If you are on a budget, one method of capturing information for point cloud modeling might be more appropriate for you than the other.

What Is Point Cloud Modeling Used For?

Point cloud modeling has several uses in construction and engineering projects. You might need to create a point cloud for the following:

  • Surveying: Point cloud modeling can quickly and cost-effectively produce representations of roads, bridges and other complex structures.
  • Earthworks projects: Earthworks projects, such as excavating to produce a new road or lay pipe, can also benefit from the use of drones or aerial vehicles and point cloud modeling. Point cloud modeling allows your company to keep tabs on a project without visiting the site in person. It can also help improve worker safety on-site.
  • 3D models: Point cloud modeling also allows for the construction of more accurate 3D models for a project. The data captured during point cloud modeling allows you to accurately identify and distinguish objects in the area so you can create a precise representation.

Benefits of Point Clouds

If you need to create a 3D model for an engineering or construction project, using point cloud modeling offers multiple benefits:

  • Accuracy: A point cloud model is an accurate representation of an object or area. Both photogrammetry and LiDAR allow you to capture enough information to produce a detailed, correct model of a particular area.
  • Ease of budgeting: Since the process of capturing information for point cloud modeling is so accurate, you can develop a budget for your project without too much concern about going over or spending more than you can afford. Point cloud modeling also minimizes the risk of mistakes, meaning you will spend less time and money on correcting errors. You will also save time on your project, which translates to cost savings.
  • Efficiency: Point cloud modeling is a much more efficient process of building a 3D model, especially when compared to the time and effort it would take to create 3D models by hand. Increased efficiency means your project gets off the ground and can be completed sooner rather than later.

What Are Depth Map Sequences?

A point cloud lets you see every data point used to create an image. A depth map gives you a view of the data points from a particular angle. Another way to look at a depth map is as a 2D image that has been manipulated to look like a 3D image. A depth map has information on the distance between objects in a picture. It’s often shown in grayscale.

After the creation of a depth map sequence, the grayscale image is usually merged with the initial photo. Combining the two creates a third picture that looks 3D.

How to Create a Depth Map Sequence

To create a depth map, you start with a 2D image. Since the goal is to turn a 2D image into a 3D one, the source image must have several layers. Ideally, the starting photo will have a background, middle ground and foreground. To produce the depth map, you’ll need a photo and an image-editing program, such as Photoshop.

Start by selecting areas of the foreground, using the magic wand or another selection tool to trace them. After tracing each section, create a layer. Once you’ve selected and created the layers for the foreground, select the part of the image that makes up the middle ground. After that, select the section of the photo that will be the background.

After selecting and creating the layers for your 3D image, grayscale each layer. The layers in the background should be a darker gray than the foreground layers, which should be the lightest gray. You might find it easier to work if you grayscale the image before you begin cutting out the layers.

Once you’ve produced the grayscale image, you’ll merge it with the original picture in the photo editing tool. The overlap of the two images produces a photo that looks 3D.

What Are Depth Maps Used For?

One use of a depth map sequence is to create 3D advertising images. Another use is for producing 3D models for engineering and construction projects. Compared to a flat image, a depth map lets you see what is around or behind objects in a picture, providing you with a more accurate presentation of the area.

Point Cloud Modeling vs. Depth Map Sequences: Similarities and Differences

The primary feature that point cloud modeling and depth map sequences share is both use images to transform data into 3D models. The two methods give you a way to view information.

One of the differences between depth maps and point cloud modeling is the image’s viewpoint. A point cloud lets you see every point. A depth map only gives you a view of the points visible from a particular angle.

Another way to look at the differences between a depth map and a point cloud is to consider the image’s dimensions. Cartesian coordinates include an X-axis and Y-axis, which intersect each other perpendicularly. X and Y axes are all that is needed for 2D images.

When an image is 3D, there’s also a Z-axis, which intersects the X and Y axes and runs vertically. X and Y are horizontal. With a point cloud, you can see the image from all three axes. In contrast, a depth map only gives you the information found on the Z-axis.

Work With a Data Modeling Expert

Work With a Data Modeling Expert

Your project’s success depends on what you do with your data. The team of experienced engineers at Take-off Professionals (TOPS) can transform your data into a working 3D model. All you need to do is send us your plans and the CAD files and we’ll take care of the rest. To learn more about our services and the benefits of working with data modeling experts, get in touch with us today.

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The Evolution of Modeling in Construction

The Evolution of Modeling in Construction

The Evolution of Modeling in Construction

Building information modeling (BIM) has established itself as a useful process for architects and construction teams over the past two decades, as it allows users to create intelligent 3D models that include every detail of a building. This process also enables you to document management, coordination and simulation throughout your project’s life cycle, which includes planning, designing, construction, operation and maintenance.

Below, you’ll learn more about the evolution of BIM, one of the most important chapters in the history of construction. This story is a complex narrative that involved the U.S., Western Europe and a set of Soviet countries competing with each other to develop a flawless architectural solution to replace 2D workflows.

History of Modeling in Construction

BIM was a concept long before the technology was advanced enough to make it a reality. Notable early events in the history of modeling include the following.

Engelbart’s Vision

The conceptual foundations of BIM technology date back to the 1960s, when computing was still in its infancy.

In the paper Augmenting Human Intellect, engineer and inventor Douglas C. Engelbart provided his vision of the future. He stated that architects could begin designing a structure just by entering a series of data and specifications — for example, a 5-inch slab floor, 8-inch concrete wall and so on. As they began designing the structure, they could look at the model and adjust the parameters.

Solid Modeling Programs

In the 1970s and 1980s, solid modeling programs emerged. The two primary methods these programs used to display and record shape information were:

  • Constructive solid geometry (CSG): CSG uses numerous simple shapes that can either be solids or voids. The shapes can combine and intersect, subtract or combine, resulting in what appears to be more complex forms.
  • Boundary representation (BREP): Boundary representation, defines objects using their spatial boundaries by detailing the edges, points and surfaces of a volume.

Charles Eastman and the Building Description System

In the 1970s, architect and computer scientist Charles Eastman designed a project called the Building Description System (BDS). This program featured a graphical user interface, perspective and orthographic views and a database you could use to retrieve elements and add them to your model. These elements could be sorted into categories such as supplier and material type.

