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First of all, let me say that I know next to nothing about GISs.

I'm trying to find / make / aquire a topographical map of britain. I want to use it as a height map in Dwarf Fortress so it needs to be gradient grayscale, without labels and bmp format.

I've done some googling and so far haven't found any maps I could use, free or otherwise. Which seems absurd, so I must be looking for the wrong thing?

It seems possible to retrieve the height from Google Maps API. My first thought is to make a program that requests the height for every coordinate from Google. Leave the program running for a week and then construct an image from the data.

Though I thought I should ask here to see if people look at me like I'm crazy!?

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Google "Great Britain DEM". One good hit (an overview) is at guides.archaeologydataservice.ac.uk/… . –  whuber Jun 4 '11 at 22:19
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You only have a 2500 request per IP address in 24hrs - Use of the Google Elevation API is subject to a limit of 2,500 requests per day (Premier users may send up to 100,000 requests per day). In each given request you may query the elevation of up to 512 locations, but you may not exceed 25,000 total locations per day (1,000,000 for Premier users). This limit is enforced to prevent abuse and/or repurposing of the Elevation API, and this limit may be changed in the future without notice. code.google.com/apis/maps/documentation/elevation –  Mapperz Jun 4 '11 at 23:04
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4 Answers

You need to download the Land-Form Panorama OpenData (OpenData=free) dataset from Ordnance Survey

Download is for Great Britain only (England, Scotland & Wales only) 530MB

https://www.ordnancesurvey.co.uk/opendatadownload/products.html

Pros:

FREE This product is supplied both as a set of contours and spot heights (x,z,y) and as a gridded digital terrain model (DTM).

enter image description here

Cons:

Lots of processing of the data (some manual work)

Panorama data was collected between 1970 and 1980. This product has not been updated since this date. DXF format not the easiest to convert

Broken Contours - they do not link back to start so polygons cannot be created.

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Based on your use-case, I'm guessing you won't need extremely high resolution data (many users are looking for 90 meter or better data) and are more interested in the consistency and visual presentation aspects of the data than its precise accuracy at a cell level. A nice dataset for this kind of use is CleanTOPO2, a global nominally 1km resolution dataset which contains both elevations and water depths. Its provided in a Greyscale GeoTIFF format.

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This link is unfortunately broken. –  ASGM Mar 26 '13 at 18:04
    
The CleanTOPO2 link above works fine for me. What error are you getting? –  scw Mar 27 '13 at 7:49
    
This is very odd. When I click on the link in your answer, or copy and paste it into the browser, I get one of those generic landing pages with spam links all over the place. But if I type the link myself into the browser, as long as I don't include www, I get to the page you were linking to. I can't explain it, but if I'm the only one to experience it so far I wouldn't worry too much. –  ASGM Mar 27 '13 at 12:48
    
You might want to check your machine for malware -- it sounds like a third-party application is hijacking links. –  scw Mar 28 '13 at 7:48
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Are you looking for a height map or a topo map? These are not exactly the same.

If you want a grayscale (or any other scale for that matter) height map of Britain, one of the ways you can get that is using Maperitive's generate-hypsometric command.

Here's a sample heightmap I've just made for the northern Scotland (black is zero elevation, white is 1500m in this sample):enter image description here

(full size version: http://www.flickr.com/photos/breki74/5798326460/sizes/o/in/photostream/).

The command I used is: generate-hypsometric ramps=0:black;1500:white

Maperitive uses SRTM data, which is free, but can contain voids. Also note that the lat/lon resolution is around 90m and you won't be able to generate the whole Britain bitmap in one go, because it's just too large.

One question though: why BMP? It's a lousy format for these things.

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Grab the strm data for the UK from here: http://dds.cr.usgs.gov/srtm/version2_1/ noting in particular the documentation that explains the naming system for the files.

Once you have the appropriate hgt files, use gdaldem like these examples: http://nelsonslog.wordpress.com/2010/12/15/gdaldem-for-srtm-translation/ or http://linfiniti.com/2010/12/a-workflow-for-creating-beautiful-relief-shaded-dems-using-gdal/ which will give you a png or a tiff or for each hgt file.

You will then need to stitch them all together into one if you really need one single file for the whole of the UK- you can use another gdal tool for this- gdal_merge. If you're not keen on command line stuff, then the gdal tools can be used within Quantum GIS.

Finally, convert the resulting tiff or png (which might be huge) to a bmp file using your normal image program.

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