As the construction industry becomes more dependent on technology, early innovators Marco Cecala and Tom Pastuszak from TOPS are setting the stage for the future. Read more from The American Surveyor’s latest profile article, “It’s All About the Data: A Visit to Take-Off Professionals.”
TOPS engineer Mike Tartaglia walks you through the simple and easy task of taking detailed information from a PDF and placing it to create a working model using the Point Offset feature in Trimble Business Center (TBC).
The TBC platform is field-to-finish survey CAD software to help surveyors deliver high-accuracy GNSS data, create CAD deliverables and leverage full data traceability throughout a project’s lifecycle. TBC can do everything from sites and roads to point clouds and photogrammetry.
With the New Year well underway, I wanted to take a look and review the advances and advantages of current imaging technology as it relates to creating surfaces from LIDAR and Photogrammetry.
It appears that the more things change, the more they stay the same. Several parts of this world have made great strides while many remain slow to progress.
UAV platforms are cool, that is unless you have $38,000.00 in the air and it’s not responding to your request to come home. We need this device to do one thing; move a sensor in a predetermined pattern and image when requested and return safely for another use.
Prospective buyers have become focused on flight times, but the real number I always want to know is coverage and quality. A great camera with a proper lens can go high, fly for a short time and get the accuracy we are after. Once you know all the variables, the questions you ask will change.
Multirotors have idled in regard to advancement. Good motors, precision GPS and bigger more efficient batteries have allowed good flight times and safe operation. We use parachutes with our copters and feel comfortable sending them up.
Fixed wing platforms are split into two distinct camps, hand and wheel launch. The small, quick wings cannot carry good cameras and data quality suffers. The larger platforms need wheels and smooth ground but offer the benefit of carrying a larger sensor for better images. There is crossover in these types including hand launch/belly or parachute landing; the blurred line is offering some possibilities.
I am hoping this next platform gets proven soon, I like where it is going. The VTOL (Vertical Take-off and Landing) plane holds promise. Lift like a copter then fly high and fast with a big camera for a long time. Like any other platform, power is always the issue, to remedy this, some makers are putting gas engines to be used as thrust motors and even generators. I think we will have something worthy by year end.
At this moment, the best solution for aerial topography is a full-frame sensor camera and a good lens. We can obtain good accuracy on a consistent basis. There are some improvements on the horizon that will help things.
When a drone flight is not possible due to regulatory restrictions, our trade partner Doug Andruik at Syn-Geo had created a two-camera pod he puts on the strut of a Cessna and effectively does close range photogrammetry with a full-scale aircraft. A great solution for large acreage or no drone zones.
We are all waiting until LIDAR becomes effective for use on a UAV. Several versions are out with fair accuracies and high price tags. Development is happening daily because of the great potential of the application. I’ll look at these and report as they become available.
One of the best things to come along for improved close-range photogrammetry is precision GPS. The Applanix chips (Trimble) have made geo-referencing images more accurate and easier. When an image is correctly geo-tagged, post-processing is quicker and the resulting 3D information is more accurate. Combine this exacting geo-tagging and good images and accuracy gets much better. This makes our fieldwork more efficient and the results in the office better. In my opinion, this is the go-to solution; for now.
Pix 4D is still the easiest post-processing software, my issue is the same data-set run multiple times yields different results and residuals. As with any processing of imaging data, check to many ground control points to verify accuracy. UAS Master from Trimble is a robust application with the ability to fully incorporate precision GPS orientation from the Applanix chip. I use the software on a regular basis but am hesitant about training users. When you know how all the aspects of the program interface you can do some great things. When first learning post-processing, there are too many variables in the software to “just click a few icons” and get a result like in other applications. That Power can be a pain to use sometimes. Rumors are that there will be some easier workflows coming in future versions, I’ll keep you updated.
Right now the best way to get reliable, consistent data is to fly a full-frame mirrorless camera with a high-quality lens using copter with an Applanix chip and post process in the software of your choice.
Always collect a TON of control/checkpoints so you know how good the results actually are. We earn our money back in the office slowly going over data, cleaning up the point cloud and shipping the client a good surface.
Proposal for presentation at Site Prep Tech
Marco Cecala, President, Take-off Professionals, Inc.
The recent advances in technology for use in civil construction are impressive. The broad appeal of GPS, LIDAR, lasers, total stations and computers have provided the contractor with many opportunities. Contractors have embraced these advances, but not without difficulty during the learning process. Many have made technology a profitable part of their business, while others question the advantages.
