2. Surround the Site
Surrounding the site with ground control is a simple, but often overlooked, step. Usually four to six GCP's will do it. They don't have to be exactly at the outer boundaries of the site, just close. If you drew a line between the outlying GCP's it should box in the site, or be close to it.
The points that surround the site will do most of the heavy lifting in aligning your drone data with the engineer's site plan and your machine control model. If you are flying a long, narrow project like a roadway or levee place two points on each end of the flight plan and at least two or three spaced evenly between them. Add additional points as necessary to bend around a curve.
On the right, the red bullseye's marked "GCP" show you suggested locations ground control locations for an odd shaped factory site. If we drew a line connecting the six GCP's out near the red boundary it would fully contain the site. Don't worry about the GCP's in the middle or the points marked "CK" just yet. We will talk about them in principle three and principle five.
Here is a sewer plant project flown with the Quantum Flight Pack. It took just four GCP's to box in the site.
On the left is a short, straight road project. There are two GCP's tying down each end of the project. These are very important to make sure the drone data does not twist or deviate from the correct orientation. Again, these four end points are the most important GCP's.
If your flight requires multiple flight plans you will need to box in every flight with ground control, then overlap the flight plans over ground control in the sections that run together. This way, it will be easy to merge all of the flights into one continuous data set.
Below is a section of road with two bends. Around the outside of the curve we placed extra control to box in the survey area. Again, play connect-the-dots between the outer GCP's and you will see that it encircles the project. This road is typical of how you would layout ground control for any levee, trail or roadway. It's the same concept for any linear project.