Opened 10 years ago
Closed 10 years ago
#3709 closed defect (fixed)
Georeference problem with Envisat Images
Reported by: | timatkinson | Owned by: | chaitanya |
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Priority: | high | Milestone: | 1.8.1 |
Component: | GDAL_Raster | Version: | unspecified |
Severity: | critical | Keywords: | Envisat GeoReference |
Cc: | warmerdam, Even Rouault, antonio |
Description
Gdal 1.6.2 (as featured in Fedora 13) and gdal 1.7.2 (as featured in Ubuntu 10.4) both have a problem with Georeference of Envisat Images
It appears they are reading both the Geolocation grid ADS (correct) and the Doppler Centroid Grid (incorrect) as GCPs.
The numbers in the grids are similar but actually different and hence you get two sets of ground coordinates per one GCP Line,Column
Run the command line below (*.N1 any envisat file will do)
gdalinfo *.N1 | grep \(0.5,0.5\) and you'll instantly see the problem
Change History (10)
comment:1 Changed 10 years ago by
Cc: | chaitanya added |
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Component: | default → GDAL_Raster |
comment:2 Changed 10 years ago by
Tim,
Can you provide some sample data? You can email it to me (chaitanya.ch * gmail.com) if you want it to be confidential.
comment:3 Changed 10 years ago by
Cc: | warmerdam added; chaitanya removed |
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Owner: | changed from warmerdam to chaitanya |
Status: | new → assigned |
I was able to reproduce the problem with a sample dataset from Anders Berg. I'm working on this.
comment:4 Changed 10 years ago by
Severity: | normal → critical |
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For Envisat ASAR, the mistake is that the parameter "line_num" of Geolocation Grid is used as the Y-coordinate (tested with gdalinfo v1.7). In the ESA documentation for ASAR Level 1 products, there is a warning that "line_num" is the line number relative to the "granule within the slice", and not of the image itself. http://envisat.esa.int/handbooks/asar/CNTR6-6-9.htm#eph.asar.asardf.asarrec.ASAR_Geo_Grid_ADSR
Instead, the Y-coordinate should be calculated as a cumulative sum from the "num_lines" parameter: [1 cumsum(num_lines)] in Matlab-notation.
Note that Ticket #3160 refers to the same issue. A patch is posted there, but I am not sure if that solves the issue.
I propose to increase the priority of this ticket, as Envisat is one of the major satellites, and the data are not very useful without georeferencing.
comment:5 Changed 10 years ago by
Priority: | normal → high |
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comment:6 Changed 10 years ago by
Cc: | Even Rouault added |
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comment:7 Changed 10 years ago by
(I see you've cc'ed me. Just to mention I have no particular competence/interest on this file format and don't intend to take any particular action on this)
comment:8 Changed 10 years ago by
Cc: | antonio added |
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comment:9 Changed 10 years ago by
I have recompiled GDAL with the patch which was posted by Antonio in Ticket #3160, and can confirm that it solves the problem.
Are there any developers who would like to apply this patch to the official repository, and then close these two tickets (#3160 and #3709)?
http://trac.osgeo.org/gdal/attachment/ticket/3160/gdal-envisat-gcp.patch
comment:10 Changed 10 years ago by
Milestone: | → 1.8.1 |
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Resolution: | → fixed |
Status: | assigned → closed |
Chaitanya,
Could you see if you can find envisat data to replicate this? It may be hard to find some.