05-02-2018 06:31 AM
I've got some Pleiades images covering 150x75 km approximately, we can name this area AOI. This site is divided on several smaller area (30x20 km approx.) and for each smaller area I've got a triplet (so, 3 images), we can name these area SAOI. I can build Orthophotography from each Pleiades images with Erdas Images using the Orthorectification without GCP tool. But, when I build 3 orthophotography of the 3 Pleiades images covering a same SAOI, the Orthorectified images aren't georeferenced well (a same object on the 3 images is approximately shifted from 10 m) and it's the same with two different SAOI, there is some shifts between the two SAOI (if we take a road, for example, on the 2 images, the road is shifted at the intersection of the two SAOI).
Is someone already face this issue and get a solution?
Thank's a lot in advance !
05-02-2018 08:25 AM - edited 05-02-2018 09:09 AM
Before trying anything else, please check the following:
If all those are correct, but you are still getting spatial inaccuracies, then it may well be that the source geometric model information provided with the data is not spatially accurate (to the degree you desire). In this case you will need to measure Ground Control to tie the model down more accurately. Frequently this can be done with just a single GCP, but the number required will vary depending on the nature of the data and its inherent inaccuracies (and the local terrain and relative accuracy of your elevation source). For example, if you have two scenes of the same area taken from different viewing angles and your DEM doesn't adequately model the terrain displacement effects, the orthorectified images are going to have relative positional errors.
If correcting multiple images in an area you may also wish to consider using IMAGINE Photogrammetry to perform a block bundle adjustment to get results which overlap with a high degree of accuracy.
For multi-date imagery which overlaps in a "SAOI" you may also wish to try IMAGINE Autosync (which is part of the IMAGINE Expansion Pack product) if the above steps aren't providing the required level of accuracy.
Hope this helps,