Alos 2 Geo-reference

Yes data is map projected! But what we should do for following error while using Terrain Correction option in Snap software?!
"Source product should not be map projected "

If you want to orthorectify the product with a DEM (Terrain Correction), you need to request the same ALOS acquisition in a lower level format, in this case L1.1

gusortiz has stumpled upon a solution for level 1.5 ALOS data.

I cannot promise that it works for any of you but it’s worth a try:


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Dear mengdahl,

The L1.5 is projected on Ground Range (GRD) but is not map projected.

Since the SNAP performs the Terrain Correction for Sentinel-1 GRD images, it should comprehend the correction for ALOS GRD images.

The L1.1 (SLC) is not available to all scenes.
Many of them are available only as L1.0 (raw) and L1.5 (GRD).

There are actually two kinds. 1.5 and 1.5G. The 1.5G is map projected and cannot be terrain corrected. It should be possible to reproject it. I’ll have to check if current error checking is to restrictive to allow it.
All detected ALOS products from ASF that I’ve seen are 1.5G.
I see some processed from Australia at level 1.5 which are just GRD but it’s missing SRGR coefficients so can’t be terrain corrected either.

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ASF has only ALOS products and not ALOS-2? what about the it?

the SAR-mosaic trick, it works…thanks

Hello everyone,
Does anyone come up with the solution for Terrain Correction of ALOS-2 Data.?

Hello
@lveci any chance this could be change in SNAP so we could terrain correct ALOS2 1.5images although map corrected?
It can be very helpful for plenty of users.

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Regarding map projection, it works… But SAR mosaicking has significantly changed the sigma0 values!
Any idea to solve this?

Change to nearest neighbor resampling

Thanks, with neighbor resampling values also change (a lot)… I can add histograms to this answer, on Monday

I have two ideas:

  • You checked the Normalize option grafik
    This changes the pixels of the rasters according to image statistics so that both contain the same range of values. Uncheck it if you need the absolute backscatter values.
  • The other explanation is that you maybe selected GeoTiff as an output format
    I would recommend to stick to the Beam DIMAP format as long as possible. It is compatible with almost any GIS software and carries all metadata required for the processing of data in SNAP.
    Conversion to GeoTiff causes loss of metadata and brings the risk of changed data type (eg. 16 bit unsigned integer can only carry positive values between 0 and 65,535). This often leads to changed pixel values.
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Thank you very much! I had checked the “Normalize” option.
Now I see some difference in the pixel values, but the differences don’t seem to be significant and the histogram is the same in the original product.

Dear @agustan and all,
I have purchased FBDR1.5GUA ALOS 2 data level 1.5, GEOTIFF and now, I also have terrain correction problem… I was wondering if you have found a solution to process it in SNAp or any other free source software.
Thank you in advance

Dear All, It has been so long time but, that trick in snap I didn’t understand. I have 2 geotiff files HH,HV both in level 1.5 and 2.1. Butwill I use one image only to mosaic? Then says "Geotif has no geo-coding? if I use zip file as an input it runs but the result product is not better than input file… Still shifted…Any help please…?

currently, my only advice is to get the data in Level 1.1, sorry

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@jun_lu Could we check how MapReady handles ALOS level 1.5?

A JIRA ticket ([SITBX-920] - JIRA) has been created to track the problem. We will look into the problem. Thank you