[postgis-devel] ST_ShiftLongitude

[strk]

Another thing... 
for very good results the "cut" operation should
really ST_SplitGeometry and "glue" operation should
ST_Union.

If we ST_Union w/out ST_Split we'll loose symmetricity
so I'd avoid that for the moment. One can always
ST_Union manually later..

--strk;

On Tue, Feb 23, 2010 at 04:25:31PM +0100, strk wrote:
> On Tue, Feb 23, 2010 at 03:08:05PM +0100, strk wrote:
> 
> > So, what I think should be paremetrized is:
> > 	1: X-value for where to cut (longitude)
> > 	2: Side to move (left to right or right to left)
> > 	3: range of the whole block
> > 	   (minx if moving right to left, maxx if moving left to right)
> 
> I'm thinking the parameter could be reduced to 2:
> 
> 	1: X-value representing the cut-line
> 	2: shift amount
> 
> If shift amount is negative we're moving left
> if it's positive we're moving right.
> 
> The function should check component geometries of a feature
> to fall *completely* on the left (moving right) or right (moving left)
> of the given X-value and only move those. Doing so will avoid introducing
> invalid geometries.
> 
> The function would not be symmetric anymore.
> Going from -180..180 to 0..360 would be done with:
> 	ST_ShiftLongitude(the_geom, 0, +360)
> Going from 0..360 to -180..180 would be done with:
> 	ST_ShiftLongitude(the_geom, 180, -360)
> 
> How do you like it ?
> If we want to keep the same function (would be easier) this
> would mean taking no args as a default of 0, +360 and loosing
> the current symmetricity (which again is not documented).
> 
> --strk; 
> 
>   ()   Free GIS & Flash consultant/developer
>   /\   http://foo.keybit.net/~strk/services.html
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