[OSM-talk] Own maps with hill shading and routes using mapnik

[Andy Allan]

On Mon, Sep 15, 2008 at 11:08 PM, David Earl <david at frankieandshadow.com> wrote:
> On 15/09/2008 22:07, Donald Allwright wrote:
>> The theory is that
>> if the SRTM data include an altitude reading for the lake itself (I
>> haven't actually checked this yet!), I should be able to use an approach
>> similar to what you suggest to get a much more accurate map. The holy
>> grail would be to be able to click somewhere within a lake, and the
>> software to automatically generate a perimeter. However I suspect that
>> will be a long way off, if it ever happens.
>
> But will the accuracy be any better? SRTM seems to be 3 arc seconds
> outside the USA = approx 90m of latitude per pixel.

Absolutely. I can see the idea, but if there's Yahoo or even Landsat
imagery it'll most likely be more accurate that way to get lakes.

And don't be fooled by the contours on the cycle map - they might be
thin and look really accurate, but they are just massive
extrapolations from relatively low-resolution DEMs. Most lakes have
one or two contours running underneath them at the moment, some rivers
run uphill in some places (especially in narrow gorges) and so on.

Cheers,
Andy