How can I use Tie point in SNAP to see the correlation between two images?
tie point grids contain information about the geocoding of the images. I’m not sure if this is what you seach for.
If you want to investigate the correlation between two images, you have to bring them into one product, for example using the collocation tool. Afterwards, you can use the scatter plot 
to see how pixel values of both images
Thank you for replying.
My issue is that I have two sets of images one sar and optical each. I have collocated them. Now I want to see the correlation between the two sets of images. Compare if the pixels in one set correspond identically to the same location in the other set.
Scatter plot is not helpful here since I am unable to compare same band (eg. B1) of both sets.
Scatter point only lets me compare the bands within one collocated dataset.
kindly guide.
attached is the issue I face when I zoom in to the two sets of colocated images and find there is half a pixel mismatch between the two sets thus I would like to find the correlation between one band in both the data sets.
actually, this is what scatter plot allows you to do.
After collocation you have B1_master and B1_slave and can plot them on a cartesian coordinate system.