DEM more precise

Bernard Perrot shared this question 2 months ago
In Progress

Hello,

In France, we have now DEM data with a very high accuracy, from national IGN, with cell size of 5mx5m. No problem to convert datum and file format.

But, if I understood well, in Locus Map, only HGT files are know, so, it is impossible to convert these IGN DEM to HGT, because HGT are 1" arc cell size (about 25m).

Is there another way to use these 5m DEM in Locus ?

If not, may be a good idea to permit other DEM file format (like BIL/HDR or other) in Locus non ?

Best regards,

Comments (5)

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France already had those high-resolution DTM files for several years. The problem has been, that those files were not for free use, i.e. no Open Data. So for my LiDAR-DTMs I had to to use the free available IGN 75m for those areas of France where no high-resolution LiDAR data of other sources is available.


Do you know if IGN 5m is Open Data now?

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Hello Sonny,

Yes, they are free now, since 1st of January. Under "Etalab" open licence.

The RGE-ALTI at 5m is available at this adress : https://geoservices.ign.fr/documentation/diffusion/telechargement-donnees-libres.html#rge-alti-5m

But your files are formatted as SRTM/HGT, this format is limited up to 1" arc (about 25m in France).

So, my question...

Best regards,

PS : Sonny, I asked you directly by mail a few days ago how to write HGT files... I have found, using QGIS. But limited to 3601x3601 pixels for 1"... so...

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@Bernard - please check the following topic https://help.locusmap.eu/topic/srtm-hgt-file-handling#comment-91531 Where are mentioned some tips how to create more detailed elevation files.

We'll be happy to use sonny's new data set and offer it to our users for downloading (thanks sonny).

Petr

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Hello Petr,

I'va already found this topic, but... don't really understand what to do and how... HGT files are limited to 3601 x 3601, so how to use them for more precise DEM... ?

Bernard

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Honestly, I'm not 100% sure how Markus created the more detailed files. But the hgt format can contain a more detailed grid and Locus is able to load a more detailed hgt file. Please ask Markus for more info.

Thanks, Petr

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Since some weeks LiDAR source data of the whole territory of France in its finest resolution is available as OpenData. So during the last weeks I created enhanced DTMs of France:

https://data.opendataportal.at/dataset/dtm-france


Additionally Wallonia (Souther Belgium) also provides their LiDAR sources in its finest resolution as OpenData. So I created enhanced DTMs for Belgium too, now the whole country is complete in highest resolution:

https://data.opendataportal.at/dataset/dtm-belgium


Have fun, Sonny.