orthorectification error - image DEM not overlap

Prev Go to previous topic

Go to next topic

Last Post 11 Oct 2018 09:30 AM by Patricio Romero

3 Replies

Sort:


You are not authorized to post a reply.

Author

Messages

anon

New Member

Posts:23

22 Mar 2013 09:57 AM
Hello, I'm trying to orthorectify a QB image, using a DEM. Both images cover roughly the same area, with the DEM having a slightly larger extent than the QB image. I can link the viewers or geographically link them and the areas correspond (see link here: https://dl.dropbox.com/u/42285242/_ENVI_orthorectification_overlap_issues.jpg). The DSM on the right side is just there for reference and corresponds to the DEM 1:1. However when I try the orthorectification (Map-Orthorectification-Quickbird-Orthorectify Quickbird), input the images and try to execute the tool, I get the following error: "Problem: Image and DEM do not overlap." Obviously the images do overlap, so I'm wondering why I'm getting this errror. I suspect it has something to do with the image headers' offset settings (also shown in link) but not sure how I'd go about fixing that. The datums are different too (Nad83 vs. WGS84), but I'd think ENVI can handle that on the fly. Or is there something else I'm missing? Mike

MariM

Veteran Member

Posts:2396
Veteran Member

22 Mar 2013 12:31 PM
Typically you would get this error if the DEM does not completely encompass the image area you want to orthorectify. You mention the offsets but those should only affect the pixel linking and not the orthorectification (I wouldn't think). You could remove them (set them to 1) and they should not affect the geographic linking at all. I would be sure to look around the entire edge of the image and make sure the DEM covers that area, preferably with some buffer area beyond the image extents. I would also turn on the RPC positioning in the ENVI Header and check the geographic link around the borders. Orthorectification is going to use the RPC information and not the map information already present in the image. If the RPC positining is significantly different than the map information currently present in the file, you could have areas that are not covered by the DEM. If you still see good DEM coverage, I would contact Technical Support directly.

Deleted User

New Member

Posts:23

22 Mar 2013 01:12 PM
Hi MariM, Thanks for the quick reply. I tried your suggestions to turn on the RPC positioning in the header. I also made sure the DEM entirely encompasses the QB image. I actually had subset the QB image to ensure that's the case, which I verified by checking everything by geographically linking the two images. However, I got still the same error. I guess I'll contact tech support with the issue. Mike

Patricio Romero

New Member

Posts:4

11 Oct 2018 09:30 AM
Hi Mari and Mike. Let me tell you that I have the same problem. In fact, Mari tried to help me. I have tried with a SPOT 5 Level 2A and I can get de RPC. I saw that the projection changed when I run by de GCP point. I have a similar dem and other larger. However, the results is the same "image and dem do not overlap" and I can not get the orthorectificated images. Could you resolved it? I will appreciate any information. Patricio

You are not authorized to post a reply.