These are important options. It would be nice if they could be
implemented in gdal_grid itself. Not sure how difficult that would be,
though.
Jan
On 11/21/2019 5:21 PM, Rahkonen Jukka (MML) wrote:
Hi Joaquim,
GMT surface probably has all the features that I need. I followed the tutorial
and managed to run surface demos, now I just need to learn how to use my own
data as input.
-Jukka-
-----Alkuperäinen viesti-----
Lähettäjä: Joaquim Manuel Freire Luís <jl...@ualg.pt>
Lähetetty: keskiviikko 20. marraskuuta 2019 0.30
Vastaanottaja: Even Rouault <even.roua...@spatialys.com>;
gdal-dev@lists.osgeo.org
Kopio: Rahkonen Jukka (MML) <jukka.rahko...@maanmittauslaitos.fi>
Aihe: RE: [gdal-dev] Gdal_grid and lake bathymetry
The GMT surface program has two (well 3) options that are of interest to this.
-One, the -Lu<upper> that serves to limit the upper value in the interpolated
grid
-The other is the option -D that lets you set a soft-breakline (your shorelines).
Soft-breaklines are lines whose vertex end up in the grid nodes closest to them. They are
called "soft" in contraposition to the hard-breaklines that do not let the
interpolation algorithm go across them. Imagine interpolation a terrain with vertical
cliffs. Unfortunately that -D option is missing on the html man page but is described on
the surface on line help.
-Finally, option -M lets you mask the outside lakes region
https://docs.generic-mapping-tools.org/latest/surface.html
Joaquim
-----Original Message-----
From: gdal-dev <gdal-dev-boun...@lists.osgeo.org> On Behalf Of Even Rouault
Sent: Tuesday, November 19, 2019 10:13 PM
To: gdal-dev@lists.osgeo.org
Cc: Rahkonen Jukka (MML) <jukka.rahko...@maanmittauslaitos.fi>
Subject: Re: [gdal-dev] Gdal_grid and lake bathymetry
On mardi 19 novembre 2019 22:03:29 CET Rahkonen Jukka (MML) wrote:
Hi,
I would like to get some hints about using gdal_grid or some other
utility for lake bathymetry. What I have is typically rather sparse
point data of depths and the shoreline that includes the islands as in
the attached image. The shoreline and all the area that is not lake
basin should have the altitude of zero in the resulting DEM. It means
that interpolation should not overshoot across the shoreline over the dry land.
Gdal_grid seems to miss an option for handling the shoreline so I made
a test by converting the vertices of the polygon rings into depth
points. I also filled area around the lake with a gridded points of
zero altitude but the method feels stupid and tedious and the result
was not so fine when it comes to keep the shoreline and land area near it
totally flat.
Postprocessing with gdalwarp -cutline to set to zero non-lake areas ?
--
Spatialys - Geospatial professional services http://www.spatialys.com
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