This year we have started commercial ortho-imaging services and did our first job for our client in that field. Our first order was quite big - to scan and create a geo-referenced orthophoto from about 12 km2 / 3000 acre area for our local municipality.
We performed the project within two long (10-12 hr) days in May & June in the endless light of Finnish summer, here near the Polar Circle, with one Mavic 2 Pro and about 15 batteries per day. We were flying from 150 m AGL, EVLOS, with all the necessary permissions from local Air Navigation Services.
I thought that flying the whole area in a one map is a no-no (I was afraid of that something goes wrong and we need to re-fly the whole thing), so I split the are to 6 sub-maps (about 2 km2 / 500 acre each) with some overlapping around the borders of each map.
Our client provided us 16 GCPs for the whole area, but unfortunately only 3 of them fell under each sub-map.
DroneDeploy did process the georeferencing with just 3 GCPs, despite the guide telling to have a minimum of 4.
All seemed to go good, but now in the autumn, when our client started to use the maps, they found that the georeferencing is way off - something like 5 meters in the edges of the maps, rendering the ortho-images unusable in their GIS application.
Another problem they were not happy about, was that the transitions between each ortho-image from the sub-maps we’ve shot individually, were quite too visible, as there were (of course) different lighting scenario when shooting each map, due to different time of day when shooting them.
Our client would want to have the borders of each ortho-image “mosaiqued” so that the borders would not be straight lines, but instead maybe softer ones, or following some terrain details like roads or building edges, thus making them less distracting when viewing the whole 12 km2 area.
I have just asked tips from DD support what I could do at this point, but I thought to share this issue also here in the forum, to hear if you guys have suggestions how these kind of huge (3000+ acre) areas would be best captured and georeferenced – in future projects, should I shoot one huge map with several thousand photos, or is there some way to combine smaller maps together to a more seamless, big, (accurately) georeferenced OrthoTIFF?
Thank you a lot in advance for your thoughts!