Eastman said this system would lower the cost of design through its efficiencies in analysis and drafting. However, most architects at the time could not use the software, and it is not even known if any projects were made using the program. However, BDS was notable because it identified some of the biggest issues architectural design would tackle over the next five decades.

Evolution of Modeling Technologies

3D modeling in construction saw major advancements in the 1980s with new features like temporal phasing and graphical analysis. Technologies like this made it easier for professionals to model construction equipment in their building projects.

Temporal Phasing

In the early 1980s, several systems developed in the U.K. gained traction and were used for construction projects. One notable system was RUCAPS, the first program to feature temporal phasing. It was useful in the phased construction of Terminal 3 of London’s Heathrow Airport.

In 1988, the Center of Integrated Facility Engineering was developed at Stanford, which was a major landmark in the evolution of BIM. It led to the development of 4D models with time attributes for building.

Simulations and Graphical Analysis

In 1993, Lawrence Berkeley National Lab started developing the Building Design Advisor, which would perform simulations using an object model of a structure and its context. This software was among the first to integrate simulations and graphical analysis to provide information regarding the project’s performance. It could do this given alternative conditions concerning the project’s geometry, orientation, building systems and material properties.

Soviet Contributions

While all these developments were happening in the U.S., two prominent programmers from the Soviet Block would end up defining BIM as we know it today. Leonid Raiz and Gábor Bojár founded the two groundbreaking programs ArchiCAD and Revit.

ArchiCAD is notable for being the first BIM software available on personal computers. Revit, which was developed as an improvement on ArchiCAD, could handle more complicated architectural projects.

Revit

Revit revolutionized the world of BIM by using a visual programming environment to create parametric families and allow for a time attribute to be added to components. This allows a “fourth dimension” of time to be associated with your building model, enabling contractors to make building schedules based on these BIM models and simulating the construction process.

The Freedom Tower in Manhattan was one of the first projects to utilize Revit for design and construction schedules. It was built in a series of separate but connected BIM models that were tied to schedules, providing real-time material quantities and cost estimations.

What Is the Future of Modeling?

Although the concepts and technologies behind BIM are almost 30 years old, we have only begun to realize all the potential benefits of this growing industry. In the years and decades to come, possible advancements include the following concepts.

Project Quantum

The purpose of Project Quantum by Autodesk is to make BIM work in the cloud. As of now, applications are designed with one type of user in mind and have their own data formats. Autodesk wants to make some of its applications work together in a common data environment. This concept was demonstrated by opening up four applications on a single screen, with one of these platforms being Revit.

Each time a change was made using Revit, the change would appear in the other three applications. This data isn’t being translated to be compatible with other applications — it is instead transmitted to the other platforms via Quantum.

Live Sensors

With live BIM, we can make 3D models of buildings, bridges and roads using real-time sensors. We then combine the 3D model with environmental and physical data, resulting in the model changing color and shape based on these data. These live sensors can alert you of a problem before something actually goes wrong. By doing this, you can get a more comprehensive idea of how a structure behaves.

Work With a Data Modeling Expert

At Take-off Professionals, we create 3D data for layout and machine control. We also offer earthwork takeoffs with material quantities and dirt, cut and fill maps and mass haul analysis for roads and sites. Our cutting-edge process allows you to easily access high-quality data, providing you with the confidence to complete a project successfully. You can reach out to us for more information on working with us for an upcoming project by calling 623-323-8441, emailing us at info@takeoffpros.com or filling out our contact form.

3D Modeling for a Cul-De-Sac

3D Modeling for a Cul-De-Sac

American suburbia is practically synonymous with cookie-cutter houses, carefully manicured lawns and winding roads. Another staple of these types of neighborhoods is the cul-de-sac. These road designs have been used in suburban planning for the better part of the last century, increasing in use alongside American car-ownership. While cul-de-sacs are necessary in residential planning, however, they pose significant challenges for those involved in the planning. In particular, designing a 3d model cul-de-sac can be difficult due to the unique geometry involved. For this reason, we’ll cover the basics of cul-de-sacs in city planning, how to draw a cul-de-sac in AutoCAD and how Take-Off Professionals can help simplify the process.

What Is a Cul-De-Sac?

The cul-de-sac has been a common feature of the American suburb since the mid-20th century. This French term translates to “bottom of the sack,” and is used to refer to a dead-end street where the only outlet is the entrance. These suburban road designs are a direct result of the American motor age, purposefully created to allow for more spacious property facades while simultaneously encouraging slower car movements.

Cul-de-sacs were first used in 1928 in New Jersey, but gained popularity in the 1950s as car ownership boomed. The design gained further popularity as engineering studies on residential street safety encouraged more discontinuous street systems like cul-de-sacs. These studies found that such designs reduced the number of motor vehicle accidents compared to grid-based designs, and generally encouraged safer driving practices. Both features proved to be highly desirable for the more family-centered residential neighborhoods.

How Are Cul-De-Sacs Designed?

While it is simple to describe a cul-de-sac as a dead-end street, there is much more that goes into the design. Cul-de-sacs vary in road length but are typically designed with wider-than-normal road widths to allow cars to park along the sides while still allowing residents to enter and exit. These roads may be even wider if driveways are placed along the roadway. The defining feature of the cul-de-sac, however, is the wide, circular termination. This termination is where most of the residential driveways are placed. Cul-de-sac terminations are typically 100 feet or more in diameter, which allows cars to easily maneuver in and out of driveways and service and emergency vehicles to turn around.

Cul-De-Sacs in Neighborhood Planning

Homebuyers desire cul-de-sac-based communities for their safer streets, neighborly environments and lower crime rates since criminals tend to avoid confusing street patterns that make for more difficult getaways. While these features make cul-de-sacs more desirable for residents, planners favor them as well. Here are a few reasons why:

 

  • Reduced infrastructure costs: Cul-de-sac patterns require significantly less road and utility construction compared to grid patterns. Grid patterns require up to 50% more road construction and 25% more water and sewer line construction.
  • Improved topographical adaptation: While grid patterns blanket entire regions with invasive infrastructure, discontinuous cul-de-sac patterns can be designed to work around areas that may be more topographically challenging or ecologically important.
  • Decreased standards: Because they do not carry through-traffic, city regulations often do not apply in the same way to cul-de-sac-based neighborhoods as they do to grid patterns. As such, planners have less to worry about with regards to street widths, curbs and sidewalks.

