[gdal-dev] Sampling raster bands at irregular points

[Joaquim Manuel Freire Luís]

Another option is the GMT program grdtrack (https://docs.generic-mapping-tools.org/dev/grdtrack.html). It's pure C and extremely fast.

-----Original Message-----
From: gdal-dev <gdal-dev-bounces at lists.osgeo.org> On Behalf Of Felix
Sent: Thursday, December 3, 2020 1:16 PM
To: gdal-dev at lists.osgeo.org
Subject: [gdal-dev] Sampling raster bands at irregular points

Hello All,

I'm here for some suggestions on how to sample from a raster band at _non-regular_ points. Non-regular in this context means that the points have arbitrary coordinates and do not lie on a regular lattice/mesh like all pairs of integers would do.

In my application, there is an irregular set of points for which we require bathymetric data (i.e. topographical data/elevation). I started out by manually reading in the ETOPO1 dataset (for now, we might use
Earth2014 later) and then interpolating around each point sequentially. 
As we have up to hundred-tousands of points and doing the computation sequentially in Python/numpy, this is currently running for days (well, we canceled it at that point).

Ideally, I'd like to use something like the "gdal_grid" tool, where the interpolation algorithm can be configured and the heavy-lifting is done in C rather than in Python. But it only supports creating a new _regular_ grid. The inverse distance interpolation with cutoff radii would be ideal.

Does such a tool/such functionality exist in in GDAL or was my search rightfully fruitless? I mainly searched in the raster programs, the
(C++) API of GDALRasterBand and of course generally in the internet. 
Thank you for your suggestions, in advance!

Cheers and Stay Safe
Felix Divo

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