[OSM-dev] Altitude data & (cycle) route profiles

Karl Newman siliconfiend at gmail.com
Fri Mar 28 23:42:03 GMT 2008


On Fri, Mar 28, 2008 at 6:32 PM, Andy Allan <gravitystorm at gmail.com> wrote:

> 2008/3/27 Sjors Provoost <sjors at sprovoost.nl>:
>
> > My core objectives / deliverables are:
> >  import SRTM data as nodes (points) in OSM, for Australia
> > estimate the altitude of each node in Australia from the SRTM nodes
> > display (on the fly) an altitude profile given a route (a sequence of
> nodes)
> > estimate the altitude of each node in Australia from nearby GPS traces
> >  analyze the difference between both methods
>
> > It would be great if I can get some feedback on my proposal before the
> > deadline, so I can improve upon it.
>
> Hi Sjors,
>
> Firstly, good luck with your proposal, it sounds quite interesting to me.
>
> If I can make a suggestion it would be to think of the heights along
> each way, instead of just at nodes. If you look at the cycle map at
> http://www.gravitystorm.co.uk/osm/ you can see SRTM contours with OSM
> data overlaid. It's quite possible for a way to be straight yet cross
> a valley or a peak, and if you only look at the nodes at each end of a
> section you would miss this data. This is especially apparent for long
> straight features like motorways or roads in the USA where the gap
> between nodes can be many hundreds of metres or even kilometers, and
> the same may apply to Australia too. So instead of importing the
> heights as points and estimating the height of each node, I would
> suggest a different approach:
>
> * Import the SRTM data into a spatial database (i.e. postgis) as
> polylines (contours)
> * Calculate the points along the OSM way where the way intersects a
> contour
> * Use these points as the height data for the way
>
> Cheers,
> Andy
>

Why not: Use that spatial database (or the raw SRTM grid) to interpolate the
elevation of existing way nodes and then add "ele" tags to those nodes
instead of creating new nodes only at the grid points (and with no other
information)?

Karl
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