[Talk-GB] OS OpenData contours

Phil Endecott spam_from_osmgb at chezphil.org
Mon Feb 7 11:48:50 GMT 2011


Hi Nick,

Nick Whitelegg wrote:
> 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 believe you've asked me about this before, and I have code to parse 
the gridded version of this data and to create binary files from it, 
similar to the ".hgt" files that SRTM is distributed in.  The total 
size is about 60 MB in about 13,000 gzipped files, one per 5km square, 
with a 50m horizontal resolution.  Trivial interpolation within the 
grid seems to work pretty well compared to OS spot heights e.g. within 
5m on summits, which is much better than I get using SRTM.  I also have 
a version that is downsampled to a 200m grid which is of course much 
smaller.  Lookups are quite straightforward once you have converted 
your lat/lon to eastings and northings.

You are welcome to take a copy of this data, if you would like it.


Regards,  Phil.






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