[postgis-devel] [PostGIS] #529: && operator doesn't work on Geography
PostGIS
trac at osgeo.org
Tue Jun 8 07:53:00 PDT 2010
#529: && operator doesn't work on Geography
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Reporter: torlan | Owner: pramsey
Type: defect | Status: closed
Priority: critical | Milestone: PostGIS 1.5.2
Component: postgis | Version: trunk
Resolution: invalid | Keywords:
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Changes (by pramsey):
* status: new => closed
* resolution: => invalid
Comment:
Your second bounding box is a narrow rectangle over the international
dateline, there are no world capitals in that box.
Your problem is a specific example of the general issue around describing
bounded areas and arcs on a sphere. Since lines are segments of great
circles, and coordinate pair has two interpretations, a short one and a
long one. As a design decision in PostGIS geography, we decided to always
choose the short one.
Microsoft made similar choices in their geography, but also added an
"everything" geography to get around the problem of defining a world-
covering region. It looks like your version of a world-covering entity did
in fact return the right results, but that is not be design: I never
tested that case, we just got lucky.
To create a region that covers large swathes of the globe, build it from
arcs that are less than 180 degrees apart. That way each arc will be
interpreted as the smaller possibility and the region as a whole will
bound the area you want.
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Ticket URL: <http://trac.osgeo.org/postgis/ticket/529#comment:1>
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