[postgis-users] inconsistent comparison with sql server 2008

[Jon Flitton]

Hello everyone

I've been trying to replicate some data in postgis that I have in sql server however the postgis version gives inconsistent results so I'm looking for help to see if I have something wrong.

So the data I am creating is to segment the globe in to 8 triangles. The nodes are then located at the poles and the 4 "corners" of the equator.
I am using the geography type in both databases and wgs84
Below I give the text version of the polygons (as they come out of the database using STAsText in sqlserver and ST_AsText in postgis)
Also sown is the area of the polygon which is a simple check on the polys.
In sql server I have
Text                                                                       Area
POLYGON ((0 0, 0 90, -90 0, 0 0))                63758201600773.2
POLYGON ((-90 0, 0 90, 180 0, -90 0))       63758199375051
POLYGON ((180 0, 0 90, 90 0, 180 0))        63758199375051
POLYGON ((90 0, 0 90, 0 0, 90 0))               63758201600773.2
POLYGON ((0 0, 0 -90, 90 0, 0 0))                63758201600773.2
POLYGON ((90 0, 0 -90, -180 0, 90 0))       63758208279862.1
POLYGON ((-180 0, 0 -90, -90 0, -180 0))  63758203826495.3
POLYGON ((-90 0, 0 -90, 0 0, -90 0))          63758201600773.2

In postgis
POLYGON((0 0,0 90,-90 0,0 0))

63758234549478.10

POLYGON((-90 0,0 90,180 0,-90 0))

63758234549482.70

POLYGON((180 0,0 90,90 0,180 0))

63758234549478.20

POLYGON((90 0,0 90,0 0,90 0))

148769213948756.00

POLYGON((0 0,0 -90,90 0,0 0))

NaN

POLYGON((90 0,0 -90,-180 0,90 0))

NaN

POLYGON((-180 0,0 -90,-90 0,-180 0))

NaN

POLYGON((-90 0,0 -90,0 0,-90 0))

NaN



So the first three in post gis are similar in area  (I assume a slightly different geoid is used) but the 4th one is very different and the southern hemisphere are all wrong.

Any ideas?


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20111026/5d07cfe5/attachment.html>