Radiometric Calibration target is a White balance card with known Reflectance / Albedo Value for each of the multispectral bands. It is used as a reference panel for estimating reflectance of a given surface. Usually, the Radiometric Calibration target is provided as a Grey color box by the multispectral sensor’s manufacturer.
To capture Radiometric target images with the help of a Lancaster drone, follow these steps.
Note: You should capture RadiometricCalibration images before and even after the survey.
1. Open the Calibration target (Grey Color box) and place it on the ground (Figure 1).
Note: Make sure that the Calibration target is placed on a flat surface.
Figure 1: Calibration target placed on the ground
2. Turn On the drone camera. The Lancaster drone will automatically detect the camera type (Figure 2).
Figure 2: Lancaster detecting the camera type (RedEdge 3)
3. Once the drone detects the camera, the OLED screen displays following instructional message – Please point the camera at the calibration target to capture the calibration image (Figure 3).
Press OK (the Green checkmark button) to continue.
Figure 3: Screen displaying instruction
4. Now, position yourself in a way that your back faces the sun, then place the camera (thus the drone) directly 1 or 2 meters above the Calibration target such that the sun rays directly hit the Calibration target without creating any shadows on it (Figure 4 and Figure 5).
Figure 4: Correct posture for capturing radiometric calibration images
Figure 5: Calibration target covered with shadows due to incorrect posture (Incorrect practice)
5. Once you have set yourself in the correct position, click five images of the Calibration target by pressing OK button five times (Figure 6).
Figure 6: Clicking Radiometric calibration images
This concludes the procedure of capturing Calibration images. You can continue capturing your survey. Do not forget to repeat the Calibration process once the survey is completed.
To know how to upload the captured Radiometric images, refer “How to Upload Radiometric Calibration images”.