Preparing to capture an image of your CRP
Taking an image of the Calibrated Reflectance Panel is a very important part of data collection, as these images help calibrate your data based on the day's lighting conditions.
We recommend taking a capture of the CRP immediately before and after each flight, with the panel flat on the ground in an open area from about 1m in height. This is best done by holding the camera/drone with the sun to your back such that the sun is hitting the panel but light isn't reflected onto the panel from your clothes or from any surrounding objects. Normally this can be achieved by standing directly in front of the CRP with the sun hitting your back, and take one big step to either side so the panel has no shadows being cast over the grey material.
How to capture an image of your CRP
To take a capture with the camera, there are several options:
1) Pushing the trigger/power button of the camera (near the status LED)
2) Pushing the button located on the DLS2. Be careful not to block any of the sensors on the DLS2 while doing this.
3) The capture button on the camera's web interface (this immediately triggers a capture). How do I connect to MicaSense sensors?
4) The QR mode button (this searches for the QR code and automatically triggers a capture when found). Read more about QR mode here.
You can confirm a capture was successful by seeing the camera and DLS2 status lights flash BLUE. If you're using the web interface you will also see a jpeg preview of each band, which helps to confirm the panel was aligned within the frame of the image.
When capturing images of the panel under fully cloudy skies, take care not to block the incident light from the clouds from showing up on the panel. In cloudy conditions, the aircraft may cast a shadow on the panel but the shadow may not be apparent.
Imaging the panel using the camera by itself outside of the aircraft may be required in the aircraft is very large and blocks a significant portion of the light.
When deciding which panel image to use for processing in Pix4D or other third-party image processing software, choose the panel image taken at a time that best represents the average illumination of the flight. For example, if it was sunny when you took the first panel image but then clouds moved in and covered the sky for the majority of the flight, you would want to ensure you use a panel image that was taken under the cloudy sky.
The look of your CRP may vary depending on when it was manufactured (iterations are distinguished via the serial number, which start with the letters "RP")
Examples of CRP made by MicaSense:
Panel Reflectance Values
While most panels have the 'albedo' values printed by the QR codes, you may want the full list of reflectance values across the entire measured spectrum (typically 250nm to 950nm wavelength). To download your panel's reflectance values, please have your panel's serial number ready and visit micasense.com/prv.
Taking care of your panel
Despite its looks, the CRP should be considered delicate scientific instrument, and requires proper care to prevent the reflectance surface to be compromised. The instructions to take care of your CRP varies depending on the serial number. We've made an article dedicated to this here: Calibrated Reflectance Panel Care Instructions