# A pair in high latitute

Dear friends
I wan to work on one island (Hailuoto, Finland) and do interferometry, it is located between two sequences acquisitions like a overlaping pictures (I think fortunately). You can see two pictures (two sequences acquisitions).
Master: 20150302T044810_20150302T044838
Slave: 20150302T044835_ 20150302T044902
Can we make interferometry with both - maybe i can extract it from two pictures -or should we have two repeat pass pictures (I mean 12 days differences for Sentinel1, a pair, although I think the temporal difference between two pair should be less than 1 day for my island )?
As I see in the ´Sentinel-1 User Handbook´ , the revisit frequency is less than one day in high latitudes. How can I find one pair in high latitude by less than one day?
Cheers,
Marjan

What is the objects of your Interferometry?

and do these two images meet up all the initial requirements of InSAR?

Some hints the track of both image, the temporal baseline, perpendicular baseline

My object is ice displacement.
I think the perpendicular baseline is when you are using two satellite or one satellite with simultaneus baseline but I am using Sentinel1 satellite. How can I find its perpendicular baseline? Has it any perpendicular baseline?

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in snap

A pair must completely cover each other. I do not know why I can not find a pair in high latitude by less that 1 or 2 days differences in temporal baseline. As I know when somebody is working on high latitute, then he/she must find a pair by less than 12 days differences in temporal baseline. Am I right?
My area is Hailuoto island, Finland.

Those two products in the initial post are from the same datatake, ie they were acquired one after the other as the satellite flew overhead. The acquisition times indicate so.
The consequence is that the two products don’t overlap. The image footprint on the left in your screenshots is just a rough approximation of where the image is.

If you go to high latitudes you can indeed find places that are observed more than once per day, but not in repeat tracks (the relative orbit number of the two products will be different). If you need repeat tracks you have to wait 12 days (S1A or S1B alone) or 6 days (S1A+S1B) whether you are in the pole or in the equator.

please do not cross-post the same questions over various topics.

Yes. Thank you. It means, if I want to do interferometry, I must have
repeat tracks?

Depends a bit on your aim.
To my experience, only single-track data worked for me in SNAP so far.

Interferometry with the baseline orthogonal to the velocity vector is sometimes referred to as cross-track interferometry(CTI), and is used for measuring height variations. Interferometry with the baseline aligned with the velocity vector is referred to as along-track interferometry (ATI), and is used for measuring temporal changes in the SAR scene, e.g. velocity field mapping of waves, glaciers, and so forth. ATI systems typically place two apertures along the side of the platform, one fore and one aft. If the data is obtained by two-pass operation along the same flight path, it is called repeat-pass interferometry (RTI).

Source: Richards: http://users.ece.gatech.edu/mrichard/AESS%20IFSAR%20Tutorial.pdf