[OSM-dev] SRTM Contour generation and height labelling

[Artem Pavlenko]

Nick,

You can use segment merging code from osm2pgsql.c (or osm2sql.py). Also, JTS 
and GEOS both should to the trick.  I suggest you get a copy of JUMP (JTS 
gui) and play with your shapefiles.
Something like this might work (untested:)
1. load shape file
2. run 'union' on segments with the same height
3. split MultiLineStrings into LineStrings
3. export to shapefile

Also, why don't you create one big shapefile for the whole country + index 
file?  
Cheers
Artem

On Sunday 11 February 2007 10:37, Nick Whitelegg wrote:
> Hello everyone,
>
> I have something of a problem with height labelling on SRTM contours using
> Mapnik. The problem is that because the contours are generated by working
> out intersection points in each grid square within the SRTM height file
> (grid square are 1/120 degree across) the contour polylines in the
> generated shapefile are too short to be labelled in Mapnik. That is, each
> contour polyline in the shapefile only spans one 1/120 degree grid square.
>
> As well as my own utility (described above), the GDAL utility,
> gdal_contour, also results in contours which are not labelled frequently
> enough.
>
> Looking at it, it seems that it will be very complex to write code from
> scratch to be able to define individual contour lines which cross multiple
> 1/120 degree grid squares (e.g. treat the 500ft contour surrounding a 3km
> radius hill as a single polyline in a shapefile). Can anyone provide any
> pointers, maybe to existing code to solve this problem?
>
> Thanks,
> Nick
>
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