Resolution of TanDEM-X data

Dear friends

I have a question about spatial resolution of TanDEM-X data. Actually, I opened a TanDEM-X data and I measure its pixel in two different locations;

One in center and it was: 3.…meters

One in side and it was: 2.6…meters

Then I went to metadata and I saw these numbers:

Range-spacing: 0.90940……meters


So, now I have some questions:

  • Why when I measure pixels in different location, then I have different amounts?which one is better to report?
  • Why range-spacing and azimuth spacing are different than something I measure by ruler in SNAP?
  • Actually, when I downloaded data, it has a overview that they wrote its resolution 3.134243488405855meters. so how this is possible?

Would you please guide me?