This interactive presentation will answer questions and provide a strategy for establishing or streamlining your use of technology.
- Brief overview of current equipment types. GPS, Total Stations, LIDAR and field computers.
- Best use for each type of technology.
- What to buy, and when.
- What training options are available and their differences.
- How to take full advantage of dealer, manufacturer and independent training.
- How to identify key staffers for leading the technology push.
- How to stay current with training as it relates to hardware and software upgrades.
- What to expect from the technology.
- Implementation; gradual or all in?
- Responsibility chain when using technology.
- How the high tech job site differs from traditional grading.
- The connected job site, how it can help profitability.
- How technology changes job dynamics.
- How electronic data affects a site.
- How to effectively manage data from the office to the field.
- Meeting requirements for the use of technology.
Marco Cecala is the President of Take-off Professionals. A Civil engineering consulting firm based in Phoenix, AZ. As the nation’s most experienced and largest firm of their type, they are uniquely qualified to work with contractors and engineers on projects of any size.
Their business involves preparing 3D models for machine control, quantity take-offs, training and consulting.
If you have never had the misfortune to deal with the difference between US and International feet, consider yourself lucky. When the issue presents itself, it can make things difficult to understand. No worries, the curtain will now be pulled back and the mystery solved.
First a bit of history, this will be abbreviated to keep you awake. The United States joined the Treaty of the Meter in 1875. It took the group 5 years to redefine the metric system, which made the length of the yard measurement used in the US at that time different from that used as the standard dictated in the Treaty of the Meter.
In 1960, the US changed the yard to .9144 meters exactly. This shortened the length of the new US Yard by 2 part per million. We will go over what this means in a moment, for now here is the conversion factors. US to International feet, multiply US feet by 1.000002000004000008000016000032 (approximately) to get International feet. Yes, that’s five zeros followed by a 2 and a lot more zeros. In other words not a lot. To go from International feet to US feet, multiply International feet by .999998 (exactly).
The take home message above is two parts per million. In other words, if you were working on a 2 million foot long road, (378.79 miles) your error from end to end would be 2 feet. My point is that using either system will not affect your job. If you are using International feet and the job was surveyed in US feet, you will be OK. With exceptions, read on.
I will use a simple but powerful example to explain the issue. Our imaginary job has a corner point of N 2,000,000 and E 2,000,000. The surveyor localized in International and I build the job in US feet. The corner point I mentioned is the same coordinate value for both of us. It does not matter what coordinate system I use to localize the site with my rover. I am going to occupy the points staked by the surveyor. This includes our subject 2 million by 2 million coordinate. The job will fit and perform fine. I refer you back to the fact the difference in these two systems is 2 parts per million.
With the above information known to you, how can someone ever have a problem with the different systems? In a word; conversion. Let’s use the coordinates above. The plan notes read the job was built in International feet, we decide to make it US feet. Applying the conversion we get the following;
2,000,000 x .999998 = 1,999,996.00 In this example we can easily see the 2 parts per million. Our job is now 4 feet off to the north as well as the east. All you need to do is move the job and verify the rotation of the job from our 2 million, 2 million point. We always check at least 3 points. Here is the hard part to understand. You effectively shrunk the job, why won’t this affect the actual size of the site? I refer back to the 2 parts per million factor.
Let’s say you are on a big site, a big truck merchandise transfer facility off an Interstate highway. The job is a mile across. How will the job size be affected by the conversion? Here is the math.
1 mile, (5,280 feet) x .999998 = 5,279.98944 That translates to a hundredth of a foot over a mile. This difference is impossible to see on paper, or in the field.
What do you need to do? Here are the guidelines for success;
- Try to use the native units the job was designed in.
- Never convert units, just know what you have and what coordinates the site was localized in.
- Make a note of at least 3 points that you can find on the CAD file and the site. Refer to these and verify they are in line with each other.
- When in doubt, ask somebody to verify. A question now is cheaper than a screwed up job.
I wrote an article a while back about the difference between US Survey and International Feet. You can read it here.
I have received many questions regarding what can happen to a job and how to tell what units you are in. To address this, I will first go through the correct way to do things; then go through a routine that will ignore the units and get you working.
Here is how you should go about localizing a project.
- Contact the surveyor and verify the unit type being used on the project. US Survey feet or International feet.
- States differ. The surveyor can even choose to use something different than the state recognizes. Make sure you get on the surveyors page.
You will need to start from the top down in order to make sure the job is in the correct units, but read on; it’s a mine field out there.
