Another Notch in the Technology Toolbox
Is a drone the best way to collect data for your project? How about a Robotic Total Station or RTK GPS? Or perhaps mobile or aerial LiDAR is the way to go.
McKim & Creed has always been an early adopter of technology, both in hardware and software. At times we have been accused of being on the bleeding edge, but we believe that using the right tools for a specific task under specific conditions can have many benefits. Customers benefit from the increased efficiencies, which lowers their cost. McKim & Creed benefits from repeat business, as we have developed the reputation of providing a cost-efficient product that meets the client’s objectives in regards to scope budget and schedule.
This year we’ve tested our newest technology— unmanned aircraft systems (UAS), a.k.a. drones—to see how its capabilities compare with conventional methods and to help identify the pros and cons of the system where, what types of projects it makes sense to use them.
We focused on two types of surveys: a landfill volumetric survey and a beach monitoring survey. Both are typically conducted using fixed-wing aerial photogrammetry, or aerial LiDAR and/or conventional ground surveying.
UAS for Landfill Survey
For our volumetric research, we conducted a case study in which we employed UAS to survey a 60-acre land clearing and inert debris landfill. McKim & Creed teamed with landfill engineers Garrett & Moore, Inc., who typically rely on aerial mapping data to perform volumetric analyses. Using a 3D Robotics Solo platform equipped with a Sony QX1 camera, McKim & Creed captured the data in less than an hour. The data was verified onsite, and point cloud creation was completed in less than 24 hours. This allowed us to extract planimetrics, contours and volumetrics faster than with conventional ground survey, aerial photogrammetry or LiDAR.
The project was designed to meet ASRPS Positional Accuracy Standards for Digital geospatial Data (2014) for a 5cm RMSEz vertical Accuracy Class equating to NVA =+/- 9.8 cm at 95 percent. Our results were twice that, at 2.25cm Vertical RSME equating to 4.45cm at a 95 percent confidence level. This is accurate enough to produce a ¼-ft contour interval. We set eight control tiles prior to the flight and collected 12 independent ground truthing shots randomly throughout the project limits. These were compared to the post processed 3D surface.
The case study indicated that UAS can provide significant cost savings while exceeding the accuracy specification for this type of survey. Our results show that on average, using UAS for landfill surveys is approximately 10-40 percent cheaper than conventional ground survey based on the condition of the site, 30-40 percent cheaper than aerial photogrammetry, and 40-50 percent cheaper than LiDAR.
UAS did have some drawbacks, however. Data was difficult to capture in highly vegetated areas. In those types of conditions, it may be necessary to supplement UAS with ground survey.
UAS for Beach Monitoring
On May 16, during National Hurricane Preparedness Week, we teamed with geospatial software giant Esri to conduct a proof of concept for local, state and federal public agencies. We used UAS to collect topographic data for beach monitoring surveys, and then compared the data with conventional land survey data collected by the local county and with terrestrial lidar data collected by the US Army Corps of Engineers. The data was compared for accuracy, cost and delivery time.
McKim & Creed again used 3D Robotics’ Solo platform, along with SiteScan software, for data collection. Esri processed the data using its Drone2Map software.
The result? The data comparison showed that, in the correct environmental conditions such as open beaches or moderately vegetated berms and basins, UAS outperforms conventional services by producing a more detailed digital elevation model (DEM) more quickly and at a lower cost. In fact, we estimated a 60 percent savings in time and cost, when compared to conventional techniques.
One other very significant benefit specific to coastal monitoring is the ability for the UAS team to collect massive amounts of data in a short time. In the event of a major storm, a UAS survey can be accomplished just days before an approaching storm and again immediately after the storm subsides. The site will be well documented with a 3D surface and high (1.5cm) resolution ortho photography.
Other Innovative Data Collection Technologies
Next generation Robotic Total Stations have joined several of our geomatics crews in the field this year. The robot enables us to use one- or two-person crews, rather than two- or three-person crews. The instruments feature integrated cameras that allow the photography to be georeferenced and used for mapping. This is a huge benefit to the CAD designer when drawing a map, and is a valuable QA/QC tool when checking for missed information.
Mobile LiDAR is one of the safest methods of data collection around, provided you’re surveying in an area that’s navigable by a motorized vehicle. Our MoDaC Mobile Data Collection™ system collects up to one million points per second while traveling at posted speed limits. For urban highway design projects with multi-lanes and high traffic areas it is hands down the go to system. The post processed data is accurate to within 0.05-ft.
The system is highly flexible as well, and can be transferred to an ATV or boat to collect data in less accessible areas.
Like its mobile counterpart, airborne LiDAR offers the benefits of fast, safe and accurate data collection for “wide area” mapping and utility corridor mapping. Our acquisition platforms and sensors include fixed wing and helicopter-based airborne LiDAR, along with high-resolution aerial photography using both RGB and infrared digital cameras. The applications for this technology are widespread, and include electric distribution and transmission, roads and railways, aviation, telecommunications, oil and gas, water, forestry and agriculture and local, state and federal government.
Surveying at the Speed of Innovation
Surveying technology is improving all the time, but our goal is not just to keep up with the latest and greatest. At McKim & Creed, we thoroughly test these technologies and compare the results with other tried and true methodologies to ensure that we can offer the right tool for your project.
The proof of concept was conducted at Wrightsville Beach, North Carolina. Several local, state and federal officials were present.
Two sites were surveyed: a major disposal area of dredged material and …
… north and south rock jetties.
McKim & Creed placed temporary photo-identifiable targets on the beach and surveyed to georeference the UAS flight. Blind checkpoints were also collected at the site to independently verify the accuracy.
Shown here is the DEM with contours from the landfill site that was surveyed using UAS.
The surface model created from the UAS-collected data exceeded expectations.
A north-south flight pattern was chosen with a forward overlap of 78 percent and a side overlap of 60 percent. The mission was flown at 400 ft. above ground level (AGL), giving us a ground sampling distance (GSD) of approximately 3.5 cm. Due to temperature and wind conditions, we conducted two flights to ensure proper battery failsafe. Flight 1 (in green) included 108 images, while 98 images were collected during Flight 2 (yellow).
Aerial LiDAR is very effective in collecting data for transmission lines.
Chad Burchette conducts a test run of one of McKim & Creed’s robotic total stations, which can enable us to use one- or two-person crews, rather than two- or three-person crews.