Author Topic: What DEM (elevation) formats are supported in Locus?  (Read 823 times)

Offline mark03

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What DEM (elevation) formats are supported in Locus?
« on: May 23, 2021, 03:44:17 »
Apologies if this has been covered in the online documentation.  I searched for a while and could not find anything.

I have some very nice LIDAR data for my region (Washington, USA) which I would like to use within Locus.  The resolution is about 1m or a bit finer.  It is supplied as a GeoTIFF raster.

I could make images from this data using GDAL (color relief maps or hillshade maps).  But it would obviously be a lot better to have it integrated properly with another map.  Any suggestions for how to achieve this?  Is Locus capable of taking a raster format like GEMF and displaying it as elevation data instead of image data?  Or is there some format specific to DEMs which I should be targeting?

Thanks,
Mark
 

Offline Sonny

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Re: What DEM (elevation) formats are supported in Locus?
« Reply #1 on: May 23, 2021, 14:57:59 »
As far as I know, Locus just supports the fileformat of SRTM data (.hgt) right now, so you probably have to convert your .geotiffs.

There's a thread in th Helpdesk https://help.locusmap.eu/topic/please_support_geotiff_format
to add GeoTIFF support for maps, the same would apply to elevation data.
 

Offline mark03

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Re: What DEM (elevation) formats are supported in Locus?
« Reply #2 on: May 23, 2021, 18:45:30 »
It seems .hgt is not a particularly flexible format.  GDAL can read it, but also says

Quote
The driver does support creating new files, but the input data must be exactly formatted as a SRTM-3 or SRTM-1 cell. That is the size, and bounds must be appropriate for a cell.

I was not able to find more details in a couple minutes of searching, but I can dig deeper.  It sounds, however, like it may not be possible to cram modern, high-resolution digital terrain models into this ancient format.

I suppose the next best thing (quite a distant second!) is to generate color relief maps from the geotiffs and use those as map overlays.  The problem is that in any given map view, I want to distinguish a total surface relief of only a few meters.  So, e.g. 200 meters would be at one extreme end of the scale, and 205 meters would be at the other extreme.  If I move to another place on the map where the elevation range is 300-305 meters, then my pre-generated, color-coded relief map is useless...
 

Offline Menion

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Re: What DEM (elevation) formats are supported in Locus?
« Reply #3 on: May 23, 2021, 20:13:46 »
Hello Mark,
what is the problem with the SRTM-1 data format? Does it have a too low resolution for your usage?
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Offline mark03

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Re: What DEM (elevation) formats are supported in Locus?
« Reply #4 on: May 23, 2021, 22:44:52 »
what is the problem with the SRTM-1 data format? Does it have a too low resolution for your usage?

Hi Menion,
I have not delved into the SRTM formats yet.  Is the spatial grid fixed in size?  These new datasets are much more finely gridded than the SRTM data.  1x1 meter is required at a minimum, although 0.5x0.5 meter would be better.  Height resolution is about 0.1 meter.
Mark
 

Offline mark03

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Re: What DEM (elevation) formats are supported in Locus?
« Reply #5 on: May 24, 2021, 03:49:33 »
As I think about this more, it may be a job better suited for a GIS package like QGIS.  What I am trying to do is figure out exactly how high above river level a house is.

But I do think it would be neat if smartphone mapping software could take the new breed of LIDAR data and, e.g., generate custom contours with half-meter resolution.  Not very useful in mountainous regions, but in flatter areas, it could be.  Bicyclists in particular would appreciate more elevation resolution than the SRTM data gives, I think.