 

These planning advantages make cul-de-sacs beneficial for home-buyers and a useful tool for neighborhood planners as well. For this reason, knowing how to design a cul-de-sac in 3D is a necessity for any construction design professional.

How Are Cul-De-Sacs Modeled?

Cul-de-sacs can be modeled with any AutoCAD software just like any other type of road. Using the data collected from a detailed topographical survey, planners can create a general plan for the roadways and cul-de-sacs. From there, professionals can then combine these plans into a detailed 3d model using AutoCAD software. Models should feature the cul-de-sac road, as well as any lots surrounding the cul-de-sac.

Cul-de-sacs can be modeled in several ways, but four primary features determine the overall shape and size of the cul-de-sac:

 

  • Centerline curve: The centerline of a cul-de-sac is the centerline of the street leading to the termination. This centerline can be curved or straight, dictating the overall shape of the cul-de-sac road. The centerline curve is typically determined by the topography of the area and should be placed in a way that allows plenty of room between the road and any topographical features that will not be altered during construction.
  • Terminal radius: The radius of the circular terminal is the distance from the center of the terminal to each side, and determines the overall size of the cul-de-sac’s terminal. For cul-de-sacs, this radius is a minimum of 50 feet, which results in a terminal that is 100 feet wide to allow plenty of room for emergency vehicles. The radius may be wider, especially if the cul-de-sac features a center island.
  • Termination placement: The termination of the cul-de-sac is designed to be a circular shape, but this circular feature may be placed in various ways. A symmetrical cul-de-sac is designed with the circular feature placed straight on the end of the centerline, resulting in the traditional match-head shape of a cul-de-sac. Alternatively, a cul-de-sac can be designed with the circular feature offset up to 90 degrees from the end of the centerline, resulting in a terminal that curves to one side.
  • Return curves: Placing a circular shape on the end of a rectangular road will result in sharp edges at the meeting points between the two shapes, which is undesirable for road construction. For this reason, the transition from the circular cul-de-sac terminal to the road is graded using return curves.

 

The above features are essential to know and consider while modeling for cul-de-sac neighborhoods and will come into play during the design process discussed below.

How to Design a Cul-De-Sac

Designing a 3D model cul-de-sac in AutoCAD is the most important step before initiating construction, as it creates a detailed plan to work from that can help streamline construction and minimize costly mistakes. However, cul-de-sacs are more difficult to design than normal roadways. One of the easiest ways to accomplish this model is by starting with a square and rounding off the corners to create a circle. This is a step-by-step guide for how to create a cul-de-sac with a rounded terminal using this method:

 

  1. Draw the road: First, create the road section of the cul-de-sac. In AutoCAD, this will appear as parallel lines with no clear termination. Be sure to place the road in a way that goes around topographical features that will remain in the final construction.
  2. Terminate the road: Draw a straight centerline across the end of the road where the circular terminal will be placed. Keep in mind that the terminal will extend past this endpoint by the termination radius, so allow enough room for the radius extending past this point. Make sure that the length of this centerline matches the diameter of the cul-de-sac, and place it according to the type of cul-de-sac you want to make. If creating a symmetrical cul-de-sac, place the middle of this centerline at the end of the road’s centerline. If creating an asymmetrical cul-de-sac, offset the new centerline as desired.
  3. Create the terminal base: Using the centerline drawn in the previous step, create a square section of road with a width that matches the diameter of the desired terminal. This should result in a square section of road that approximates the shape and size of the final terminal. At this point, double-check the placement of the road square to make sure that the terminal placement is correct. Symmetrical cul-de-sacs should be placed so that all sides of the terminal are equidistant from the centerline endpoint for the main road, while asymmetrical cul-de-sacs should be offset to one side.
  4. Create the junction: At this point, the AutoCAD software will detect a junction and should prompt you to create the return curves for the terminal. Enter the desired radius for these return curves — these should be fairly small, but keep in mind that the smaller the radius, the sharper the curve.
  5. Round out the terminal: At this point, you are ready to change the shape of the terminal to a circle. Use the road tools and select the section of road you have created. Depending on the software you are using, you should have the option to either change the shape all at once or to select each corner and set a radius for a curve. Make the changes according to what your software allows.
  6. Adjust terminal placement and junctions: From here, you can change the details of the terminal to match your desired plan. This may include moving the terminal from a symmetrical to an asymmetrical placement or vice versa. You can also change the radii of the junctions to create more gradual return curves.
  7. Add grading: Once the overall shape of the cul-de-sac is complete, you can combine this design with a topographical map or manually change the vertical leveling of the model to match the topography of the construction project.

The above guide represents a basic method for modeling cul-de-sacs in AutoCAD that practically any construction planning professional can use, with some adjustments depending on the specific software. But we have yet to address an important question about modeling for cul-de-sacs — why is it so important to model cul-de-sacs accurately?

 

Why Model Cul-De-Sacs?

Construction sites used to rely solely on surveyor stakes, heavy-duty equipment and quality operators, but 3D modeling has brought about significant changes in the way residential areas are constructed. 3D models create more accurate layouts that precisely show what is needed for a construction project and can identify potential problems before equipment breaks ground. This careful planning minimizes project costs significantly by reducing errors and maximizing labor efficiency. This is especially important for residential cul-de-sac construction, which is highly affected by construction costs and is significantly inconvenienced by lengthy construction periods.

On top of the cost benefits of implementing 3D models in traditional construction, 3D modeling can be used in implementing 3D model machine control. If you’re not familiar with this concept, machine control uses positioning sensors on equipment to give machine operators real-time feedback during construction. These sensors tell operators how to position buckets and blades as well as target grades, which minimizes error and maximizes construction site efficiencies. When implemented correctly with quality 3D modeling, machine control can help achieve the following:

 

  • Increased machine efficiency: By providing detailed feedback and instructions, machine control helps operators maximize machine efficiency and productivity.
  • Decreased operating expenses: Because the equipment is used more efficiently, construction projects require less fuel and maintenance to achieve the same results.
  • Minimized materials costs: 3D modeling allows for improved visualization of material usage, meaning that raw materials are used more effectively.
  • Reduced surveying costs: Using 3D models and sensors, the equipment provides feedback about grades to operators, reducing the need for ongoing grade checking.
  • Lowered labor costs: With more effective sensors, workers get real-time feedback that makes them more efficient, reducing the amount of labor needed for each project.
  • Minimized errors: Real-time feedback allows workers to see their progress as they go and catches errors early, reducing the need for reworking areas.

