[gdal-dev] How to locate where the raster min and max values are?

[Nyall Dawson]

On Tue, 5 Nov 2024 at 22:09, Rahkonen Jukka <
jukka.rahkonen at maanmittauslaitos.fi> wrote:
>
> Hi,
>
>
>
> Very nice, seems that you both took the challenge very seriously. Now an
advanced use case came into my mind, and it is about finding extreme values
of sensor data within a polygon. Brute force method is to pre-process the
raster and burn nodata into the exterior of the study area with
gdal_rasterize by using the -i (invert) option. Can you suggest something
more clever?
>
>
>
> Right now I am just curious, but I guess that the QGIS Zonal statistics
tool min/max option with additional x and y coordinate fields could make
some users happy, or “gdal_minmax_location.py” with a -mask option.

Good idea! I've added a corresponding tool in
https://github.com/qgis/QGIS/pull/59358 🥳

Nyall

>
>
>
> -Jukka Rahkonen-
>
>
>
> Lähettäjä: Nyall Dawson <nyall.dawson at gmail.com>
> Lähetetty: tiistai 5. marraskuuta 2024 2.51
> Vastaanottaja: Even Rouault <even.rouault at spatialys.com>
> Kopio: Rahkonen Jukka <jukka.rahkonen at maanmittauslaitos.fi>; '
gdal-dev at lists.osgeo.org' (gdal-dev at lists.osgeo.org) <
gdal-dev at lists.osgeo.org>
> Aihe: Re: [gdal-dev] How to locate where the raster min and max values
are?
>
>
>
>
> >
> > I would like to know the georeferenced coordinates of the min and max
values of a DEM file. Even better if I could forward them into a vector
file. If the minimum or maximum happens to be on a flat area like seabed I
would be happy with the first pixel at the moment.
> >
> > The task feels rather simple and I was sure that someone has already
made an utility or a QGIS plugin, but all I have found yet is for R
>
> I've submitted a processing tool for QGIS 3.42 to do this here:
https://github.com/qgis/QGIS/pull/59332 . This uses Even's new GDAL api so
should be super-efficient & fast to calculate. 🥳
>
>
>
> Thanks for raising this interesting discussion, a lot of nice things have
come out of this!
>
>
>
> Nyall
>
>
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