In the Office
- Always select, write down and refer to at least 3 points that can be located on the paper plans, the CAD files and the job in the dirt. Share these with the surveyor or ask them for three points they use for “check in”. Check in is a group of points that ends up getting memorized because you check into them several times a day, especially first thing in the morning.
- Verify the job in in the correct units; US Survey or Int’l. Draw these Check In points on the screen in the program you are using to build the data and verify that they are in the right spot. I previously mentioned the points need to be related to lines on the CAD, plans and ground. With that being the case, you will now see the points right where they belong.
- The image shows a cluster of points. Make sure there are points scattered around the entire job. This serves two purposes; if you check into the extents of the job instead of one corner, you’re assured of the orientation. Secondly, you won’t have to walk/drive so far if you spread out the information.
- At this point you have a job set to the correct units and the check in points are where they are supposed to be. Export the data from your program in the correct units and bring it into the transfer software. This refers to the intermediate software that converts CAD data to a format readable to the field equipment.
- Many software vendors are eliminating the step of the additional software saving you one more chance for things to get fouled up.
- The data can now leave the office; it is in the correct units and properly oriented.
In the Field
- Localize with the correct units and verify residuals. With a good localization, you can now confidently install the job files.
- Upon loading the data, take the rover and head to at least 2 of the check in points at opposite ends of the job to verify you have everything set right.
- You have just verified that your job is in the correct units and oriented correctly. You may proceed to work on the job after loading and verifying each machine.
- You are only as accurate as your last occupation of one of the Check In points. We will now discuss why this is so.
What causes problems
Technology and construction are constantly improving, as we learn more we take that knowledge and put it to use in the field. As an example; a grade checker reads my article linked above and decides the job needs to be in US Survey feet. Drilling through the menus he changed the setting and went back to work. Luckily things looked funny and he had the good sense to figure out the error of his ways before ruining previous work. Crisis avoided and lesson learned.
I am all for doing things by the book as described in this article. I also spent many years in the field and understand the need for production. Here is what you need to know in order to make things work regardless of the units used.
The most important thing to remember is the difference in US and International feet is 2 parts per million. With a job localized to state plane coordinates of a N1,000,000 E1,000,000 in US feet and the site loaded in the incorrect units, it will be off by about 2 feet.
If this happens, the job can be moved to correctly occupy the Check In points and work proceed; here is the reason:
Even though the jobs units have been changed, a site or road is not big enough for the error to be noticed. As an example, if we were on a road that was a million feet (189 miles) and we moved the job to set on the start station, the road would be 2 feet off at the end. I know this is never going to happen, but it illustrates the error encountered when the job is correctly placed on your localization and Check In points. Any single site, no matter how large will remain unaffected. Larger jobs always have multiple base station locations and localizations which zero out the error on every new setup.
Tips for Success
- Start from the top down with data in the correct units. The same units the surveyor is using.
- Have shared Check In Points used by you and the surveyor. You are only as good as your last Check In, do it first thing in the morning and throughout the day.
- Immediately stop when something does not look right.
- Even though you can muscle the job into working by moving it. It is always best to start correctly. Your results will be better and you will sleep easier.
Part 3 of “GPS is underutilized”
When spring rolls around, road construction gets into full swing. Road contractors were early adopters of technology and continue to drive the development of new applications and equipment. Among them are laser augmentation for vertical accuracy and the automation of paving and curb machines. In an effort to improve efficiency, the contractor needs to use technology wherever possible. This includes preparation of dirt grades and the application of subgrade materials.
Standard Road Subgrades.
When working with a site, it is easy to “dial down” the surface in order to grade to the top of dirt, compacted subgrade, and rock. This vertical offset works well, even though it just lowers the entire site the set amount.
This drawing shows 3 layers that can be installed using a vertical offset. With a well-prepared subgrade, it is possible to pave using sonics and obtain good results in a basic parking lot.
For many road jobs, the subgrade is easily set with vertical offsets. A typical basic road design for urban rehabilitation work is one example. Here we see top of dirt and prepared native subgrade that can be done with vertical offsets.
The subgrade extends beyond the road/curb finish. To make this easier to model, just the finished surface can be built. The equipment operator can run the blade down the road section and use sonic and cross slope or a horizontal machine offset to pick up the additional 2 feet.
Extended Road Subgrades.
Where side slopes are built into a roadway, another layer of difficulty is added. The subgrade hinge represents the intersection of the side slope and the projection of the subgrade. It is shown in this drawing inside the red circle. Refer to the video for a better understanding. There are two ways to accomplish the production of the subgrade hinge, office calculations or field adjustment.