Dear List,
This may be slightly ‘off-topic’, if so perhaps someone could suggest a more appropriate forum.
I have been using MapInfo EasyLoader facility to upload MapInfo tables to Oracle Spatial.
The tables uploaded are Lat/Long GDA94 and when opened via MapInfo, report that coordinate system.
I now want to work out how to do overlap analyses on the data in Oracle Spatial using SQL+.
I have come up with the following query that returns the the ID’s and overlap area of polygons from table A that overlap with a polygon in table B:
SELECT A.PolyID, SDO_GEOM.SDO_AREA(SDO_GEOM.SDO_INTERSECTION(A.GEOLOC, B.GEOLOC, 0.005), 0.005)
FROM TableA A, TableB B
WHERE B.PolyID = 'ID999'
AND SDO_RELATE(A.GEOLOC, B.GEOLOC, 'mask = OVERLAPBDYINTERSECT querytype=WINDOW') = 'TRUE'
The return is something like:
PolyID Overlap Area
-------- --------------
ID1 123.45
ID2 678.90
This seems ok, but the areas given are different by a constant factor from the areas that a similar query run in MapInfo return.
It looks like the areas given may be ‘Cartesian’.
Does anyone have any clues at to how to get the ‘correct’ areas out of the SQL+ query?
Does it by any chance have anything to do with a SRID value in the Oracle data?
Thanks and best regards.
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