Re: Status and future of the GDAL GNM and image correlator

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Very recently {terra} has added SpatNetwork which utilizes/works-with GNM:
https://github.com/rspatial/terra/blob/master/src/spatNetwork_gnm.cpp so
that might be of interest.

Cheers, Mike


On Wed, May 27, 2026 at 6:26=E2=80=AFPM Even Rouault via gdal-dev <
[email protected]> wrote:

> Hi Alex,
> > More than ten years ago, two features were added to GDAL during GSoC
> > projects: the raster correlator [0] and support for the Geographic
> > Network Model (GNM) [1]. Both features seem to have remained
> > limited/experimental, with almost no activity except for code
> > formatting and compilation fixes.
> True
> > As far as I know, they also are
> > rarely included in default builds by major distributions/packages,
> Are you sure about that ? The raster correlator is part of the build and
> cannot be disabled easily, and even if GNM can be disabled, it is on by
> default. Debian or conda-forge builds include it for example
> > the correlator API is not exposed via SWIG.
> True
> >
> > I wonder what is the status and future of this code? Are there any
> > plans to improve and expose it, or is the project leaning toward
> > deprecation and removal to reduce maintenance overhead?
>
> I was also wondering lately. We also don't see bug reports or questions
> related to them, so they might be little used.
>
> And the fact that gnmanalyze & gnmmanage haven't been ported to the new
> CLI will not help build awareness around them.
>
> Those features don't get that much in our way so there's no immediate
> need to consider deprecation
>
> > In the past I developed an experimental QGIS plugin that uses GDAL GNM
> > via Python bindings and considered exposing the correlator as well.
> In the same plugin ?
> > I would love to hear your thoughts on the future of these two features
> > before investing further into plugins, and potentially to the GDAL.
>
> It might be a chicken & egg problem: not enough exposed =3D=3D> not enoug=
h
> used =3D=3D> no feedback =3D=3D> no change.
>
> But what's true is that the original developers are apparently no longer
> available (I pinged recently for a GNM related pull request and got no
> feedback).
>
> Even
>
> --
> Very grumpy about LLMs: FOSS is about increasing public capital,
> not becoming enslaved to private equity of giga corporations
> --
> http://www.spatialys.com
> My software is free, but my time generally not.
>
> _______________________________________________
> gdal-dev mailing list
> [email protected]
> https://lists.osgeo.org/mailman/listinfo/gdal-dev
>


--=20
Michael Sumner
Research Software Engineer
Australian Antarctic Division
Hobart, Australia
0438489030
e-mail: [email protected]

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<div dir=3D"ltr">Very recently {terra} has added SpatNetwork which utilizes=
/works-with GNM:=C2=A0<a href=3D"https://github.com/rspatial/terra/blob/mas=
ter/src/spatNetwork_gnm.cpp">https://github.com/rspatial/terra/blob/master/=
src/spatNetwork_gnm.cpp</a> so that might be of interest.=C2=A0<div><br></d=
iv><div>Cheers, Mike</div><div><br></div></div><br><div class=3D"gmail_quot=
e gmail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, May =
27, 2026 at 6:26=E2=80=AFPM Even Rouault via gdal-dev &lt;<a href=3D"mailto=
:[email protected]">[email protected]</a>&gt; wrote:<br></div=
><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border=
-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Alex,<br>
&gt; More than ten years ago, two features were added to GDAL during GSoC<b=
r>
&gt; projects: the raster correlator [0] and support for the Geographic<br>
&gt; Network Model (GNM) [1]. Both features seem to have remained<br>
&gt; limited/experimental, with almost no activity except for code<br>
&gt; formatting and compilation fixes.<br>
True<br>
&gt; As far as I know, they also are<br>
&gt; rarely included in default builds by major distributions/packages,<br>
Are you sure about that ? The raster correlator is part of the build and <b=
r>
cannot be disabled easily, and even if GNM can be disabled, it is on by <br=
>
default. Debian or conda-forge builds include it for example<br>
&gt; the correlator API is not exposed via SWIG.<br>
True<br>
&gt;<br>
&gt; I wonder what is the status and future of this code? Are there any<br>
&gt; plans to improve and expose it, or is the project leaning toward<br>
&gt; deprecation and removal to reduce maintenance overhead?<br>
<br>
I was also wondering lately. We also don&#39;t see bug reports or questions=
 <br>
related to them, so they might be little used.<br>
<br>
And the fact that gnmanalyze &amp; gnmmanage haven&#39;t been ported to the=
 new <br>
CLI will not help build awareness around them.<br>
<br>
Those features don&#39;t get that much in our way so there&#39;s no immedia=
te <br>
need to consider deprecation<br>
<br>
&gt; In the past I developed an experimental QGIS plugin that uses GDAL GNM=
<br>
&gt; via Python bindings and considered exposing the correlator as well.<br=
>
In the same plugin ?<br>
&gt; I would love to hear your thoughts on the future of these two features=
<br>
&gt; before investing further into plugins, and potentially to the GDAL.<br=
>
<br>
It might be a chicken &amp; egg problem: not enough exposed =3D=3D&gt; not =
enough <br>
used =3D=3D&gt; no feedback =3D=3D&gt; no change.<br>
<br>
But what&#39;s true is that the original developers are apparently no longe=
r <br>
available (I pinged recently for a GNM related pull request and got no <br>
feedback).<br>
<br>
Even<br>
<br>
-- <br>
Very grumpy about LLMs: FOSS is about increasing public capital,<br>
not becoming enslaved to private equity of giga corporations<br>
--<br>
<a href=3D"http://www.spatialys.com" rel=3D"noreferrer" target=3D"_blank">h=
ttp://www.spatialys.com</a><br>
My software is free, but my time generally not.<br>
<br>
_______________________________________________<br>
gdal-dev mailing list<br>
<a href=3D"mailto:[email protected]" target=3D"_blank">gdal-dev@list=
s.osgeo.org</a><br>
<a href=3D"https://lists.osgeo.org/mailman/listinfo/gdal-dev" rel=3D"norefe=
rrer" target=3D"_blank">https://lists.osgeo.org/mailman/listinfo/gdal-dev</=
a><br>
</blockquote></div><div><br clear=3D"all"></div><div><br></div><span class=
=3D"gmail_signature_prefix">-- </span><br><div dir=3D"ltr" class=3D"gmail_s=
ignature"><div dir=3D"ltr"><div dir=3D"ltr" style=3D"color:rgb(34,34,34)"><=
div dir=3D"ltr">Michael Sumner</div><div dir=3D"ltr">Research Software Engi=
neer<br>Australian Antarctic Division<br>Hobart, Australia</div><div dir=3D=
"ltr">0438489030<br>e-mail:=C2=A0<a href=3D"mailto:[email protected]" styl=
e=3D"color:rgb(17,85,204)" target=3D"_blank">[email protected]</a></div></=
div></div></div>

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