[postgis-devel] ST_Length, ST_Length3d_spheroid

[Mark Cave-Ayland]

Paragon Corporation wrote:

> In writing the PostGIS  in Action book, this inconsistency is really bugging
> us.  I suppose changing this could break some apps.
> 
> We have ST_Length -- which is an alias for ST_Lenth2D and we have
> ST_Length3D.
> 
> We have ST_Length_Spheroid (which does a 3d length and is an alias for
> ST_Length_Spheroid3D exists) and we have ST_Length_Spheroid2D.
> Also observe we have no ST_Length_Sphere* (seems like it should mirror the
> ST_Distance_Sphere*).
> 
> So the main annoying inconsistency here is that ST_Length does a 2D length
> while ST_Length_Spheroid does a 3D length.  Can we just have both do a 3D
> length?
> 
> Thanks,
> Leo and Regina

That does seem terribly inconsistent. Given that the OGC spec only 
covers 2D, I'd expect that if people went out of their way to add 3 
dimensions or more then they would expect 3D lengths (otherwise they 
could simply wrap with a force_2d() function).


ATB,

Mark.

-- 
Mark Cave-Ayland - Senior Technical Architect
PostgreSQL - PostGIS
Sirius Corporation plc - control through freedom
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