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I want to use the Ordnance Survey Land-Form Panorama product in some software called Maperitive, which can read custom SRTM DEM files.

The data is provided in the following formats:

DXF [Contours] ASCII grid [DTM] NTF [DTM]

https://www.ordnancesurvey.co.uk/opendatadownload/products.html (search for land-form)

Can anyone recommend a free tool or toolchain (runs on Linux or Windows) that I can use?

Tom Chance
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2 Answers2

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Try gdal_translate on the ASCII grids, part of the GDAL open-source package. Something like so (I'm on Windows):

D:\Raster\panorama_gb_DTM\DTM\ASCII\data\hp>gdal_translate -of USGSDEM -a_srs WGS84 hp40.asc hp40.dem

I had to override the output spatial reference with the -a_src flag to get this to work, and I'm not sure what coordinate system that data is in, as it ships with NO METADATA and their site isn't any help either. So you'd have to find that out for sure and then maybe force the EPSG code (EPSG:27700 for British National Grid, for example) on your output file. Here is the output DEM in QGIS:

enter image description here

Edit 1:

Looks like outside the U.S., SRTM3 is the standard, and looking at this doc (which I found here from here), the standard calls for SRTM3 to be 1201x1201 pixels, which these grids are not. Now I'm stumped. Could you just use SRTM data from the USGS instead?

SRTM3 files contain 1201 lines and 1201 samples. The rows at the north and south edges as well as the columns at the east and west edges of each cell overlap and are identical to the edge rows and columns in the adjacent cell. SRTM1 files contain 3601 lines and 3601 samples, with similar overlap.

Glorfindel
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Chad Cooper
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  • Thank you, that set me up with USGS ASCII files, but the software I'm using only supports SRTM1 and SRTM3 HGT files. I tried switching to "-of SRTMHGT" and gdal complained: > Input file size is 401, 401

    0Warning 1: The corner coordinates of the source are not properly aligned on plain latitude/longitude boundaries. ERROR 1: Image dimensions should be 1201x1201 or 3601x3601.

     – Tom Chance Oct 21 '11 at 14:33
  • @Tom Chance - see Edit 1 above. – Chad Cooper Oct 21 '11 at 14:59
  • I turned to this data because the USGS SRTM data has gaps that create ugly voids in any render, so I'm on the hunt for complete data for England and Wales. – Tom Chance Oct 21 '11 at 15:11
  • @TomChance - maybe you could mosaic the Ordinance Survey data, then -prjwin flag of gdal_translate to translate and clip to the 1201 x 1201 tiles? And yes, USGS SRTM is chock full of holes. – Chad Cooper Oct 21 '11 at 15:18
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Does this help?

http://www.uktrainsim.com/filelib-info.php?form_fileid=24984

Steve
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