Checking Stack with RGB image

Hi all,

After several tries and, with different images.
After complete the coregistration step I’m checking the stack as suggested in the ESA InSar tutorial.

And no matter what, changin images, dates, whatever…; I get always the same pattern on the top of te image and some other areas where one of the slave images is dominating.

I think the coherence in this area (plains and really high mountains) is really bad.
Could it be like this or am I doing something wrong?

I selected the images having a look to the Alaska baseline tool. The most perpendicular distance I could get is almost 80 meters


when you compare RGBs you have to make sure that the colors are scaled over the same value range for all three colors in the Color Manipulation tab. Only then you can determine if one image is dominant over the other.
But you are right, the blue pattern is strange, it does not seem to be related to landcover. Have you tested the coherence yet?
It could still be that the phase is not affected by this pattern and that the interferogram is still good in this area.

Hola Andreas,

Thanks for your reply.
Do you mean to this step?

As far as I understund the choerence (as shown in the images) is better between the two images that has a less windows time; and the values are not that good (because a high coherence must has values above 0.6 right?)


the temporal baseline of nearly one year makes it additionally difficult to retrieve good quality. There is too much change between both images. Especially if you want to generate a DEM, a shorter period would be good. But I know it’s hard to find paris with both large perpendicular baselinse and short temporal baselines. Maybe you find a better compromise (e.g. 36 days and 60m)

What matters in the end is the quality of the interferogram. I have seen studies with low coherence which still managed to utilize phase patterns, but it is especially challenging for the derivation of landforms.

Dear Andreas,

Thanks for your reply.

Yes, I’m aware of that. This was a attemp just to try and see If I could get better DEM, since the ones I got before (with less tmp. baseline) did not had the result I was expecting.

I have the feeling that it’s quite difficult to get a good DEM in this area.

Thanks for your help.

I’ll keep trying.