When officials in Sarpy County, Nebraska began looking at ways to connect additional traffic from a new bridge built on Highway 34 over the Missouri River they realized it would require a lot of data for planning and design. Platteview Road would be a major connector of the most southern continuous east-west route expanding this two-lane roadway from the 1960s to a four-lane highway.
This is a guest post by Cyn Rene’ Whitfield at the Trekk Design Group.
This spring, TREKK used the combination of survey tools and the varying aspects of terrestrial mobile LiDAR, UAV LiDAR and UAV photogrammetry to establish the base mapping for this more than $100 million transportation project near Omaha. Within two days, we acquired 8.33 miles of two-lane highway, 2.71 miles of cross streets and 700 acres of farmland areas outside the current right-of-way.
Having a variety of survey-grade tools is just part of data acquisition. Understanding the best way to use them and which tool to use while maintaining a common workflow can be just as important.
Terrestrial Mobile LiDAR collects up to a million points per second while traveling on the roadway at posted highway speed. TREKK used this technology to acquire data along the entire Olatteview Road corridor and side streets. Driving each lane on the roadway allowed 100% coverage of the pavement surface to an accuracy of plus or minus 0.05’. In addition, terrestrial mobile LiDAR covered much of the right-of-way outside of the pavement surface.
UAV LiDAR gathers a wider swath of data in less time. It can generate 100,000 points per second with up to five returns per laser pulse, allowing greater penetration through vegetation. UAV LiDAR was flown over the entire project to supplement terrestrial mobile LiDAR and UAV photogrammetry. Because of the high nadir vantage point UAV LiDAR data was used to fill in occluded areas of roadway slopes like ditches and vegetation. The systems navigation can achieve relative accuracies of plus or minus 0.15’
UAV Photogrammetry maps open area corridors providing high definition digital orthographic photos and colorized 3D points at ½ inch intervals. We acquired UAV photogrammetry over the entire project area to create a rich, colorized 3D point cloud. Much of the DTM in the 700 acres lying outside of the current right-of-way was created from this point cloud to an accuracy of 0.05”.
“It’s not redundant data and it’s not overkill or over collecting,” said TREKK’s LiDAR/Survey Manager Michael Frecks. “Each tool has unique aspects that provide for a complete and accurate survey. All three data sets were compared to survey control using RMS QA/QC checks and heat maps. Each tool provided unique advantages during QA/QC cross checks built into the final deliverable.”
The powerful combination of these technologies; terrestrial mobile LiDAR, UAV LiDAR and UAV photogrammetry provided a complete base mapping of visible features on this project. Independent processing unique to each tool also provided an additional level of QA/QC. TREKK’s experience on combining different tools and platforms to collect rich point cloud data have been powerful on many projects. Let us put our tools to work on your next project.
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