Re: [gdal-dev] Troubles with PAM file

[Dominique Lyszczarz]

If it can be useful to anyone facing the same issue, my little script for
parsing these aux.xml and writing the expected GDAL commands to rectify the
raster is available here https://github.com/domlysz/PAM-GCPs-warper

Regards

Le mer. 20 mars 2019 à 18:09, Dominique Lyszczarz  a
écrit :

> Thank you Even for these informations, that's good to know. I've added the
> .aux.xml in the repository if it can be useful as reference. Finally, I got
> good results with gdal_translate -gcp option following by gdalwarp. Fun
> fact, in the PAM file Y image coordinates are negatives values but must be
> pushed as positive number in gdal_translate command.
>
> Le mer. 20 mars 2019 à 15:57, Even Rouault  a
> écrit :
>
>> Dominique,
>> >
>> > I'm trying to read a raster georeferenced with ArcGIS. It's a jpg file
>> > coming with a PAM file (.aux.xml) that store GCPs and define a
>> polynomial
>> > transformation of order 3. Unfortunately GDAL does not take the PAM file
>> > into account and gdalinfo does not report GCPs. After some
>> investigations,
>> > I found this commit
>> > <
>> https://github.com/OSGeo/gdal/commit/f8822eb50466fb740e228b8c6a7f066b916faa
>> > 0a> that suggest PAM files are supported by GDAL but only for TIFF
>> dataset.
>>
>> Not really. PAM files are supported for most formats, included JPEG, but
>> the
>> ESRI specific GCP decoding was limited for now to the GTiff format,
>> mostly
>> because of the oddity you noticed: in the case for which this was
>> developed
>> for
>> (see https://lists.osgeo.org/pipermail/gdal-dev/2017-January/045854.html
>> and
>> the related email thread), pixel coordinates were indeed surprisingly in
>> inches and from the bottom left origin. So I couldn't/didn't want to
>> generalize that to core PAM processing.
>>
>> >
>> > I'm a bit confused with theses PAM files, is there any technical doc
>> from
>> > ESRI?
>>
>> Not to my knowledge. Initially PAM was developed for GDAL itself, but it
>> seems
>> ESRI developed some extensions on top of it, like the one you are facing
>> to.
>>
>> > The file can be downloaded here :
>> >
>> https://drive.google.com/drive/folders/1hZXncJhcfZI0Uem-oCfUsruO9mPwWD0U?usp
>> > =sharing
>>
>> You didn't include the most interesting part, that is the .aux.xml file
>> itself
>>
>> Even
>>
>> --
>> Spatialys - Geospatial professional services
>> http://www.spatialys.com
>>
>
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Re: [gdal-dev] Troubles with PAM file

[Dominique Lyszczarz]

Thank you Even for these informations, that's good to know. I've added the
.aux.xml in the repository if it can be useful as reference. Finally, I got
good results with gdal_translate -gcp option following by gdalwarp. Fun
fact, in the PAM file Y image coordinates are negatives values but must be
pushed as positive number in gdal_translate command.

Le mer. 20 mars 2019 à 15:57, Even Rouault  a
écrit :

> Dominique,
> >
> > I'm trying to read a raster georeferenced with ArcGIS. It's a jpg file
> > coming with a PAM file (.aux.xml) that store GCPs and define a polynomial
> > transformation of order 3. Unfortunately GDAL does not take the PAM file
> > into account and gdalinfo does not report GCPs. After some
> investigations,
> > I found this commit
> > <
> https://github.com/OSGeo/gdal/commit/f8822eb50466fb740e228b8c6a7f066b916faa
> > 0a> that suggest PAM files are supported by GDAL but only for TIFF
> dataset.
>
> Not really. PAM files are supported for most formats, included JPEG, but
> the
> ESRI specific GCP decoding was limited for now to the GTiff format, mostly
> because of the oddity you noticed: in the case for which this was
> developed
> for
> (see https://lists.osgeo.org/pipermail/gdal-dev/2017-January/045854.html
> and
> the related email thread), pixel coordinates were indeed surprisingly in
> inches and from the bottom left origin. So I couldn't/didn't want to
> generalize that to core PAM processing.
>
> >
> > I'm a bit confused with theses PAM files, is there any technical doc from
> > ESRI?
>
> Not to my knowledge. Initially PAM was developed for GDAL itself, but it
> seems
> ESRI developed some extensions on top of it, like the one you are facing
> to.
>
> > The file can be downloaded here :
> >
> https://drive.google.com/drive/folders/1hZXncJhcfZI0Uem-oCfUsruO9mPwWD0U?usp
> > =sharing
>
> You didn't include the most interesting part, that is the .aux.xml file
> itself
>
> Even
>
> --
> Spatialys - Geospatial professional services
> http://www.spatialys.com
>
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Re: [gdal-dev] Troubles with PAM file

