Repeat-pass interferometry

Dear all,
There are basically three different concepts of SAR interferometry: 1) single-pass along-track interferometry, 2) single-pass across-track interferometry, and 3) repeat-pass interferometry.

The single-pass concepts illuminate the surface simultaneously in time with two spatially separated antennas. For the along-track case, the antennas are separated in the along-track direction. Systems using the along-track InSAR technique are mainly airborne, but the technique has also been demonstrated on the Space Shuttle. The along-track configuration is mainly used to study ocean surface currents and wave

In the across-track configuration, the antennas are separated in the across-track direction. Such systems are operated onboard aircrafts and has also been flown on a Space Shuttle mission. The single-pass across-track mode is mainly used for digital elevation mapping. As an example, the NASA Shuttle Radar Topography Mission (SRTM) in 1999 was able to produce a global digital topography dataset of the Earth’s surface covering all land areas between 60 ◦ north and 54 ◦ south latitude.

The last concept, and the one relevant for most satellite systems, is the repeat-pass interferometry configuration. This mode utilizes the fact that the repeat cycle of the satellite is not perfect, resulting in an across-track shift of orbits of typically a few hundred metres. This means that the repeat-pass data are acquired at different times compared with the single-pass modes. This provides the possibility to study phenomena related to surface changes such as e.g. ice dynamics, land deformation, and land cover changes occurring between the satellite acquisitions.

What is differences between topography map and land deformation?
In my understanding: topography map is included hight information but land deformation is included horizontal and vertical displacement.
Am I right?
What is difference between topography and vertical displacement?

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In displacement map you have to exlude known topography, using known dem model (Srtm e.c
t). Topography map you have both.

How we can delete topography part by SNAP and we can see displacement?
can ‘Topographic Phase Removal’ do this?

Yes, it should do. It use SRTM mainly other dems are problematic (watch forum topics) :slight_smile:

Thanks but I am using GETASSE30. How about it?:grin:

if it works it works. other dems are mainly technical problems.

As far as I know, the two seperate antennas onboard SRTM work at along-track modes, which are C-band on the shuttle payload bay and X-band on the 60m mast which extends from the shuttle. As for across-track configuration, in my opinion, a good example is the twins satellite, TanDEM-X and TerraSAR-X, which share the same orbit and has a close formation distance of several hundred meters. The DEM produced by the twin is the most accurate up to date, which has a vertical accuracy of 2 meters and horizontal accuracy of 15 meters or so.
Please correct me if I was wrong. Thanks in advance :smiley: