[Geotools-devel] Help with GeoTools : Trouble transforming coordinates
Hello everyone,
I hope this message finds you well.
My name is Mourad Harmim, a Data Engineer consultant from France.
Still getting used to GeoTools, I’m facing an issue when I try to transform
coordinates from Lambert 2 extended (EPSG :27572) to Lambert 93 (EPSE :2154).
Here is my current situation :
* When I use : this.mathTransform =
CRS.findMathTransform(CRS.decode("EPSG:27572") , CRS.decode("EPSG:2154"),
false) there is an error telling that Bursa Wolf parameters are missing
* When I use : this.mathTransform =
CRS.findMathTransform(CRS.decode("EPSG:27572") , CRS.decode("EPSG:2154"), true)
I get coordinates but they seem inaccurate (I guess it is about a missing grid
shift)
* When I use intermediate system : Lambert 2 extended (EPSG :27572) to
WSG84 (EPSG:4326) to Lambert 93 (EPSE :2154) I get better results but still
inaccurate.
I would like to know what it is the correct approch to have an accurate
transformation between these two systems.
I hope that it is not inappropriate to ask for your help through this email and
I hope to hear from you soon.
Thank you.
Mourad Harmim.
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Re: [Geotools-devel] Help with GeoTools : Trouble transforming coordinates
Hello everyone,
Unfortunately I could not find any clues in the public resources.
Should I try a specifc version of GeoTools java dependency ?
Any suggestion is warmly welcomed.
Thank you,
Mourad Harmim.
De : Mourad HARMIM
Envoyé : lundi 15 juillet 2024 09:52
À : Jody Garnett
Objet : RE: [Geotools-devel] Help with GeoTools : Trouble transforming
coordinates
Hello Jody,
Thank you for your early reply.
I actually added the dependency gt-epsg-hsql where the thecoordinate references
are supposed to be.
I also tried passing wkt definitions (which reliability are not sure) but still
not working.
I'll lookup the guide you provided. Let's keep in touch.
Best regards,
Mourad Harmim.
De : Jody Garnett
Envoyé : lundi 15 juillet 2024 03:08
À : Mourad HARMIM
Cc : geotools-devel@lists.sourceforge.net
;
geotools-gt2-us...@lists.sourceforge.net
Objet : Re: [Geotools-devel] Help with GeoTools : Trouble transforming
coordinates
The user list is the right place to ask.
I do not work on the coordinate reference system so much myself, there is a
handy guide for configuring here:
https://docs.geoserver.org/main/en/user/configuration/crshandling/index.html
Using this approach you can provide the transform, however I am curious why
GeoTools does not have the required information. Are you using gt-epsg-shall
for definitions or the wkt one?
If you look up online can you compare the information to what is included in
GeoTools?
--
Jody Garnett
On Sun, Jul 14, 2024 at 5:31 PM Mourad HARMIM
mailto:mourad.har...@live.fr>> wrote:
Hello everyone,
I hope this message finds you well.
My name is Mourad Harmim, a Data Engineer consultant from France.
Still getting used to GeoTools, I’m facing an issue when I try to transform
coordinates from Lambert 2 extended (EPSG :27572) to Lambert 93 (EPSE :2154).
Here is my current situation :
* When I use : this.mathTransform =
CRS.findMathTransform(CRS.decode("EPSG:27572") , CRS.decode("EPSG:2154"),
false) there is an error telling that Bursa Wolf parameters are missing
* When I use : this.mathTransform =
CRS.findMathTransform(CRS.decode("EPSG:27572") , CRS.decode("EPSG:2154"), true)
I get coordinates but they seem inaccurate (I guess it is about a missing grid
shift)
* When I use intermediate system : Lambert 2 extended (EPSG :27572) to
WSG84 (EPSG:4326) to Lambert 93 (EPSE :2154) I get better results but still
inaccurate.
I would like to know what it is the correct approch to have an accurate
transformation between these two systems.
I hope that it is not inappropriate to ask for your help through this email and
I hope to hear from you soon.
Thank you.
Mourad Harmim.
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Re: [Geotools-devel] Help with GeoTools : Trouble transforming coordinates
Hello Ian,
Thank you for your reply.
Unfortunatly a was unable to find a corresponding grid shift nor the right
parameters for this specific transformation.
What is suprising is epsg.io online transformer it is actually possible to do
it : Transform coordinates - GPS online converter
(epsg.io)<https://epsg.io/transform#s_srs=27572&t_srs=2154&x=601218.2709050&y=2428184.1367070>
I found the source code of epsg.io and they implemented the transformation
using "osr" library in python : epsg.io/app.py at master · maptiler/epsg.io ·
GitHub<https://github.com/maptiler/epsg.io/blob/master/app.py#L1380>
However I could not find anything similair in java.
Kind regards,
Mourad Harmim.
De : Ian Turton
Envoyé : jeudi 1 août 2024 10:32
À : Mourad HARMIM
Cc : geotools-gt2-us...@lists.sourceforge.net
;
geotools-devel@lists.sourceforge.net
Objet : Re: [Geotools-devel] Help with GeoTools : Trouble transforming
coordinates
>From a quick look on epsg.io<http://epsg.io> there seems not to be a direct
>transform from 27572 to 2154 so that is why the TOWGS or Bursa Wolf transform
>is needed. These would appear to have a 2m accuracy so some transformation
>error is to be expected.
If you have a grid shift or other transformation file available then you can
add it to GeoTools as described here -
https://gis.stackexchange.com/questions/313512/specifying-epsg-transformation-method-in-geotools/313523#313523
Ian
On Mon, 15 Jul 2024 at 01:31, Mourad HARMIM
mailto:mourad.har...@live.fr>> wrote:
Hello everyone,
I hope this message finds you well.
My name is Mourad Harmim, a Data Engineer consultant from France.
Still getting used to GeoTools, I’m facing an issue when I try to transform
coordinates from Lambert 2 extended (EPSG :27572) to Lambert 93 (EPSE :2154).
Here is my current situation :
* When I use : this.mathTransform =
CRS.findMathTransform(CRS.decode("EPSG:27572") , CRS.decode("EPSG:2154"),
false) there is an error telling that Bursa Wolf parameters are missing
* When I use : this.mathTransform =
CRS.findMathTransform(CRS.decode("EPSG:27572") , CRS.decode("EPSG:2154"), true)
I get coordinates but they seem inaccurate (I guess it is about a missing grid
shift)
* When I use intermediate system : Lambert 2 extended (EPSG :27572) to
WSG84 (EPSG:4326) to Lambert 93 (EPSE :2154) I get better results but still
inaccurate.
I would like to know what it is the correct approch to have an accurate
transformation between these two systems.
I hope that it is not inappropriate to ask for your help through this email and
I hope to hear from you soon.
Thank you.
Mourad Harmim.
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--
Ian Turton
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