The key to achieving these benefits for cul-de-sac projects, however, is using complete and accurate 3D models. This is why construction companies are increasingly choosing 3D machine control modeling services to help with their neighborhood construction projects. If you’re looking for quality modeling for cul-de-sac projects, Take-Off Professionals can help.

 

Work With a Data Modeling Expert

At TOPS, our specialty is preparing 3D models for construction sites of all types. With over two decades of experience providing 3D models for the construction industry and a talented team of engineers and technical staff, we have what it takes to transform your data into what you need to achieve your goals. We produce approximately 1,000 machine control models a year, and our clients can attest to our accurate, timely and detail-focused service. Best of all, TOPS has engineers working in all major U.S. time zones, providing timely service across the nation.

In addition to our high-quality service and staff, TOPS provides a unique platform for our clients to upload all their project files, notes and related documents. With this secure and user-friendly program, our clients can communicate with us effectively while still being able to focus on their core business. It’s all part of our dedication to a hassle-free client experience.

Contact TOPS today to learn more about the benefits of our services and how we can help with your next residential construction project.

What is Mass Haul?

What is Mass Haul?

Mass haul refers to a calculation that multiples the volume of material with the distance that it’s transported during construction. It’s commonly used in construction and civil engineering projects as they often involve excavating and moving large amounts of earth. A mass haul movement is the transportation of this material from its original location to where it’s going to be disposed of, treated or used.

What Is a Mass Haul Diagram?

A mass haul diagram provides viewers with a graphical representation of the material moved. In particular, the diagram will showcase the amount of material that’s been transported along the centerline. It also displays the distance that the materials travel while being transported. In this diagram, you can often see grade points, overhaul and free haul regions and balance points.

Some of the key terms you should know to read a mass haul diagram properly include:

  • Haul: A haul refers to the transportation of your project’s excavated materials. The haul includes the movement of material from the position where you excavated it to the disposal area or a specified location. A haul is also sometimes referred to as an authorized haul.
  • Overhaul: When you get authorization to haul material farther than the original free-haul distance, the transportation of said material is called an overhaul.
  • Free haul: A free project’s average haul is referred to as a free haul.
  • Average haul: You can find the average haul using the mass diagram. The average haul is a specific area in a mass diagram. It represents how many cubic yard stations are between balance points divided by the ordinate of mass that the yardage gets hauled.

These diagrams are crafted using a mass haul view and a mass haul line. The mass haul view refers to the grid where the mass haul line is placed. The mass haul line refers to the overhaul and free haul volumes in fill and cut conditions that run along an alignment.

A project is in a cut region if the mass haul line rises. In contrast, if the mass haul line drops, the project is in a fill region. The diagram’s grade points and balance points will mark mass haul regions. Essentially, the mass haul line’s position in relation to the balance line shows viewers the movement of material.

On these mass haul diagrams, you can compare overhaul volume and free haul volume with the project’s grade points and the balance points.

Grade Points

Grade points are stations on a mass haul diagram that shows when a project design shifts from cut to fill. A grade point will reveal the lowest or highest point in a region of a mass haul. When the grade point in a mass haul region is the highest point, it represents where the project’s profile switched from a cut condition to a fill condition. The opposite occurs when the grade point is at the lowest point of a mass haul region. At this lowest point, the profile goes from a fill condition to a cut condition.

To measure free haul using grade points, you draw a horizontal line that is long enough to cover the span of the particular free haul distance. The line is placed so it contacts the mass haul line and runs parallel to the diagram’s balance line. The free haul is the volume of the area that’s inside the mass haul line and the horizontal line.

Balance Points

On a mass haul diagram, balance points refer to the stations where the fill volumes and the net cut are equal. These balance points can be found on the diagram’s balance line. More specifically, the balance points are stations where the net volume equals zero on the line.

To measure free haul with balance points, begin by duplicating the mass haul line and move horizontally. The distance it moves will be based on the free haul distance. If the project goes from cut to fill, you’ll shift the balance point to the right. You’ll move the balance point to the left when the project goes from fill to cut.

Uses of a Mass Haul Diagram

Mass haul diagrams are primarily used to provide a more accurate representation of the materials being moved. They give viewers key information about free haul, average haul and overhaul. For instance, you can calculate the free haul between specified balance points. Besides just finding the free haul between two points, you can find the free haul of the whole project.

They also have the very practical use of telling professionals and contractors the way project material needs to be transported. The diagram can showcase how much dirt a project needs to move. If you’re doing a significant amount of excavation or filling, the information that mass haul diagrams can provide is invaluable.

Additionally, you can use these diagrams to compare different proposals. Since contractors and designers can better understand where gross material movements will occur, these diagrams are perfect for showcasing how different designs approach the project. An accurate representation of the material needing to be excavated and hauled can help a company create an accurate quote for a potential client.

Using Mass Haul Diagram Calculations and Drawings for Constructing Roads

One of the major ways that mass haul diagrams are used is to assist with roadway design. Mass haul diagram calculations and drawings are crucial to helping designers find out how much earthwork is needed for a project. The earthwork that gets calculated takes into account the needed fill material to construct a roadway’s embankment and the existing earth material.

The ordinates on the mass haul diagram will be the sum volume of embankment and excavation. As such, road designers will hope that the initial ordinate is equal to the final ordinate to ensure the volumes of the embankment and excavation match. Designers use the diagram to make sure the total volumes of the embankment and excavation match.

If a designer notices that the initial ordinate is less than the final ordinate, the project has too much excavation. For projects where the initial ordinate is greater than the final ordinate, the embankment’s volume will be higher than the volume of materials you have to complete the embankment. This discovery will signal to a construction professional that they need more materials to complete the project.

During a highway construction project, these calculations are especially helpful. Construction professionals can use the calculations to balance the total amount of fill and cut of the highway project. By balancing them, contractors prevent having to spend extra money hauling more materials.

What Is Mass Haul Analysis?

