[OSM-dev] shortest streets

Lennard ldp at xs4all.nl
Thu Sep 17 10:54:42 BST 2009


Stephan Knauss wrote:

> So could you specify a better projection that would be equidistant? The 
> data here uses 900913.
> Would 4326 be equidistant?

FWIW, this is what I'm using on my cycle map:

ST_length_spheroid(transform(way,4326),'SPHEROID["WGS 
84",6378137,298.257223563,AUTHORITY["EPSG","7030"]]')

Note the space in "WGS 84".

> Is there a difference between st_length() and length()? They both return 
> the same values (at least for 900913).

Same thing, but the ST_ is the newer version, thought up to distinguih 
spatial calls.

> Postgis manual has a similar query to sum up the length of ways. Why is 
> it working there? Different projection?

I guess it's just an example of the ST_length() function as is, not 
taking into account any projection issues.


-- 
Lennard




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