NE South Dakota Clark, SD | LIDAR and RTK both have advantages and weakness. I use LIDAR for tile design all the time. As long as you understand the shortfalls it is awesome. Here are the problems with LIDAR. It does not penetrate water or dense vegetation. If the field happened to have a lot of standing water or was in CRP at the time, it is not great. Any cattails or similar vegetation in ditches or wetlands, will be inaccurate. If any major changes have been made to a field ie: leveling or major ditching will make the LIDAR no longer reliable. The best parts of LIDAR are .75 to 1 meter resolution. You can look at the whole area vs just where you can drive to collect RTK. After all water does not care who's side of the property line it is on, it wants to flow down hill. If you look at a small area vs large area, the flow direction my be different.
The drawbacks to RTK are distance to base that can effect accuracy. For best data collection be within 2 miles of the base. However 4-6 miles is acceptable. Probably the biggest drawback to RTK is that most people are not going to have the patience to drive at 3-6 ft spacings.
As Goosepilot said, for zone work, 3-5 meter resolution is plenty good. I have used SRTM DEM elevation data for zones. It is 10 to 30 meter resolution. Most of the farm ground in the US is available at 10 meter.
So I was having a hard time getting to sleep last night, so i decided to put this to the test. I have seen it done before, but had not done it myself, with data I had collected myself. So here is the test. LIDAR was flown 10/31/2011. RTK Was collected 11/10/2012. A couple things that might screw the results slightly. When the LIDAR was flown, the field had been in pasture for about 20 years, the sheep keep it eaten down pretty good, but not perfectly even. When I drove to collect RTK data @ 50 ft spacing, it had been disked with a Wishek disk and was very rough. I had to go very slow to not wreck myself and my pickup. In the attached pics is the results. I also had flown it with an Ag Eagle drone, so I compared that to the LIDAR as well. Of the 32 acres on the field comparing LIDAR to RTK 20.2 acres was within +/- .25 feet. 10.9 acres was +/- .25 - .56 ft and the last .3 acres was +/- .56 - .84 feet. If you look at the comparison map, you will see that a lot of the areas that varied, were in east to west streaks. This is the direction I drove the field, so I feel that has some bearing on the results. I did have to adjust the LIDAR to RTK by aprox. 31 ft. This is common due to LIDAR using surveyed benchmarks and the RTK was not.
The Ag Eagle to LIDAR was not near as good. 18.4 acres was - 4.13-5.31 ft/ This was the large flat area of the field. It definitely shows relative elevation change, but accuracy was not great.
Edited by gpsdude 4/29/2016 10:27
 (Elevation RTK Points.jpg)
 (Elevation RTK Triangulated.jpg)
 (Elevation LIDAR 1 M.jpg)
 (RTK LIDAR Difference.jpg)
 (Elevation Ag Eagle.jpg)
 (AG Eagle LIDAR Difference.jpg)
 (Elevation SRTM DEM.jpg)
Attachments
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 Elevation RTK Points.jpg (115KB - 156 downloads)
Elevation RTK Triangulated.jpg (84KB - 167 downloads)
Elevation LIDAR 1 M.jpg (89KB - 163 downloads)
RTK LIDAR Difference.jpg (92KB - 148 downloads)
Elevation Ag Eagle.jpg (88KB - 163 downloads)
AG Eagle LIDAR Difference.jpg (72KB - 154 downloads)
Elevation SRTM DEM.jpg (80KB - 154 downloads)
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Lidar vs. RTK map
