[OSM-dev] SRTM relief

Andy Allan gravitystorm at gmail.com
Wed Jan 2 22:31:12 GMT 2008


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

* Managed to get them rendering, but every .shp file makes the
rendering go more slowly, and I keep getting distracted by other
things where I can make more impact for less thrashing-around in the
dark. My ambition exceeds my coding skills somewhat :-)




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