Using Aerial LiDAR for Infrastructure Surveys
The history of Tuck Mapping Solutions and LiDAR began in the 1990’s with our firm flying a LiDAR system for Airborne Laser Mapping. Dave Ward had a project for a developer near Williamsburg, Va. It ran along Interstate-64. He asked us to fly his system because our Piper Navajo 310 had a cargo door that allowed him to put his mainframe computer in the passenger compartment with the 5 kHz Optech LiDAR system. This LiDAR was the first system produced by Optech in Canada.
Since the project was adjacent to Interstate-64 and the flight lines encompassed parts of the interstate, I thought it would be an interesting experiment to show the Virginia Department of Transportation (VDOT) how accurate we could map the interstate boundary. This project was completed successfully and the final report was submitted to VDOT. This project ignited their interest in using LiDAR for highway design.
Coping With Nature
After we had successfully flown the Williamsburg project, Tuck Mapping was working on a location survey for US Highway 58 near Damascus, Va., and a portion of the area could not be mapped using aerial photography. We were trying to determine how we could complete the mapping in an effective way. The area was covered in mountain laurel, making it difficult to see the ground using imagery for mapping and cross sections. The VDOT Surveying Department welcomed the opportunity of testing the LiDAR system’s functionality/capability under these difficult circumstances.
John Chance was flying a railway system in North Carolina when I called him to see if they would be interested in flying this project. After discussing the project area and challenging environmental circumstances (i.e. thick undergrowth and steep terrain), they agreed to fly the area but could not guarantee the results. Chance used their helicopter-based LiDAR system to acquire the data in the area where we could not map. The mapping was very successful and it showed the highway department that LiDAR could be a valuable tool for their mapping projects.
We developed a report for the highway engineers on the procedures that were used during the mapping project. We also briefed the Transportation Research Board on our results. We could achieve 6-inch vertical accuracy at that time, but I was determined to get accuracies closer to 2 inches and be able to use LiDAR for highway design. I was told by many people in the mapping industry that my goal was impossible. I made up my mind that they were wrong.
Packaging a Solution
Tuck Mapping had been utilizing the FlyKin software that was developed by Paul Mrstik, PE, OLS from Mosaic Mapping in Ottawa, Canada for our airborne mapping solutions. I was in a school sponsored by Leica at the camera workshop where Mrstik was teaching us techniques of the airborne solutions. He knew I had some helicopter experience and asked me to review some of his ideas on LiDAR. He wanted to place a system in the helicopter to acquire high accuracy data for corridor mapping projects with better accuracies than the current aircraft-based systems. I agreed to work with him on the project.
After the system was put together, Mrstik flew a portion of the Cherokee Indian Reservation in North Carolina for me. The LiDAR system was an extension of the Mosaic working laboratory, and the wiring in the lab was simply put into a pod and placed under a Hughes 500 helicopter. The system worked as designed and we achieved very good results on the project. We then worked with Mosaic to organize the system in a pod with detailed drawings and ultimately obtained FAA approval for the system. We mounted it in our Bell JetRanger and made the system portable enough so that we could fly missions in the United States.
Following a mission, we would remove the system and Mrstik would take it back to Canada to complete projects there and overseas. We looked for mapping opportunities in the U.S. and when we found them, we secured the contract and completed the ground surveying. Mosaic would then bring the system to the U.S. and we could install it in our helicopter in a matter of several hours. The missions were flown and the system was removed for its trip back to Canada.
We continued this process for several years and Tuck Mapping learned from Mosaic how to manage the projects. I have the utmost respect for Mrstik's wisdom and the knowledge he has provided me about LiDAR and how to improve accuracy. In 2000, the Mosaic Mapping LiDAR system used in our helicopter included a RIEGL LMS-Q120 scanner, which had an output of 10 kHz and a maximum range of approximately 400 feet. In 2003, I wanted to put together a system that combined a metric camera with the LiDAR for simultaneous acquisition. Mrstik had mounted a standard digital camera to the platform so we could have LiDAR and imagery from a non-metric camera.
