You would need to first coregister the images prior to mosaicking them. You can do this with Image-to-image registration found under the Map ->Registration tools. Were the files recent downloads from the USGS? If not, you might try to find your files again from the USGS website. I think nearly all of the Landsat data is in the newer format and much of it already orthorectified which might provide better registration when mosaicking without having to perform the coregistration.

MarM Many thanks for both your replies. The images are 3 tiles from 1982 recently downloaded from USGS. I have tried to use the Map-Registation tool but can't seem to get it to work. Could you go through the steps I have to follow if you have time? Thanks again S

MariM I think I have managed to work it out, so should be ok for now! Many thanks for your help. S

Hello. I am working with aerial images, from UAV. Before I create the mosaic, I have to fix the misaligned between the six bands of every image. It is the first time that I am using ENVI, so I am a little lost in this... First I exported each band to a single image in order to apply the "registration: image to image", the problem is that the images aren't georeferenced and also don't have tie points. I don't know if this is the way to correct the misaligned or if there is a better way to do it. I would be so grateful if someone could help me with it. Thanks!

It sounds like Image to Image registration is the correct tool to use. It does not require that the images are georeferenced. You should only need to collect tie points between the two images and then run the registration.

Thanks MariM! And how do you collect the tie points in ENVI?

If you follow the tool, you display both images and select coincident points in the images. It is a manual process to do this. You could also try the generate tie points tool but they often need to be adjusted, especially when the images are not georeferenced.

I tried to follow the tool, but It send me this message: "Would you like to select an optional existing tie oints to aid in the auto registration? (Note. non georeferenced input files require at least 3 tie points)" If I say yes, It opens a window to search in my computer for a file with .pts extension. If I say no, It send this message: Non georeferenced input images must have at least 3 tie points in order to run based matching. And close the tool, so I don't have the opportunity to manually select the tie points. I am using envi 5, may I have to do it differently in this version? Thank you very much

It is stating that you must first select at least 3 tie points in order to use the automatic tie point generation, so you must first run Map ->Registration->Select GCPs:Image to Image. After you select at least 3 tie points in the GCP dialog, you can then use Options ->Automatically generate tie points to have ENVI automatically find tie points for you. Be sure to check these points as they often need adjustment with non-georeferenced images, especially if the images have different pixel sizes.

Thank you very much. It worked properly :)

Hello everybody. I have now a new problem related with the previous doubts that I don't know how to solve. I applied the "Registration: Image to image" to correct the misalingment between the bands of an aerial image. With this tool I built the tie points but now I need to build check points in order to assess how good I corrected the misalingment. Does anybody know how to build check points in envi 5? Thank you!