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I am looking at Sentinel-1 SAR image downloaded from ESA Copernicus - dhus location around south of Tokyo, Japan. File format is GeoTIFF.

enter image description here

It looks good in QGIS.

enter image description here

However, if I use SAGA,

enter image description here

or SNAP, or OTB-Monteverdi,

enter image description here

the image looks upside down. Maybe "upside-down" is not an appropriate word, as the image lost its ENE-WSW orientation. The image seems simply drawn in XY space swapping lower-left and upper-left as origin.

In addition to QGIS, ArcGIS shows it correctly (according to my friend).

Sentinel-1 images are huge (several GBs) so I cannot test many images, but I reproduced this with randomly selected image in Australia.

Perhaps there are some geotags missed by these software?

Is there a way to modify the image (geotags, to be more specific) to properly read and display it in packages other than QGIS and ArcGIS software?

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The image you use is acquired in ascending mode, that means the satellite moved from southpole to northpole while acquiring it. This information is stored in the metadata but not every software is able to read them correctly. Especially if you directly open the GeoTiff file (which basically stores no metadata at all).

GRD means ground range corrected. That means you have square pixels (the slant range imaging geometry is already corrected), but the image is not geocoded yet. You should apply range doppler terrain correction to the data before you can use it in a GIS.

These tutorials show you how to use Sentinel-1 data in ArcGIS, QGIS and GDAL: https://www.asf.alaska.edu/asf-tutorials/data-recipes/geocode-sentinel1/

I suggest using SNAP (http://step.esa.int/main/download/) which is specialized on radar data and provides best handling of metadata: https://www.asf.alaska.edu/asf-tutorials/data-recipes/correct-sentinel-data/esa-toolbox/ Especially if you open the data in SNAP, don't select the GeoTiff but the manifest file in the folder above. This grants that SNAP adresses all required information.

Another point: If you don't intend to do interferometric analyses, you can download GRD data which is considerably smaller than SLC data.

  • Sorry, but how does this relate to my question? Yes; Some software read S1 SAR correctly while not by others, and it is the center part of my question. The linked tutorials is about reprojection and tells "Download the image and ask experts"... am I missing something? It is appreciated if you could further guide me on this. – Kazuhito May 8 at 4:43
  • Sorry if this wasn't clear. All ascending images look "upside down", while all descending images are "correct". This is why you don't open the tif file but the data including all its metadata so you can reproject it to have it oriented correctly. – AndyB May 8 at 8:21
  • Believe me, QGIS displays images in correct position / orientation without the help from the metadata, regardless image was taken descending or ascending. There has to be something in GeoTIFF. – Kazuhito May 8 at 9:47

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