A mass haul analysis is a feature often included in mass haul software. This type of analysis allows users to determine the haul distance and volume of a project’s net fill station ranges and net cut groups. To minimize the total volume-distance transported, a mass haul analysis program can calculate the best cut to fill movements.

How to Make a Mass Haul Diagram

Making a mass haul diagram starts with gathering a list of materials. Next, you need to have a simple line group and an alignment. On the x-axis, you’ll graph sample lines, which are sometimes referred to as stations. On the y-axis, you’ll graph your cumulative material volume. This cumulative material is usually earthworks. The balance line takes the form of a middle axis line, standing for zero cumulative volume.

There are a few different mass haul diagram software programs on the market that can help you generate a diagram. They each have their own processes for creating mass haul diagrams. These programs should allow you to do a mass haul analysis to see if you’re moving the needed amount of material, among other factors. For example, Autodesk’s mass haul diagram program, Civil 3D, is popular in the industry.

How Mass Haul Diagrams Can Help Companies Financially

Haul plays a significant role in determining the cost of conducting any earthwork for a project. A contractor or construction professional will need to create a bid price based on their estimation of their rate of haul, the equipment they need to transport a haul and the total amount of material that’s going to be hauled. By knowing information about the equipment you need and the rate of haul you can provide, you’ll ensure you cover your costs and make a profit.

One of the most important stats you’ll need to understand before you estimate your haul costs is the rate of haul. To get this information and the total haul, you should know where the project’s gross material movements happen at the worksite. As you attempt to determine this information, you can use a mass haul diagram.

An accurate and detailed mass haul diagram will give a company the information it needs to estimate the project’s total haul. For one, the mass haul diagram will indicate whether there’s a deficit or excess of material at various points in a project. The diagram also should give you a visual representation of the project’s cut and fill material. Detailed diagrams will also use curved lines to show how the material is moved during the project’s lifecycle.

With all of this information from a mass haul diagram, a contractor can figure out the most cost-effective way to complete a project. Since you won’t include the amount of material taken from borrow sources in the mass haul diagram, you can get an accurate take on your on-site materials and figure out the most cost-effective way of completing a project. In this evaluation, you can decide on haul, grading limitations, borrow source location, existing material placement and scheduling concerns.

The Benefits of Working With Data Modeling Experts

Mass haul diagrams are crucial for any time you need to transport materials on a job site. Working with Take-Off Professionals (TOPS) means you have Data Modeling Experts in your corner to assist with mass haul diagrams and analysis. We’re proud to provide our clients with Earthwork Takeoffs that feature cut/fill maps, dirt and material quantities and mass haul analysis for roads and sites. Along with offering these services, we also can create haul roads for your project’s entire life cycle.

There are many benefits to working with the data modeling experts at TOPS. Some of these advantages include:

  • Prevent mistakes: With our team in your corner, you get peace of mind. We’ll comb through your mass haul diagrams and ensure that there aren’t any problems. It can be a real headache if you realize you haven’t accounted for enough material once a project is already underway. Trust us to examine the details of your data to prevent mistakes from impacting your project.
  • Consistent service: You want someone you can trust in your corner. Your company may have a consistent style for diagrams, or you may need services completed quickly to keep up with your project’s demands. We’ll build your data in the exact way you require it, making it easy to read and in a form you understand. Additionally, you can trust us to keep up with your pace.
  • Cutting-edge technology: Staying up to date on the latest technology is absolutely vital in our industry. We’re always up to speed on the latest software and are continually improving our services. To prepare for every job, we consistently use four different kinds of software. We also have a broad range of experience with different programs, meaning we can use the best package to deliver exceptional results.
  • Expert staff: Our staff is filled with a variety of experts, from operators and grade setters to surveyors and engineers. They all have experience in their respective industries and can lend their expertise to different aspects of the project.
  • Focus: Our company focuses on data. We’re not here to sell you supplies, software or equipment. Instead, our only goal is to optimize your data and perform industry-leading takeoffs. This level of focus means we can devote all of our efforts to taking your data analysis to the next level, especially when it comes to evaluating a mass haul diagram.

Learn More About What Take-Off Professionals Can Do for You

Check out our many services to find one that works for you. If you’re interested in a mass haul diagram analysis, contact us today to discuss your options.

What is Point Cloud Modeling?

What is Point Cloud Modeling?

New technologies are always disrupting the construction and civil engineering industries. Point cloud modeling has existed for a while, but it’s becoming a major tool for contractors and engineers who seek more ease and efficiency when conducting land surveys. It accomplishes the same work with fewer resources spent — which is what every person wants from their business endeavors. But what exactly is a point cloud, and how does it help with surveying work sites?

If you want to learn how to use a point cloud for 3D models, this article can show you how it works — plus what you can gain from it.

What Is a Point Cloud?

A point cloud is a collection of many small data points. These points exist within three dimensions, with each one having X, Y and Z coordinates. Each point represents a portion of a surface within a certain area, such as an engineering work site. You can think of these points similarly to pixels within a picture. Together, they create an identifiable 3D structure. And the denser your point cloud is, the more details and terrain properties you’ll see within your image.

Creating and utilizing a point cloud puts a world of data within your reach, but you must know what to do with it after you generate it. This question can pose a problem for some surveyors — and others may not know how to create a point cloud to begin with. However, both of these problems have easy solutions. When you outline the goals you want to achieve from using a point cloud, you’ll know how to obtain your data and get the most value from it.

You can create point clouds by using two primary methods — photogrammetry and Light Detection and Ranging (LIDAR), which we will discuss in more detail below.

How Is a Point Cloud Created?

How do you create a point cloud when it involves so much detail and so many small points? The answer is typically a laser scanner. Site surveyors can create 3D models from point clouds by using LIDAR lasers. With the laser, you scan a chosen environment — such as a construction site — and the scanner records data points from the surfaces within it.

Once you have the complete point cloud, you can import it into a point cloud modeling software solution. At this stage, you can modify the data points for better accuracy. To see the point cloud in a 3D format that resembles your terrain, you’ll need to export the data from your modeling platform and upload it into a computer-aided design (CAD) or building information modeling (BIM) system.

