[OSM-dev] Altitude data & (cycle) route profiles

MilesTogoe miles.togoe at gmail.com
Sat Mar 29 13:14:39 GMT 2008


Frederik Ramm wrote:
> Hi,
>
>   
>> I was thinking about adding nodes to long ways. This may sound a bit
>> ugly at first, but not if you consider the fact that the SRTM actually
>> provides real information about these points along long ways. It is
>> just that the latitude and longitude are not reliable, only the
>> altitude is.
>>     
>
> Doesn't sound very good to me, adding nodes to existing ways just to
> import height... I'd rather have the height as a separate info. Much
> like a road that enters a forest; I don't put a node at that point
> just to say that this node represents the road entering the forest - I
> just model the forest as an extra entity and whoever needs to can
> compute the point.
>
> Also, having SRTM data as nodes in OSM touches on the often discussed
> topic of immutable data. Would it be ok for people to edit individual
> SRTM nodes? 
>
> I'd also recommend to first do an analysis about the impact on OSM
> altogether, i.e. by how much would the planet file grow by importing
> SRTM data like you suggest? If renderers would start to use that
> information, then we'd suddenly have not a single "empty" tile
> anymore, every land tile on the planet would have information on it
> (right?), how would taht impact storage requirements for tile servers
> etc.? - Not saying that any of these could be a show-stopper, it's
> just that such an analysis should be part of the plan.
>   
Actually the vertical inflection points (bottom, change, or top of 
vertical curve) along a way are very useful points to have even if they 
are along a tangent section.   The inflection points are used for sight 
distance, drainage issues, calculation of grade or steepness, 
calculation of traveled distance, etc.  Each node and inflection point 
should have the lat, long, and elevation.  A straight line but up and 
down way will have a greater travel distance than a flat way.  As a 
civil engineer, I've always thought 2-D points are lacking and should 
always be 3-D points.   Is it more storage, processing/retrieval cost ?  
Sure, but it's important data. 






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