Opened 3 months ago

Closed 3 months ago

Last modified 3 months ago

#6992 closed defect (fixed)

Bug writing GSAG formatted files

Reported by: davisnn Owned by: warmerdam
Priority: normal Milestone: 2.1.5
Component: default Version: 2.2.0
Severity: normal Keywords:
Cc:

Description

I have been using GDAL to convert Viewfinder DEM data (HGT format) to the GSAG format. I found that for many of these files there are issues with the GSAG output.

All tests were carried out using GDAL 2.2.0 that was installed using the conda package manager from the Conda Forge respository on an Ubuntu Linux system.

The data can be downloaded from http://viewfinderpanoramas.org/dem3/K33.zip. I have attached a Jupyter Notebook that runs through the translation, and produces some of the results of my tests.

In summary, the conversion of the file to GeoTiff? always produces differences of 0, while converting to GSAG there are often large differences. I found that if I clipped the domain to a smaller region, in the case of the file N41E013.hgt, 385 pixels starting from pixel 200, I would get no differences, but if I included a 386th pixel the differences would show up. This was not true however if I tried starting from pixel 100, as when starting there both 385 and 386 points would work.

Please let me know if there is other information that I can provide, or if there is a systematic way that I can help to test this.

Attachments (1)

test_gdal_translate.ipynb (8.7 KB) - added by davisnn 3 months ago.
IPython Notebook showing steps I tried to test the conversion

Download all attachments as: .zip

Change History (7)

Changed 3 months ago by davisnn

Attachment: test_gdal_translate.ipynb added

IPython Notebook showing steps I tried to test the conversion

comment:1 Changed 3 months ago by Even Rouault

Resolution: fixed
Status: newclosed

In 39764:

GSAG: fix reading issue that could cause a spurious 0 value to be read and shift all following values (fixes #6992)

comment:2 Changed 3 months ago by Even Rouault

In 39765:

GSAG: fix reading issue that could cause a spurious 0 value to be read and shift all following values (fixes #6992)

comment:3 Changed 3 months ago by Even Rouault

In 39766:

GSAG: fix reading issue that could cause a spurious 0 value to be read and shift all following values (fixes #6992)

comment:4 Changed 3 months ago by Even Rouault

Milestone: 2.1.5

Note: the issue probably applies to even older versions.

comment:5 Changed 3 months ago by Even Rouault

Note: the issue was on the read side, not the write side

comment:6 Changed 3 months ago by davisnn

Great, thank you for the fix, and good to know that it was only on the read side.

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