Use of SNAP for sentinel 1A

#21

Hi, yes if you follow the steps described in Section 5 of the S-1 Radiometric Calibration document, https://sentinel.esa.int/documents/247904/685163/S1-Radiometric-Calibration-V1.0.pdf, then your point targets could be used to match the LUT’s values.

However, I suggest you use a different approach - calculate the measured radar cross-section of your point targets (I assume these corner reflectors) and compare with the theoretical radar cross-section of your CRs. Ideally the differences should be small.

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#22

thank you

how to find in which subswath of SLC IW image, does our location falls since subswaths when displayed using snap tool shows same lat long for each subswath
I need guidnace to merge 3 subswaths into single SLC image

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#23

The TOPSAR-Merge module enables you to do that. The images just need to be first debursted (TOPSAR-Deburst).

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#24

It’s not a perfect solution, but you can open the kmz file stored with each product in Google Earth and compare visually

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#25

thank you
Mr. Peter
I tried hard to locate corner reflector in SLC , IW image of Sentinel 1A
Mr. peter, could you assist me to locate corner reflector ( trihedral triangular , 1m) in SLC image
deployment location: lat 12°38’15"N long 77°26’25.72"E
Dates of deployment: 21/07/2017, 2/8/2017, 7/9/2017, 25/10/2017, 18/11/2017, 6/3/2018

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#26

Hi, I have obtained one of your image - from 06/03/2018 - and located your corner reflector. It is at pixel coordinates 10177, 12657 in sub-swath IW2. The cross in the image below shows the predicted position using a terrain height of 660 m. The CR will be at a similar position for your other images.

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#27

Mr Peter, thank you, this will be quite helpful to me

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#28

Hi peter
kindly guide me to find the elevation angle for my location : lat 12°38’15"N long 77°26’25.72"E
for Sentinel 1A pass

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#29

Hi, could you please expand on which angle you are wanting to calculate and why. For example, is it the incident angle at your location from the product annotation. Many thanks.

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#30

Hi peter,
We have plans to deploy dish antenna to monitor S-1A signal strength for which antenna has to be aligned along LOS of the satellite view based on elevation angle. Hence elevation angle is needed for my location: lat 12°38’15"N long 77°26’25.72"E
kindly guide me
thank you

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#31

Hi, I suggest you use the Heavens-Above (HA) web site (https://www.heavens-above.com/) to find the altitude (=elevation) and azimuth for the pass you are interested in. To use HA you will need (I) to set your location (e.g. Devarakaggalahalli) and time e.g. GMT+0hrs, (ii) select a satellite, e.g. S1-A from the ‘Satellite Database’ link down the left hand side of the HA home page. Once you have found Sentinel1-A, select ‘All Passes’ to give a list of when S1-A will be above the horizon from your location. If you click on the date for each pass, you will get more information, including at the bottom, the altitude and azimuth at Maximum Altitude.

For example, there will be an IW acquisition over Devarakaggalahalli with S1-B on 23rd February 2019 between 00:35 and 00:40 UT (see planning at https://sentinel.esa.int/web/sentinel/missions/sentinel-1/observation-scenario/acquisition-segments). As shown in the screenshots below, S1-B will be at an altitude/elevation of 51 deg and azimuth 101 deg at 00:39 UT.


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#32

thank you for the response,

I would like to know if there is any restriction on publishing the contents of S- 1A images in the international journals
2nd query is
can I know Sentinel pass dates for the coming days of March and April month

thank you

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#33

Hi, for your second query, I suggest you look at the planning for S1-A and S1-B available via https://sentinel.esa.int/web/sentinel/missions/sentinel-1/observation-scenario/acquisition-segments. You will need to download the latest kml files and use with Google Earth - as the screenshot below shows, the next acquisition over your site is on 31st March.

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