I am surveying an area of about 2 acres with wheat sown in it. I am using DJI Matrice Pro 600 with Micasense Altum sensor. I am using DJI pilot for flying the mission with same parameters and the camera parameters are also same.
I did two flights on same day, 15 min apart with same settings and processed them in Pix4D with Ag Multispectral template. When I compare NDVI maps of both flights, I see a slight variation in pixel size. Although in pilot app I get GSD = 1.73cm/pixel while processed NDVI maps have pixel size of 1.716cm and 1.697cm.
Now, I just want to know if this is normal or not? I don't have accurate GNSS to get coordinates of GCPs but I used 1st flight's GCPs as Manual Tie Points (MTP) and exported them to be used in 2nd flight processing.
Am I doing everything OK? and why is there variation in pixel size and why don't both maps align as I am using same points for processing both flights.