The GPS module on board Solo drone is accurate down to around 10 feet. Many Site Scan customers wish to tie their final orthomosaic, mesh, or point cloud to an absolute coordinate system with more accuracy. This is possible with Site Scan and ReCap by setting manual ground control points in the ReCap web app.
6. This menu allows you to add or remove images. If you do not wish to add or remove any images from the processing, click “survey settings.”
7. Survey settings will allow you to set manual ground control points. Select an image from the pane at right that contains one of your ground control points then select an image from the pane at left that contains the same point.
8. Use the reticle to select the same point in both photos. The scroll wheel on your mouse zooms in.
9. Click the pin to add the coordinate that particular ground control point. XYZ is used for local reference frames, ECEF for Earth-Centered, Earth-Fixed, and LLA for lattitude, longitude, and altitude. I almost always use LLA.
10. Repeat steps 7-9 until you have injected all of your ground control points. Typically six ground control points per large Site Scan flight generates a result with several centimeter absolute accuracy. Each ground control point should be identified in 3-4 individual images.
11. Click “settings” and look at the options. Smart cropping automatically crops the model behind the camera and should usually be turned on, smart texture improves the texturing at the expense of processing time, nadir optimization should be turned on for a survey and off for a scan, and formats should be selected as within the Site Scan mobile app. Once you are happy with your selection, click “create.” The project will be resubmitted with the ground control points.
12. The new result should be accurate to within a few centimeters. The images below show a surveyed ground control point superimposed on both an orthomosaic that was generated with and without manual ground control points. Notice that the survey point (green dot) is off by 10 feet or so in the latter and right on target in the former. The target, if not clear, is the cross painted on the road.