Before starting the survey, calibrate the focus of the DJI Mavic 2 Pro PPK camera and set optimal image processing settings. The following steps are recommended:
- Set the working altitude of the drone. It depends on many factors: the scale of the final orthophoto, lens characteristics, obstacle heights, terrain, etc. The altitude usually ranges from 60 to 120 meters.
- Select the correct frame format. Open the image menu and select the second tab. Select the 3:2 aspect ratio. This format uses the entire area of the camera sensor. Do not use 16:9! Make sure the other parameters in this menu are at their defaults.
- Raise the drone to the working altitude and tilt the gimbal 90 degrees (lowest point). Make sure the focus mode is set to AF. Tap the center of the screen so the camera focuses on the surface. Then change the focus mode to MF – a manual focus scale appears. Do not touch it! The drone camera is now focused for the selected altitude and will not change in the future.
- Now set up the camera. By default all parameters are determined automatically. In that case the brightness and smoothing of the image will change during the flight. This complicates aerial triangulation: tie points will look different on different images. The following
image parameters are recommended for the best quality:
ISO: 100 to 200. Higher values increase image noise and reduce the quality of the orthophoto.
Aperture: 2.8 to 4. Higher values reduce the light, so the image will be darker.
Shutter: 1/1600 to 1/640. Slower values increase blur, faster values reduce the light, so the images will be
darker and less colorful.