[gdal-dev] Status and future of the GDAL GNM and image correlator

[Michael Sumner]

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 PM Even Rouault via gdal-dev <
gdal-dev at lists.osgeo.org> 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 ==> not enough
> used ==> no feedback ==> 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.
>
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-- 
Michael Sumner
Research Software Engineer
Australian Antarctic Division
Hobart, Australia
0438489030
e-mail: mdsumner at gmail.com
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