Using Photogrammetry for Point Cloud Surveying

Photogrammetry is a common method for creating point clouds. With this technique, a drone takes numerous pictures of a construction or civil engineering site. Because the drone uses a camera, you’ll likely need to adjust its settings for the site’s environmental conditions to get the best results. Various angles are required to capture a full view of the landscape. Once all the images are captured, you can use a processing platform to overlap the photos.

By stitching the images together, you can develop a point cloud, create a 3D mesh and produce a complete 3D model within a CAD or BIM program. The process of filling in the gaps between the data points and creating a mesh is known as surface reconstruction. That’s why it’s essential to get as many data points and images as possible — you’ll have fewer spaces to fill in or reconstruct.

In contrast to photogrammetry, remote sensing — which is what LIDAR is categorized as — uses aerial vehicles to study a work site and create data points from it in real time.

What Is a LIDAR Point Cloud?

With the help of drone technology, you can use LIDAR to scan an area and record its data points to produce a point cloud. LIDAR uses infrared light laser pulses to measure distances. When these pulses reflect back to the sensor, it measures how long it took for the light to return. These laser scanners can emit up to 100,000 pulses per second, which gives an incredibly detailed view of the area being mapped.

Once you’ve created your LIDAR point cloud, it goes through a similar process of being transformed into a mesh and developed into a 3D model. Mounting LIDAR hardware onto a drone allows you to use 3D laser scanning to map any area you choose. Attaching the hardware correctly is essential — incorrect setup can impact the drone’s balance, which affects your data’s accuracy.

LIDAR and photogrammetry produce similar levels of accuracy. When choosing which one to use, it’s better to consider factors like how long it takes to set up the equipment and which method will be easier for you to work with.

How Is a Point Cloud Used in Site Models?

What is a point cloud in surveying? Land surveyors use point cloud modeling to create expansive representations of landforms where it would otherwise require tremendous time and effort. Even if your project isn’t huge, using LIDAR drones to collect data increases your efficiency and overall work experience.

Civil engineering sites can consist of roads, subways systems, bridges, buildings and more, which can have complex structures. Surveying these locations manually can stretch out a project’s duration and require a bigger budget, but technological advancements like point cloud modeling streamline the process. In general, new technology has significantly impacted civil engineering within the last few years. Additive manufacturing, smart tech and artificial intelligence are just a few examples.

Drone technology and point cloud modeling could also become essential elements of the connected job site. Tasks like geolocation, transferring as-built information and remotely monitoring work sites can all benefit from these two technologies. In turn, companies can improve employee productivity and safety and reduce their insurance and liability costs.

Point Clouds in Earthworks

Point cloud modeling techniques use drones, which have become increasingly popular for earthworks and construction projects due to their flexibility and efficiency. They can fill multiple roles within the building process — from the beginning to the end of any project. Mining, surveying and agriculture are among the many industries that have adopted drone technology for process optimization.

Here are a few ways that drones have shaped modern earthworks jobs so far:

  • Improved progress monitoring: Companies that commission earthworks projects don’t always have the time or resources to send people out to their sites to conduct regular checks. Drones enable them to inspect the progress by taking photos of the site and turning them into an orthomosaic. From there, they can use the orthomosaic to create a digital elevation model (DEM) and compare these daily shots to their final project plans.
  • Better worker safety: Manual surveying may require workers to walk up and down steep slopes or through rough terrain, which can prove dangerous if someone falls. If you put a drone in the field instead, you can capture data from afar without the injury risk.
  • Quicker cut-and-fill: Some companies use topographic surveys to do cut-and-fill comparisons, which can take days to perform on a large or complex work site. Processing the data adds more time to the schedule — but drones can accomplish data collection at faster speeds. Processing, importing and exporting this information using intuitive software becomes simpler.

Point Clouds Used for 3D Models

Constructing a 3D model can change in complexity depending on the building or landscape type and its features. Renovations or retrofits that must be done while the area is still in use add another layer of intricacy, but they are not impossible to do with the right tools. Laser scanners and high-tech modeling software solutions ensure that every possible object is identified and distinguished from the next.

For landscapes with complicated or richly vegetated terrain, it may be necessary to send a surveyor out to supplement any spots the scanner might miss. When you have your data points and begin the conversion from point cloud to 3D model, you’ll likely have more than one scan to work from. Similar to photogrammetry, you’ll need different angles of the same site to get the full picture.

Rendering the data into a 3D mesh organizes the points and sets a foundation that you can use to build a model. Exporting the point cloud creates a file that can be imported into a CAD or BIM system. What are the common point cloud formats? Depending on the software you use, you might see file formats such as:

  • PTS: PTS is an open format for 3D point cloud data. Because open formats are maintained by standards organizations, anyone can use them.
  • XYZ: XYZ is an archetypal American Standard Code for Information Interchange (ASCII) format. It’s compatible with many programs, but it has no unit standardizations, which can make data transfer more difficult.
  • PTX: This is another common format for storing point cloud data, usually from LIDAR scanners. It can only be used on organized clouds — no unordered ones. It’s also an ASCII format.
  • E57: This file format is vendor-neutral and compact. It can store point clouds and metadata from 3D imaging systems — like laser scanners. It’s also specified by ASTM International, with documentation in the ASTM E2807 standard. Additionally, it can store properties connected to 3D point cloud data, such as intensity and color.
  • LAS: This open format is designed for data obtained from LIDAR scanning, though it can also accommodate other point cloud data records. It combines Global Positioning System (GPS) data, laser pulse range information and inertial measurement units (IMU) to create data that fits on the X, Y and Z axes.
  • PLY: Known as the Polygon File Format, this type stores data from 3D scanners. It accommodates properties such as color, texture and transparency. It can contain data from both the point cloud and the 3D mesh.

Whichever file format you decide on, make sure your modeling software can convert your point cloud into one that’s compatible with your chosen CAD or BIM solution.

The Benefits of Point Cloud Modeling

Point clouds aren’t the only way to create 3D models, but they are incredibly beneficial for numerous reasons. Construction managers and civil engineers use 3D models for better machine control, improved accountability with project progress and true-to-life site layouts. Some of the perks of modeling include:

1. Efficiency

Uploading your point cloud into a photogrammetry platform lets you organize the data without the hassle of triangulating every point on X, Y and Z manually. The software does the work for you, which saves you hours of time you would have otherwise spent manipulating data. With these hours shortened, you can pull together the project details more quickly and begin your work sooner — which also means faster completion time.