Scanners and Digital Cameras
When Applanix purchased a camera system to put with their POSTrack system, I asked Joe Hutton, MASc, PE if he could couple the Applanix camera with the RIEGL scanner. He said no, but he would couple my scanner to his digital camera and the POSTrack system. I agreed and we were able to couple the systems successfully. In 2003, we purchased a RIEGL LMS-Q240 scanner, which had an output of 10 kHz. The scanning rate resulted in approximately 4 to 6 points per square meter. We teamed with RIEGL and Applanix to build the EagleEye Mapping System that combined a medium format camera with the LiDAR system for simultaneous acquisition. The system was guided by the POSTrack guidance system and was very successful. We decided to purchase a second helicopter and build an identical system. We purchased a Bell LongRanger and put the duplicate system in it. These two systems were flown for several years on many types of highway, military, development and other survey projects.
In December 2007, we purchased the RIEGL LMS-Q560, which was a full waveform scanner with an output of 240 kHz. My staff and I were the first customers trained on the use of RIEGL’s RiPROCESS software. We went to the factory in Horn, Austria, and trained at the factory with the technicians that developed the software. The technicians at the factory provided insight on how the software was developed and methodologies on how to plan our missions to obtain the best results out of the scanner. This new LMS-Q560 allowed us to fly higher and acquire a much denser point cloud. Our average density with this system has been approximately 30 to 40 points per square meter at an airspeed of about 50 to 60 mph at 500 feet above ground level (AGL). We can fly this system up to approximately 1,200 feet before we start to see a drop out of pulses hitting the ground.
This was also our introduction to the full waveform scanner and the benefits of digitized pulses. Our LMS-Q560 is still in operation today and has been a steady workhorse for our company. To my knowledge, our system has never been down for maintenance within the past 10 years and it is still a very accurate system. It has averaged a vertical accuracy to less than 0.1-foot on every job in the last 10 years.
Working the Angles
In March 2010, we purchased a RIEGL VQ-480 scanner with an output of 300 kHz. This scanner was installed in an azimuth mount on our Bell LongRanger helicopter. With the VQ-480, we can acquire approximately 30 to 40 points per meter on the ground at 800 feet AGL at 60 mph. This scanner is paired with a Leica RCD30 four-band digital camera. The reason we purchased this system was to replace our second system containing the RIEGL LMS-Q240. This scanner was also a waveform scanner which processed waveform data real-time, and the data is extremely clean. We installed the scanner in the pod of an azimuth mount at 8 degrees. The 8 degrees came from research that Tuck Mapping had done for the National Geospatial Agency (NGA) on the best scanner angle so the faces of buildings, power poles and areas under vegetation could be captured for enhanced bare-earth surfaces. This system is still our primary system for highway and power line mapping.
In September of 2010, we acquired the RIEGL LMS-Q680i that outputs 400 kHz. In 2016, we paired this scanner with our new 195-megapixel Vexcel Falcon Prime digital 5-band camera with impeccable radiometry. We can acquire high-resolution digital imagery and high-accuracy LiDAR data simultaneously, as we have been acquiring in the helicopter for many years. This scanner is mounted in the baggage compartment of our Piper Navajo 310 twin engine aircraft. We can fly fast and high and still get great accuracies that rival the accuracies from our helicopters. When dense point clouds (greater than 20 points per square meter) are not required, this system is the most economical system to fly. We can ferry the Piper Navajo (at approximately 170kts) long distances and collect imagery for large sites at a very cost-effective price. When we are providing orthophotography or planimetric mapping for large tracts, we are now able to collect LiDAR data for the DEM, which is more accurate than what the compilers can compile from the imagery. Our only issue is that we have a difficult time collecting the necessary point densities and pixel resolutions at the same altitude. Therefore, we must compromise and gather more or less data than necessary – or we have to fly at two different altitudes. We came up with an excellent solution to this issue.
