[OSM-dev] SRTM relief

Artem Pavlenko artem.mapnik at googlemail.com
Thu Jan 3 10:44:27 GMT 2008


On 2 Jan 2008, at 23:50, Nick Whitelegg wrote:

> On Wednesday 02 Jan 2008 22:31, Andy Allan wrote:
>> On Jan 2, 2008 9:55 PM, Artem Pavlenko  
>> <artem.mapnik at googlemail.com> wrote:
>>> Hello lists,
>>>
>>> Sometime last year I was inspired by http://www.srtm.com and I even
>>> contacted developer to see if we can use SRTM derived relief maps in
>>> OSM.
>>> I don't remember all details but reply was somewhat ambiguous:  yes
>>> OSM can use pre-rendered tiles from the site above, source code (in
>>> Java ) is a bit messy, cause my crazy mate coded something ...
>>> Anyway, while srtm.com tiles look good on its own, colour scheme is
>>> not suitable for overlaying with OSM data IMHO. So I thought it  
>>> would
>>> be fairly straight forward to implement something from scratch.
>>>
>>> Here is what I'm thinking about - a c++ command line app, which  
>>> given
>>> bounding box in geographic coordinate system (WGS84) would read
>>> compressed raw SRTM files and output 'nice' looking maps (tiles) in
>>> specified projection (I only care about Mercator and OS NatGrid but
>>> others will work as well).
>>>
>>> Here is more detailed feature list:
>>>
>>> 1. highly configurable
>>> 2. all steps needed to produce final relief map included (relief,
>>> blending , warping  etc)
>>> 3. read raw compressed SRTM directly
>>> 4. easy to add new algorithms
>>> 5. using GIL from Adobe for accessing pixels and implementing algos.
>>> 6. mapnik and OSM ready
>>> 7. perhaps it can be used for outputting contours as well (?)
>>>
>>> I've coded a prototype based on excellent posting on http://
>>> perrygeo.net/wordpress/?p=7 and I'm looking for a good color scheme
>>> that would work for the whole planet, any pointers?
>>>
>>> Here is some test outputs:
>>>
>>> http://artem.dev.openstreetmap.org/files/relief_osgb.png
>>> http://artem.dev.openstreetmap.org/files/srtm_relief.png
>>>
>>> (red pixels are voids and I'm yet to fill them, did someone  
>>> mentioned
>>> some good algorithms a few months ago?)
>>>
>>> The kind of reliefs I think might work well for OSM are gmap terrain
>>> or perhaps Yahoo style.
>>> Any ideas or comments? Cartographers?
>>
>> WANT.
>>
>> :-)
>>
>> I'd like on the cycle map to show relief at low zoom, and something
>> approaching the "Color ramps" from that linked blog post at high zoom
>> (relief is generally impossible to make out when you get zoomed in  
>> too
>> far). The thing I've been wanting and getting nowhere towards is both
>> of those concepts with contours too (for a bit of precision), so if
>> this tool of yours can do contours, relief and colour ramps then I
>> could fiddle with the colours till the cows come home. Which is all I
>> want to do really, since I've pretty much sucked at getting contours
>> done myself*
>>
>> Cheers,
>> Andy
>
> Hello Andy,
>
> There is the srtm2shp utility available in SVN which outputs a  
> shapefile of
> contours, it outputs in Mercator - is that any good? It doesn't  
> deal with
> SRTM voids yet.
>

Yes, srtm2shp is what I was thinking of using.
> Nick
Artem




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