Data collection is also faster because of the large number of points that can be recorded at once. A drone can sweep an expansive area in much less time than it would take for a surveying team to do the same.

2. Precision

Laser scanning and photogrammetry give quick and accurate results, transforming a living landscape into a detailed 3D model. Ground-based LIDAR can yield results that are accurate within a millimeter scale, while drone-based LIDAR is accurate from 1 to 30 centimeters. Its lasers can penetrate through dense vegetation for a more comprehensive site view.

Additionally, LIDAR often incorporates other features like GPS to ensure each data point comes with accurate information. Photogrammetry, too, uses Real Time Kinetic (RTK) geo-tags to ensure accuracy in recording the landscape’s form.

3. Savings

Because of the greater precision involved in site mapping with point clouds, you can plan a more effective budget for your projects. You can avoid going over your financial limit, and you’ll have fewer chances of running into any costly mistakes or unexpected expenses. Laser scanning also eliminates the need for manual surveying, which reduces the cost of hiring additional labor.

You’ll save money with these decreased or eliminated expenses, but you’ll also earn more on your projects. Your increased accuracy levels can lead more clients to trust you with completing their assignments, which boosts your reputation and encourages more companies to do business with you.

Work With a Point Cloud Modeling Expert

If you’re ready to incorporate point cloud modeling into your next engineering project, work with the experts at Take-off Professionals. We perform point cloud services and mesh conversions to help you process your data. Whether you’re working with a progress takeoff or an as-built, we can work with your information to provide the personalized results you need.

Working with a data modeling expert can help you save more money on your projects and finish tasks more efficiently. Conversion and processing require expertise and a fine-tuned eye for detail, which can lead to time-consuming mistakes if done on your own. By enlisting the services of our trained technicians, engineers and surveyors, you’ll receive results that have been refined by over 20 years of operation.

Fill out our form to learn more about how we can help you with your next job, or call us today at 623-323-8441. We do projects big and small, whether your point cloud consists of one construction site or acres of land.

What Is Photogrammetry?

What Is Photogrammetry?

For centuries, photogrammetry has played a critical role in our understanding of faraway objects and the Earth’s surface. Its uses have expanded over the years and have led to a powerful range of game-changing technologies in industries like construction, engineering, medicine and much more.

Photogrammetry gathers measurements and data about an object by analyzing the change in position from two different images. It uses things like perspective, advanced processing software and photo analysis to get the job done, but it can happen on the ground or from the air. In this guide, we’ll explain the different types of photogrammetry and how it can be used.

The Basics of Photogrammetry

The process of photogrammetry can vary, but the general idea revolves around gathering information about an object from photos of it. The photos are taken from different locations and angles to allow for precise calculations that help analysts gather the data they’re looking for. Typically, they use things like photo interpretation and geometric relationships to gather measurements. With the data gathered from photogrammetry, we can create maps and 3D models of real-world scenes.

The technology has been around for a long time and has been an important part of a variety of research in the last century. Its principles date back to Leonardo da Vinci’s research on perspective in 1480 — and many theories say it goes back even further. After the invention of flight and World War II, photogrammetric technology really increased, with powerful camera designs and new aircrafts built specifically for aerial photography and better camera positioning. All of the new inventions even put photogrammetry on the moon to map its surface during the Apollo missions.

If we break down the word, we can clearly see all of the parts that make up photogrammetry in play. “Photo” refers to light, “gram” means drawing and “-metry” refers to measurements. Photogrammetry uses photos to gather measurements with which we can create drawings and models.

What Is Aerial Photogrammetry? 

Taking aerial photos is one of the most common approaches to mapping out an area. In this process, a camera is mounted on an aircraft and pointed toward the ground with a vertical or near-vertical axis. As the plane follows its flight path, the camera takes multiple overlapping photos, which are then processed in something called a stereo plotter.

The stereo plotter is an instrument that helps determine elevations by comparing two different photos and conducting the necessary calculations. With the help of photogrammetry software, we can process this information and create digital models out of it.

What Is Terrestrial Photogrammetry? 

These images are taken from a fixed position on the ground with a camera’s axis parallel to the Earth. Data about the camera’s position, such as its coordinates, are collected at the time the photo is taken. The instruments used for terrestrial photography are often theodolites, though regular cameras are sometimes used as well. Terrestrial photogrammetry for surveying typically requires fewer resources and skilled technicians to accomplish, but it may take longer to cover a large portion of land.

What Is Space Photogrammetry? 

Moving out to a larger scale, space-based photogrammetry occurs with cameras either fixed on Earth, in an artificial satellite or positioned on the moon or another planet. In fact, photogrammetry was touted as a key part of space exploration even in the ’60s, and technological advancements have made it even more relevant. It can tell us about cloud patterns, create accurate maps of Earth and gather data about faraway planets.

Types of Photos

Since aerial photogrammetry is one of the most common methods, let’s take a look at how those photos get classified.

Typically, aerial photos will fall under one of two categories:

  • Vertical photographs: These images occur when the camera axis is vertical. So, if you put the camera in an airplane, its lens would point down to the ground for a birds-eye view.

  • Tilted photographs: Though the axis may be nearly vertical, tilts in the aircraft can cause an image to be unintentionally tilted in one direction. Within the category of tilted photographs, we have oblique photos, in which you can see the horizon line, and low-oblique photos, in which there is no apparent horizon. The classification depends on the level of tilt of the camera off of its vertical axis.

The lens of the camera can also offer a range of coverage. For instance, an ultra-wide-angle lens captures a larger field of view than a normal-angle lens. It would gather more of an image in its sights but could create distortion at its edges, depending on the lens and camera design.

When collecting aerial photos, operators capture many images in succession. These images need to overlap with each other, so the image processing software can identify the changes and understand where specific objects are placed. When it can capture those common items, it can more effectively stitch the photos together or gather data about their positions.

What Are the Principles of Photogrammetry?

This process can get complex, but it all comes down to the concept of triangulation. Triangulation involves taking pictures from a minimum of two different locations. These pictures create lines of sight that lead from each camera to specific points on the object being photographed. The intersection of these lines plays into mathematical calculations that help produce 3D coordinates of the specified points.

