Orthophotos different detail level // referencing two mosaics to each other

[toxicmag]

Dear community,

i created various orthomosaics from one location - having now a big one for the whole area and various spots out of this big area but a lot more detailled.

The big one is georeferenced - the smaller detailed orthos are not (in the small areas not enough GCP were available).

I would like to reference the small ones now afterwards to have them at their correct position in the big ortho.
It would be great to have that done without having to re-process all orthomosaics. Just telling them where they are placed inside the big area and export them again.

QGIS would also be available if that helps....

Thanks in advance.

Alex

[SAV]

Hi toxicmag,

Use the QGIS Georeferencer .

1. Open QGIS and import the big, georeferenced orthomosaic for the whole area

2. Then go to RASTER > GEOREFERENCER and import the first small orthomosaic. Gereference by picking matching points on both the large (georeferenced) orthomosaic and the small one you want to align

3. Repeat for all smaller orthomosaics

DONE.

Regards,
SAV

P.S. Here is some more detailed info on how the georeferencer tool works: http://www.qgistutorials.com/en/docs/georeferencing_basics.html

[toxicmag]

Hey SAV,

thanks for your reply.  
I think it's the easiest way for multiple layers by definition of matching points.

Unfortunately it does not seem to handle tiled orthophotos as a whole.
If i start exporting without having them tiled the client will not be able to handle them.

:/

I will continue to look for solutions...

Greetings

Alex

[SAV]

Hi Alex,

You could first merge the tiles, then georeference the merged raster and then generate tiles again in QGIS. This should work.

Regards,
SAV

[toxicmag]

Hey SAV,

files' origin is Agisoft Photoscan and i'm thinking of doing the reference there in some way, because the quality of the compressed geoTIFF seems to be by far better than the reprocessing in QGIS.


I will check.

Alex

[SAV]

Hi Alex,

If you export your orthophoto at full resolution, it should have the same quality in both QGIS and Photoscan.

If you want to do everything in Photoscan, you could try to use use ALIGN CHUNKS based on MARKERS (which you would need to create first).

Regards,
SAV