On 8/01/2016 3:32 AM, Christoph Hormann wrote:
On Thursday 07 January 2016, Aaron Spaulding wrote:
Hi all,
I’ve been working on generating 3D meshes based on OSM data and I ran
into a problem. Vertical features like 'natural=cliff',
'barrier=retaining_wall’ and 'waterway=waterfall' occupy two points
in physical space, but because of the 2D nature of OSM its ambiguous
which side of the feature that the ‘ele’ tag applies.
For cliffs mapping conventions say that you should put the line on top
of the cliff in case it is not exactly vertical - accordingly the ele
tag would also refer to the top - but keep in mind that the elevation
does not have to be constant.
Consider who is going to use the map, and for what purpose.
The most critical use is for aeroplanes .. where the maximum height is
critical information!
I think for that reason alone most maps should indicate the maximum
elevation of an object.
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