[Even Rouault]

Dominique,
> 
> I'm trying to read a raster georeferenced with ArcGIS. It's a jpg file
> coming with a PAM file (.aux.xml) that store GCPs and define a polynomial
> transformation of order 3. Unfortunately GDAL does not take the PAM file
> into account and gdalinfo does not report GCPs. After some investigations,
> I found this commit
>  0a> that suggest PAM files are supported by GDAL but only for TIFF dataset.

Not really. PAM files are supported for most formats, included JPEG, but the 
ESRI specific GCP decoding was limited for now to the GTiff format, mostly 
because of the oddity you noticed: in the case for which this was developed 
for
(see https://lists.osgeo.org/pipermail/gdal-dev/2017-January/045854.html and 
the related email thread), pixel coordinates were indeed surprisingly in 
inches and from the bottom left origin. So I couldn't/didn't want to 
generalize that to core PAM processing.

> 
> I'm a bit confused with theses PAM files, is there any technical doc from
> ESRI? 

Not to my knowledge. Initially PAM was developed for GDAL itself, but it seems 
ESRI developed some extensions on top of it, like the one you are facing to.

> The file can be downloaded here :
> https://drive.google.com/drive/folders/1hZXncJhcfZI0Uem-oCfUsruO9mPwWD0U?usp
> =sharing

You didn't include the most interesting part, that is the .aux.xml file itself

Even

-- 
Spatialys - Geospatial professional services
http://www.spatialys.com
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[gdal-dev] Troubles with PAM file

[Dominique Lyszczarz]

Hi all,

I'm trying to read a raster georeferenced with ArcGIS. It's a jpg file
coming with a PAM file (.aux.xml) that store GCPs and define a polynomial
transformation of order 3. Unfortunately GDAL does not take the PAM file
into account and gdalinfo does not report GCPs. After some investigations,
I found this commit

that suggest PAM files are supported by GDAL but only for TIFF dataset. So,
I've translated my file to TIFF and now gdalinfo report the GCPs but the
file is not correctly georeferenced. Reading more carefully the commit
previously cited I can see some relevants clues : sources GPCs are
considered to be expressed in inch and so the code rely on image dpi stored
in TIFF tags to compute the pixels coordinates. Futhermore the origin of
pixels coordinates is considered to be the bottom left. I've checked my PAM
file and clearly the sources GPC are expressed directly in pixel, not inch,
with an image origin fixed to top left. I can set the dpi of my image to 1
to fix the scale but Y coordinates remains wrong.

I'm a bit confused with theses PAM files, is there any technical doc from
ESRI? My PAM file make sense for me : pixel coordinates and top left origin
(like worldfile) for sources GPC, it's seems a very common approach. But
inch !? Also is there any particular reason to limit PAM file reading to
TIFF dataset ? maybe is it related to the need to extract dpi from tags ?

For now I can't see any way to correctly read this file with GDAL, so I'm
thinking of writing my own script to parse GCPs and rectify the raster wih
gdalwarp. Not sure if it will be the best approach here, any advices?

The file can be downloaded here :
https://drive.google.com/drive/folders/1hZXncJhcfZI0Uem-oCfUsruO9mPwWD0U?usp=sharing

Thanks in advance for any feedback on this.

Regards
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