You may wish to review the steps taken in GeoServer to use the GeoTools
renderer for objects that are over the dateline. I have not been able to
keep up but there have been a lot of improvements recently especially on
the raster rendering side of things.
Jody Garnett
On Tue, Jul 15, 2014 at 11:46 AM, Jack Orenstein <j...@geophile.com> wrote:
> I have a very basic question about the OGC SFA model. My apologies if this
> is the wrong forum to discuss this question, (any suggestions for
> alternatives?).
>
> Suppose you have a POLYGON that straddles the +/- 180 degree longitude.
> From my reading of the SFA spec, line segments are contained within the
> plane and there is no concept of wraparound. So I would represent this
> polygon as a MultiPolygon with two components, splitting the polygon at 180.
>
> Most operations on such a polygon should work correctly, but I think there
> at least a couple of problems. One possible problem is that NumGeometries()
> function is arguably wrong. I have a single polygon (the abstract one that
> wraps around 180), but I was forced to split it into two pieces. Also,
> Envelope() seems wrong. The definition of this function says:
>
> The minimum bounding box for this Geometry, returned as a Geometry. The
> polygon is defined by the corner points of the bounding box [(MINX, MINY),
> (MAXX, MINY), (MAXX, MAXY), (MINX, MAXY), (MINX, MINY)]. ... The simplest
> representation of an Envelope is as two direct positions, one containing
> all the minimums, and another all the maximums. In some cases, this
> coordinate will be outside the range of validity for the Spatial Reference
> System.
>
>
> Ideally (I think) the Envelope() would also straddle 180. However, this
> won't happen, given the dependence on MINX and MAXX, and it is even
> possible that the polygon and its Envelope() would be disjoint!
>
> I’d appreciate any thoughts on how to represent objects that straddle 180.
> Am I barking up the wrong tree?
>
> Jack Orenstein
>
>
>
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