Triangulation is used in a wide variety of fields, from agriculture to military intelligence, but it is commonly associated with land surveying. Surveyors use theodolites and triangulation to gather the location of a point with the help of angle measurements. Triangulation networks can also help with a surveying system by maximizing accuracy.

It’s actually similar to the way our eyes work and create depth. Depth perception occurs when we see an object from slightly different angles, those angles coming from each of our eyes. Our brains process the two images and make them into a single image that we can comprehend in a process called stereopsis. This whole process is similar to triangulation.

Necessary Features

Some aspects are necessary for any photogrammetric model. These features include:

  • Tie points: Tie points are coordinates that can be linked across multiple overlapping images. Typically, these are features present in both or all of your photos. The tie points help the photo adjust with shared coordinates.
  • Ground control points (GCP): GCPs help to orient the image in relation to the Earth’s surface. They use known coordinates to position the image within the real world.
  • Bundle adjustment: The adjustment helps to remove any distortion within a set of images. It reduces errors from real and predicted image points.

Types of Photogrammetry

While we can classify photogrammetry based on the location of the camera, we can also break things down by the type of photogrammetry being conducted. These types vary based on the kind of data being gathered.

Two forms of photogrammetry that you’re likely to encounter are:

  • Interpretive: Interpretive photogrammetry is all about identifying objects and gathering significant factors from an image with careful and systematic analysis. Photo interpreters gather information about their subjects, such as characteristics and features, by analyzing and evaluating the photos carefully. The job may involve remote sensing technologies. Remote sensing combines photo interpretation with data from remote sensing instruments, like cameras on satellites or aircraft and sonar systems on ships.
  • Metric: In metric photogrammetry, the goal is to find measurements. A researcher may pull specific data and measurements from a photo with the help of other information about the scene.

Metric photogrammetry also covers planimetric and topographical mapping:

  • Planimetric mapping focuses on planes and includes elements outside of elevation, like roads, rivers and lakes. It ignores these topographic features, only focusing on geographic objects.
  • Topographical mapping does the opposite, revealing the shape of the land and its elevations and contours. It shows the Earth’s surface in comparison to a specific reference point, like sea level, and can be used for underwater surfaces, too.

Uses of Photogrammetry

The ways that photogrammetry comes to life can vary widely by collection method, data gathered, industry use and compatible technologies.

Some of the products that come from the process include orthomosaics, digital surface models and digital terrain models. An orthomosaic is essentially a birds-eye view of a terrain that adjusts for distortion and can span wide landscapes. Digital surface models and digital terrain models represent surface levels and elevation. Surface models include buildings and trees, while the terrain model gets rid of all of these features, showing the height of the bare earth.

The most common use for photogrammetry is creating maps out of aerial photos. It is cost-effective and accurate, allowing planning entities like architects, local governments and construction workers to make clear, informed decisions about their projects without spending months scouring the landscape. It is also very detailed and can provide an exceptional level of information about an area.

Photogrammetry makes its mark in an array of industries, from medical research to film and entertainment. Here are some of the places you can find it:

1. Land Surveying

We’ve already discussed the applications of photogrammetry in civil surveying, the results of which are used by many entities, including construction crews, governments, building planners and architects. All of the data gathered from photogrammetry inform them about everything from necessary safety measures to potential project results.

2. Engineering

In the world of engineering, drone photography helps to evaluate sites for construction, as well as  create perspective images and 3D renderings. Engineers can produce images of project results or previews, as well as analyze their current progress.

3. Real Estate

In the digital age, where 80% to 81% of millennials find their homes on mobile devices, creating attractive, accurate listings can significantly improve the buying experience and their understanding of the purchase. Viewers can see the home from all angles and get a clear idea of what they’re looking at.

4. Military Intelligence

Photogrammetry also plays a role in data gathering for military programs. Accurate geo-locational models with low processing times are necessary for understanding a landscape. Aerial imagery and photogrammetric technology can work together to create accurate 3D maps quickly without any human input.

5. Medicine

While you might not think to put the medical field in the same category as land surveying, the 3D models that come from photogrammetric technology come in handy for a variety of health-related uses. It can also work alongside remote sensing technology to help develop diagnoses without invasive procedures.

6. Film and Entertainment

Photogrammetry can play a big role in set design and world-building for a variety of films and video games. 3D modeling can bring unique objects to fruition in a virtual world, like cityscapes for action sequences and accurate historical elements, such as statues and buildings. One popular franchise that uses photogrammetry is the “Battlefield” games, which have an art style that works well with these 3D renderings and recreations.

In addition to world-building, photogrammetry can also assist with designing special effects and real sets.

7. Forensics

Photogrammetry also plays a part in crime investigation. It can help to document and measure precise data about a crime scene and determine what was physically possible. There are also many photogrammetric experts that can assist in the courtroom.

8. Construction and Mining

Project engineers and contractors can use accurate 3D models to monitor and plan their worksites. The information from a photogrammetric model can help create a smart worksite with sensors and safety features that improve the environment. These models work in tandem with connected vehicles.

9. Sports

Analyzing athlete movements can help coaches and researchers understand more about their activities. They can develop virtual training systems and learn about the physical effort that players expend by tracking their body movements. Topographical maps also come in handy for outdoor athletes, like hikers, mountain climbers, skiers and snowboarders. Mapping remote areas is often easier with the help of photogrammetric technology.

10. Agriculture and Forestry

In agriculture, aerial photos can offer insights into soil quality, irrigation scheduling, nutrition and pests. Farmers can adjust their planting schedules or adjust irrigation and fertilizers with this information. They can also use photogrammetry when assessing growth and crop damage after storms or floods.

Researching and managing forests becomes significantly easier with the help of photogrammetry. It can produce models to analyze various aspects of a forest, like timber volume and height, to better understand the development of a forest.

Work With the Data Prep Experts at TOPS

If you work in an industry that could benefit from photogrammetry or have another need for 3D modeling and photogrammetric data, Take-Off Professionals can help you get it. Here at TOPS, we create detailed and accurate surface models to help improve your work. Aerial photogrammetry is one of the fastest methods we use, which makes it especially helpful if you find yourself in a time crunch.

Data are our specialty, and we can assist with several tasks, including drone data point surface modeling, topographic file generation and custom photogrammetry services that meet your specific needs. Reach out today to learn more about how TOPS can take your project to the next level.

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