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.