These are a must if you are serious about getting proper NDVI Values.
This package contains 3 ground targets that each have known reflectance curves. The target material has a matte texture with near lambertian reflectance properties, it does not matter where the sun is in the sky for your drone UAV operations. At each flight, take a photo using each camera of the entire open package with the targets facing straight up (no shadows on the entire white target area). Then use these images in the post processing software to calibrate the index image pixel values. This will improve the normalization of your surveys over time and allow you to capture images on days that are not perfectly clear.
The targets are durable, diffuse, easily reproducible (consistent results from batch to batch). They will not fade, peel or change over time, and are highly scratch-resistant. The base substrate is durable processed glass with the coating evaporated in high vacuum.
Using the MAPIR plugin for the Fiji (ImageJ) software you can select the photo of this target taken before your survey, the QR code will be auto-detected and the reflectance value of each target will be calculated and applied to each of your images. The resulting individual images will then be calibrated and you can generate your orthomosaic in the software of your choosing. Using a rastor/index calculator for the desired index (for example NDVI) will properly compute the calibrated indicie values.
//Description interpreted from the manufacturer.