In December 2017, we purchased the new RIEGL VQ-780i scanner with an output of 1,000 kHz. In case you do not have a feel for 1,000 kHz, it is 1,000,000 points of output per second. This new scanner allows us to meet both the specs of the imagery and the specs for the point density while flying at one altitude. This scanner is replacing our RIEGL LMS-Q680i that has been installed in the Piper Navajo twin engine aircraft. This combined system has allowed us to collect 3-inch pixel imagery and approximately 0.71 inch vertical accuracy at 4,000 feet AGL and 6-inch pixel resolution and 2.5-inch vertical accuracy at 8,000 feet AGL. The new RIEGL VQ-780i not only collects high density, high resolution data, it also provides for the processing of the full waveform data during the flight. This reduces the post-processing time of the point cloud after the flight. The new RIEGL VQ-780i system provides twice the point density at the same altitude (compared to the RIEGL LMS-Q680i). Or, said another way, we can fly twice as high and cover four times the area with the same density of points as we could with the older RIEGL LMS-Q680i. By pairing our new RIEGL VQ-780i with our Vexcel Falcon Prime, we can create a high resolution/ high accuracy product that allows our clients to have the best of both the photogrammetry and LiDAR worlds.
|Altitude||Piper Navajo Panther Speed Knots||RIEGL VQ-780i Points Density Per m²/Pass||Vertical Accuracy||Vexcel Falcon Mark 2 Pixel Resolution|
|2000 ft (610 m)||125||15.0||1.12 in (2.84 cm)||1.4 in (3.6 cm)|
|3000 ft (914 m)||125||10.0||1.35 in (3.42 cm)||2.1 in (5.4 cm)|
|4000 ft (1220 m)||125||8.0||1.50 in (3.81 cm)||2.8 in (7.2 cm)|
|5000 ft (1524 m)||125||7.0||1.76 in (4.47 cm)||3.6 in (9.1 cm)|
|6000 ft (1828 m)||125||5.0||1.76 in (4.47 cm)||4.3 in (10.9 cm)|
|7000 ft (2134 m)||125||3.0||2.00 in (5.08 cm)||5.0 in (12.7 cm)|
|8000 ft (2438 m)||125||2.0||2.00 in (5.08 cm)||5.7 in (14.5 cm)|
Additionally, Tuck Mapping is building a new LiDAR system that will combine the RIEGL LMS-Q560 in a pod with the RIEGL LMS-Q680i. The RIEGL LMS-Q560 will be installed at a 10-degree angle allowing point acquisition on building faces, the sides of power poles and underneath vegetation canopies (where applicable). The RIEGL LMS-Q680i will be set at nadir and scanning simultaneously with the RIEGL LMS-Q560. We will have two channels operating together for enhanced coverage. This new system will be flown in our Bell JetRanger at 800 feet AGL. We will have a resultant point density of approximately 45 points per square meter while traveling 76 mph. In a single pass, this system will acquire the same amount and type of data that normally requires dual flights for a corridor mapping project.
Tuck Mapping has been utilizing the RIEGL family of scanners for nearly 20 years. Dr. Riegl and his staff have provided our firm with an enormous amount of technical support since we began assembling systems with their scanners 20 years ago. Tuck Mapping has assembled several custom-built systems to fit the desired outcome for our clients. We have performed research projects for the U.S. Army Corps of Engineers and for the National Geospatial Agency, which have been completed successfully, and we developed a great deal of knowledge in the process. This experience and technical expertise has allowed Tuck Mapping to develop systems and methodologies that are accurate and affordable for our clients.
Additionally, the Vexcel management team has begun to involve us in some of their manufacturing plans for future camera systems. We have agreed to perform several research projects using our combined system (the Falcon Prime and VQ-780i) to provide knowledge on how the systems can be improved. Our goal at Tuck Mapping Solutions is to find the best solution to meet the needs of our clients. If a solution is not commercially available, then we work to engineer a new solution to meet today’s market demands. Tuck Mapping cannot do this on our own. That is why we rely on our manufacturing partners to work with us for solutions that are not commercially available. This forward thinking on the part of our staff and the manufacturing partners has helped us become a leader in the implementation of new equipment to our mapping industry.