ok so i finally took the plunge and did my first real mapping mission, not just messing around, an actual job for a friend who needs a site map for some kind of permit thing. used DroneDeploy for the flight plan on my Mini 4 Pro, flew a double grid at 100m, 80/80 overlap, calm morning no wind. everything looked great in the field

but when i got the orthomosaic back there are these wavy distortions across flat sections, kind of like the ground is rippling. its not terrible but its definitely noticeable and i dont think i can hand this off. did i mess something up in the settings or is this a known thing with the Mini 4 Pro camera. i didnt use any GCPs because i dont have a way to do that yet but i wasnt expecting it to look this bad honestly

yeah thats the bowl effect / doming thing, super common without GCPs especially on flat terrain. the Mini 4 Pro doesnt have RTK so your absolute accuracy is already limited but the waviness on flat ground is usually from the rolling shutter correction not being perfect combined with not enough vertical variation in the imagery for the software to lock in the camera model. a double grid helps but if the terrain is genuinely flat photogrammetry kind of struggles to self-calibrate properly

easiest fix for next time even without a proper GNSS rover is to do an oblique pass around the perimeter, like 30 degree camera angle, it gives the processor more geometry to work with. some people swear by it for flat sites

same thing happend to me on my first few jobs lol. no GCPs on flat ground is rough. if your friend just needs it for a permit thing and the distortion isnt like crazy severe it might still be usable depending on what the permit actually requires, probably worth asking before you reshoot the whole thing