[postgis-users] ST_Intersection returning offset point on two lines which intersect

[David Campbell]

Hi,

I have two lines which intersect but ST_Intersection returns an offset
point. Offset is around 0.000026m.

WITH line1 AS (SELECT ST_GeomFromText('LINESTRING(470874.945140537
6000126.53834916,470825.026548551 6000129.39039651,470813.970641131
6000131.67770864,470798.339625488 6000130.91512638,470770.509325729
6000128.62757298,470716.373201037 6000122.90909733,470592.358279565
6000112.18733429,470584.082725689 6000111.4719529,470471.616772575
6000098.31957132,470442.261380633 6000108.99375658,470402.993405271
6000132.6307069,470339.326451592 6000140.06487686,470261.553382752
6000143.87732586,470226.86058284 6000141.9710548,470158.999734862
6000139.4932543,470075.507824541 6000123.86262835,470042.340010929
6000112.04367615,470005.359698272 6000095.84140767,469987.441344206
6000088.9789069,469981.323382904 6000088.34605401,469976.38532627
6000087.83546738,469928.191247079 6000074.51890886)') as the_geom),
     line2 AS (SELECT ST_GeomFromText('LINESTRING(470835.701330449
6000121.00308247,470835.612988186 6000125.16357655,470834.757333107
6000165.42524755,470834.681958091 6000168.96974537,470841.821713877
6000270.84345442,470838.892222296 6000668.7623786,470838.348652514
6000835.0334808)') as the_geom)SELECT
st_intersects(ST_Intersection(line1.the_geom,
line2.the_geom),line1.the_geom) FROM line1JOIN line2 ON true


https://gis.stackexchange.com/questions/359210/line-intersection-resulting-in-offset-point


I have just tried to introduce ST_SnapToGrid, but all attempts at syntax
still return false. in example:

WITH line1 AS (SELECT ST_SnapToGrid(the_geom, 0.001) the_geom FROM
(SELECT ST_GeomFromText('LINESTRING(470874.945140537
6000126.53834916,470825.026548551 6000129.39039651,470813.970641131
6000131.67770864,470798.339625488 6000130.91512638,470770.509325729
6000128.62757298,470716.373201037 6000122.90909733,470592.358279565
6000112.18733429,470584.082725689 6000111.4719529,470471.616772575
6000098.31957132,470442.261380633 6000108.99375658,470402.993405271
6000132.6307069,470339.326451592 6000140.06487686,470261.553382752
6000143.87732586,470226.86058284 6000141.9710548,470158.999734862
6000139.4932543,470075.507824541 6000123.86262835,470042.340010929
6000112.04367615,470005.359698272 6000095.84140767,469987.441344206
6000088.9789069,469981.323382904 6000088.34605401,469976.38532627
6000087.83546738,469928.191247079 6000074.51890886)') as the_geom) a),
     line2 AS (SELECT ST_SnapToGrid(the_geom, 0.001) the_geom FROM
(SELECT ST_GeomFromText('LINESTRING(470835.701330449
6000121.00308247,470835.612988186 6000125.16357655,470834.757333107
6000165.42524755,470834.681958091 6000168.96974537,470841.821713877
6000270.84345442,470838.892222296 6000668.7623786,470838.348652514
6000835.0334808)') as the_geom) a)SELECT
st_intersects(ST_SnapToGrid(ST_Intersection(line1.the_geom,
line2.the_geom), 0.001), line1.the_geom) FROM line1JOIN line2 ON true


how do I get this query to return true?


David
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