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. Below you find suggested values.
| ASL Alt m | GP8MP3+ (cm) | GP12MP3+ (cm) | DJI P3 4K (cm) | MAPIR 2 (cm) |
|---|---|---|---|---|
| 15 | 1.08 | 0.9 | 0.63 | 0.56 |
| 30 | 2.16 | 1.8 | 1.27 | 1.03 |
| 75 | 5.4 | 4.5 | 3.2 | 2.53 |
| 100 | 7.2 | 6.0 | 4.25 | 3.38 |
Ground Resolution of typical cameras
Depending on the product and manufactor of the cameras you have to deal with different speeds. NOTE: Only the speed that can be continously achieved is taken into account. Currently a picture rate of 2 sconds is the maximum in speed.
It is strongly recommended that you use (if available) an autonoumous camera timer (time lapse) for controlling the pictures interval.
On average the fasted SD Cards will be able to achieve an average speed of about 2 seconds/JPEG (Raw + JPEG 3.5 seconds) image. As a result taking pictures every 2 seconds will be a sporty attempt. The Flight speed recommodations are meeting this needs. Let us assume you fly a task with the field of view (FOV) of the DJI 4K camera at 35 meters above ground level (AGL). To derive the maximum flight distance from picture to picture in meter for the given overlap you have to calculate:
\(FOV*agl*(1-overlap) = 1,71*35*0,2 = 12 m\)
If you can take a picture every 2 seconds your max speed is: \(12 m / 2 s = 6 m/s\)
For JPG pictures: \(0,15 * agl (RAW; 0,07 * agl)\) For a 100 meter AGL flight you should set the speed to a maximum of: \(0,15 * 100 = 15 m/s (54 km/h)\) For a flight of 35m agl this is will be roughly 5,25 m/s ## DEM/DSM Data 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.
Actually you also should check the weather. Forget about flying with wind speed above 4 Beaufort - the UAV is not a falcon.