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How to georectify updated maps of an area to exactly match the first map?


I am using a drone to shoot maps of a golf course and I update the maps every week.

Because the GPS system in the drone tags the images, it automatically produces georeferenced imagery that is stitched into an orthomosaic TIF map. However, it's not an RTK system and I'm not using GCP's, so the accuracy varies between maps, up to about 90ft. I need to force all of the maps to overlay exactly on top of one another - the actual accuracy of the maps on the surface of the planet isn't as important to me as all of the maps exactly matching. 

If my first explanation isn't making sense, I essentially need to pick several points throughout the original TIF map to reference and force a shift onto subsequent maps, making them line up perfectly. I don't know if GM will automatically scale/shift the data to force fit the points or if it will simply use three or four points to more accurately line the maps up.

It was recommended to me to use QGIS to do this task, but since our company has a GM license, I'd like to use it instead. I don't quite know how to phrase my searches when looking for this specific topic (since I don't know if georectify is the correct term), so if my question has already been answered in another thread, I would really appreciate someone commenting a link to the appropriate discussion.

Thanks for your help!


  • kfroesekfroese Geotechnical Engineer Posts: 186Trusted User
    I am intending to do a similar thing with annual flights over sites affected by slow-moving landslides. This is the first year I've flown some of them so I haven't had to work it out yet (not sure if I'll be able to fly them again as my drone got dive-bombed by swallows during the flight - nearly crashed it!). My intent is to use common reference points to establish relative ground control points (GCPs). I put down some small targets that I've left in place. I'll use this year's flights to establish coordinates for them (which will be slightly off in the global sense as I'm not using RTK either) and then I'll use those coordinates GCPs for subsequent flights. I'm hopeful that will allow me to relatively reference sets of photos to each other. It seems like you could do something similar using hard targets from the first flight to set GCP. Perhaps the holes in each green? They shouldn't move between flights so could be used as references.
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