We recently performed a drone LIDAR Mapping experiment with a GeoCue True View 410 client. The test was to see how well the True View 410 Imagery/LIDAR sensor (3D Imaging System, 3DIS) could perform when mapping relatively steep terrain.
We selected a site about 1 hour away from our GeoCue office located in the foothills of the Appalachian Mountains in northeastern Alabama. The site, referred to as the Rock Farm (you can guess the reason for this name!), is depicted in Figure 1. The grid spacing in the planimetric view is 10 m x 10 m and 5 m x 5 m in the profile view. The approximate LIDAR/imagery coverage area is 0.64 km2 (160 acres). The project distance along the example profile line shown in white in Figure 1 is about 1,100 m (1.1 km). The rise over this segment is 195 m. This gives an average slope of 18%.
Figure 1 – The Rock Farm
We normally recommend a flying height of 75 m. We performed the 75 m test with excellent results and then the client wanted to experiment with a 100 m flight. We used Litchi (from VC Technology Ltd) mission planning software and flight management system for the 3D flight. The Litchi software uses an elevation database to model the terrain for automatic 3D mission planning (note that by year-end, we should have 3D mission planning added to our True View Evo processing software)
We consider the useful maximum range of the True View 410 to be around 75 m. The LIDAR sensor we use is rated to 200 m, but we like to give you very useful, practical specifications. We were very pleased with the 100 m range results for this type project. We observed densities in the ground class in treed areas ranging from 125 pts/m2 down to 25 pts/m2. The conditions are leaf-off. Thus you can see that we had excellent results with this project. The 75 m recommendation comes in to play for very low reflectivity surfaces such as pavements.
We used our True View Evo automatic ground classification to separate the ground points from all other points (in this project, mostly trees). Running the ground classifier required 2 minutes and 4 seconds. The results, even with no manual cleanup, were sufficient to support a gridded elevation file or topographic contours. As an example, we used True View Evo to produce a set of 1m contours of the site using the ground surface computed from the automatic ground classification algorithm (see Figure 2).
Figure 2 – 1 m Topographic Contours of the Rock Farm
I think it is quite remarkable to fly a site such as this in the morning and deliver derivative products in the afternoon. The Return on Investment of the technology really is a step jump as opposed to an incremental improvement. With subscription plans available for the True View 410, testing the waters is easy and very low risk. If you feel that the True View 410 system would fit your needs, feel free to contact below or give us a call at 256-461-8289.