It is most important that you setup your survey with an appropriate overlap for reliable stitching results. If the overlap is too small or vice versa you fly too fast you will get poor or no results. Same is with the flight altitude and the camera settings.
Front Overlap 80%, Side Overlap 75%
Below you find values for ground resolution typical camera.
| AGL | GP8MP3+ | GP12MP3+ | DJIP3-4K | MAPIR-2 | DJI-Mini-2 |
|---|---|---|---|---|---|
| 15m | 1.08 | 0.9 | 0.63 | 0.56 | 0.8 |
| 30m | 2.16 | 1.8 | 1.27 | 1.03 | 1.6 |
| 75m | 5.4 | 4.5 | 3.2 | 2.53 | 3.9 |
| 100m | 7.2 | 6.0 | 4.25 | 3.38 | 5.2 |
Ground Resolution of typical cameras in cm with respect to the above surface level.
Depending on the product and manufacturer of the cameras you have to deal with different flight speeds. NOTE: Only the speed that can be continuously achieved is taken into account. Currently a picture rate of 2 seconds is the maximum in speed.
On average both SD Cards and cameras will be able to achieve an average speed of about 2 seconds/image. As a result taking pictures at least every 2 seconds is a bit challenging. So roughly you can estimate the flight altitude from the ground resolution and the maximum flight speed according to this from the following rule of thumb:
\[maxSpeed~(km/h) = (0.2 * AGL)*3.6\]For a 100 meter AGL flight you should set the speed to a maximum of:
\[0.2 * 100 = 20~(m/s) = 72~(km/h)\]For a flight of 40 m AGL this is will be roughly: \(5.25~(m/s) = 28.8~(km/h)\)
Please note that maximum speed is usually not the best choice.
If you fly in an wide open flat area you do not need additional data. But if you fly in middle range mountains, forests or similar complex structures you will need a digtal surface model (DSM/DEM) for retrieving an optimal and safe flight path. Depending on the Software you have to take care of this issue manually.
As simple this seems it is full of pitfalls. Therefore we would like to provide some checklist: