[Talk-GB] OS OpenData contours

[Nick Whitelegg]

Hello Phil,

>> 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.

Yes, could be useful, thanks. Sorry - what I thought I asked about last time was about VectorMap District data. No great urgency - just thought I'd raise it now as the OpenDEM post on the talk list reminded me about it.

Nick

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