[Talk-GB] OS OpenData contours

Richard Bullock rb357 at cantab.net
Mon Feb 7 09:54:47 GMT 2011

> Hi,
> Am interested in using the OS OpenData contour set for an augmented 
> reality app for walkers (extension of the OpenTrailView idea). What I have 
> in mind is to load them into a database and implement a lookup facility 
> where the elevation at a particular lat/lon can be obtained by querying 
> the dataset. I believe the OS contours are rather higher precision than 
> SRTM, hence my interest in them, but to potentially save effort, has 
> anyone done something like this already?
I've done this, but on my own computer only, for hill panoramas.

The program I wrote is very crude but basically follows the following 

* Convert the OS contours into a regular grid of heights - just like the 
SRTM data
* From the current position - split the 360º panorama into half-degree 
* Using the grid - work out the height of each segment at, say, 200m 
distance intervals.
* Do a coordinate transform from x,y,z -> distance, altitude, azimuth.
* Hide points that cannot physically be seen (because a nearer point on that 
azumuth has a higher altitude)
* Plot the altitude & azimuth into a bmp file - shade points at different 
distances to give some depth perception.

I could upload a couple of examples to the wiki if you like.


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