geography - PostGIS: ST_Intersects() between two geographies, sometimes returns false result -

geography - PostGIS: ST_Intersects() between two geographies, sometimes returns false result -

i have problem intersect between 2 geographies in postgis: have table1 geography-column, filled multi-polygons in wgs84 (one per line). sec table2 has geography-column filled multi-polygons in wgs84 (one per line). intersect (select (..) st_intersects()) between both.

in (very rare) cases seems me, doesn't work right because intersect returns false true expected: have reprojected tif representing geography 1 line in table1, covers big area in tanzania. have reprojected tif 1 line in table2, covers little area of km². in arcmap, both intersect, little area on border of big, postgis returns false st_intsersects(geog1, geog2).

when export table1 shapefile via dumper, corner-points of geography connected direct lines, not parts of big circles. same result: area table2 outside area table1. guess, postgis calculates simplified polygon, far understood geography meant calculate parts of big circles instead of direct lines ?

i tried ensure both tables filled geography , not geometry, explicit cast geography didn't alter results.

did happen before or have thought did wrong ? problem table2 has geometry , raster-column (=3 spatial columns alltogether) ?

without seeing actual geometries, cannot certain, misinterpreting how great circle lines bound area, , postgis getting right, particularly if you're dealing relationships near boundaries. using google earth line strings (not polygons, not rendered using great circles) visualize examples can helpful in clarifying how things working visually.

postgis geography intersect