I have downloaded product of S1 “S1A_IW_SLC__1SDV_20190123T013358_20190123T013425_025598_02D753_AEA6”, how can I confirm from product name that whether this product is ascending or decensing and also VV or VH?

Hi, From the filename itself, you cannot tell if the product is ascending or descending. The DV after the …SLC__1S… in the filename indicates the product is dual polarisation with combinations VV and VH (i.e. the product contains two sets of data, one for VV polarisation and the other VH polarisation). DH is dual H polarisation - HH and HV.

One way to check the ascending/descending is open the map-overlay.kml file in the review folder of the product in Google Earth. If the north-west corner has the highest latitude, then this is an ascending pass - if the north-east corner has the highest latitude, then it is descending.

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The scene looks like this

So this is a descending scene where near range is to the left, far range is to the right and azimuth time increases from top to bottom. Peter.

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Thank you. is there any difference if we take two images of ascending and two descending? can we take one ascnding and one descending?i.e master slave?

It depends on what your application is. If you want to perform interferometry than you will not only need to use the same pass type (asc or dec) but also the same relative orbit. This is to ensure that the same region on the ground is imaged for the master and slave.

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Thank you so much.

can you make it more clear

Maybe you can specifiy what exactly your question refers to. If we understand your problem, we can try to help.

Thank you for your prompt response my question was what exactly ascending or descending mean and is there any criteria to select an image in ascending or descending direction additionally I am trying to pre-process Sentinel-1 image but it doesn’t finish the processes even for radiometric calibration can help me with that, please?

ascending and descending are simply the direction of movement of the sensor. Acending is from southpole to northpole and descending vice versa. As Sentinel-1 is right-looking this simply determines from which side the image is acquired. This makes a difference if you have strong topography in your image with foresthortening, layover and shadow effects.


About the preprocessing: Please have a look in this topic and describe your problem there (what data you are using, what you applied and what error message you get): Radiometric & Geometric Correction Workflow