[postgis-tickets] [PostGIS] #2786: st_buildArea returns null geom

PostGIS trac at osgeo.org
Thu Jun 26 06:40:15 PDT 2014 

#2786: st_buildArea returns null geom
---------------------+------------------------------------------------------
 Reporter:  mjurce   |       Owner:  pramsey
     Type:  defect   |      Status:  new    
 Priority:  medium   |   Milestone:         
Component:  postgis  |     Version:  2.0.x  
 Keywords:           |  
---------------------+------------------------------------------------------
Changes (by robe):

  * priority:  blocker => medium


Comment:

 I'm not sure there is an issue here.  Result seems to be a cause of
 rounding effects which makes the generated polygon invalid.  Just to get
 to the point, your example can be reduced to:


 {{{
 SELECT ST_LineMerge(st_curvetoline(st_GeomFromText('MULTICURVE((715537.187
 91770.539,715541.774 91782.060,715552.413 91787.648,715554.587
 91795.922,715557.280 91801.092,715557.152 91795.643,715559.827
 91794.284,715580.191 91814.057,715584.102 91815.280,715607.318
 91826.989,715609.459 91829.830,715609.588 91839.660,715606.190
 91837.710,715603.506 91837.322,715599.678 91834.403,715593.014
 91831.325,715592.151 91830.889,715588.161 91831.919,715584.211
 91834.084,715580.055 91837.074,715575.738 91839.398,715571.882
 91841.719,715569.010 91842.588,715562.923 91844.881,715551.009
 91847.220,715541.481 91845.339,715538.953 91842.280,715528.604
 91842.106,715527.956 91846.181,715525.549 91849.393,715525.717
 91849.515,715516.818 91860.240,715505.961 91849.502,715501.797
 91845.422,715491.018 91834.644,715479.196 91810.681,715477.609
 91812.014,715446.445 91826.586,715445.016 91827.461,715443.889
 91828.677,715443.198 91830.216,715443.020 91831.896,715443.345
 91833.529,715438.564 91830.984,715437.963 91829.340,715432.470
 91814.247,715423.645 91818.572,715416.744 91810.214,715417.434
 91810.007,715412.152 91802.380,715411.587 91794.394,715411.386
 91791.554,715411.378 91783.632,715411.425 91782.252,715411.638
 91777.893,715413.585 91771.282,715408.214 91770.716,715406.827
 91770.484,715401.043 91769.483,715391.406 91767.254,715378.023
 91762.959,715377.340 91762.528,715376.939 91761.826,715369.312
 91760.180,715370.885 91759.433,715372.130 91757.782,715372.655
 91755.781,715373.354 91720.501,715370.178 91721.285,715368.303
 91705.398,715365.812 91705.458,715365.203 91699.854,715377.986
 91699.243,715379.798 91688.574,715382.266 91682.528,715382.283
 91684.028,715382.403 91688.324,715384.534 91695.865,715388.055
 91701.887,715395.704 91714.939),CIRCULARSTRING(715395.704
 91714.939,715395.742 91715.167,715395.679 91715.389),(715395.679
 91715.389,715395.186 91716.412),CIRCULARSTRING(715395.186
 91716.412,715394.911 91716.841,715394.579
 91717.227),CIRCULARSTRING(715394.579 91717.227,715394.199
 91717.561,715393.776 91717.838),CIRCULARSTRING(715393.776
 91717.838,715393.310 91718.057,715392.808
 91718.172),CIRCULARSTRING(715392.808 91718.172,715392.532
 91718.189,715392.255 91718.174),(715392.255 91718.174,715405.385
 91719.053,715417.385 91719.739,715436.177 91720.812,715440.093
 91720.705,715444.376 91719.881,715446.928 91718.899,715448.936
 91718.127,715453.889 91715.987),CIRCULARSTRING(715453.889
 91715.987,715453.301 91717.020,715452.497 91717.896),(715452.497
 91717.896,715453.751 91717.354,715460.889 91714.267,715464.984
 91712.969,715469.019 91712.225,715473.079 91711.950,715488.666
 91711.014,715488.704 91715.333,715472.950 91716.313,715475.197
 91719.457,715480.797 91727.668,715484.038 91732.282,715485.594
 91731.384,715488.190 91729.587,715486.780 91726.930,715495.235
 91720.858,715508.002 91712.134,715514.139 91709.249,715521.129
 91710.293,715521.337 91711.690,715524.085 91719.505,715525.492
 91722.476,715531.480 91720.161,715536.262 91728.232,715527.955
 91736.355,715533.632 91752.179,715536.527 91767.968,715537.187
 91770.539))')) );
 }}}

 which gives you a seemingly nice looking closed linestring which we can
 use our lazy ST_MakePolygon to build a polygon out of:

 {{{
 SELECT ST_MakePolygon('LINESTRING(715392.255 91718.174,715405.385
 91719.053,715417.385 91719.739,715436.177 91720.812,715440.093
 91720.705,715444.376 91719.881,715446.928 91718.899,715448.936
 91718.127,715453.889 91715.987,715453.780829874
 91716.2231798697,715453.661201247 91716.4537675939,715453.530402315
 91716.6782076665,715453.388748183 91716.8959593919,715453.236580109
 91717.1064981869,715453.074264679 91717.3093168453,715452.902192926
 91717.503926759,715452.720779384 91717.6898590959,715452.530461096
 91717.8666659285,715452.497 91717.896,715453.751 91717.354,715460.889
 91714.267,715464.984 91712.969,715469.019 91712.225,715473.079
 91711.95,715488.666 91711.014,715488.704 91715.333,715472.95
 91716.313,715475.197 91719.457,715480.797 91727.668,715484.038
 91732.282,715485.594 91731.384,715488.19 91729.587,715486.78
 91726.93,715495.235 91720.858,715508.002 91712.134,715514.139
 91709.249,715521.129 91710.293,715521.337 91711.69,715524.085
 91719.505,715525.492 91722.476,715531.48 91720.161,715536.262
 91728.232,715527.955 91736.355,715533.632 91752.179,715536.527
 91767.968,715537.187 91770.539,715541.774 91782.06,715552.413
 91787.648,715554.587 91795.922,715557.28 91801.092,715557.152
 91795.643,715559.827 91794.284,715580.191 91814.057,715584.102
 91815.28,715607.318 91826.989,715609.459 91829.83,715609.588
 91839.66,715606.19 91837.71,715603.506 91837.322,715599.678
 91834.403,715593.014 91831.325,715592.151 91830.889,715588.161
 91831.919,715584.211 91834.084,715580.055 91837.074,715575.738
 91839.398,715571.882 91841.719,715569.01 91842.588,715562.923
 91844.881,715551.009 91847.22,715541.481 91845.339,715538.953
 91842.28,715528.604 91842.106,715527.956 91846.181,715525.549
 91849.393,715525.717 91849.515,715516.818 91860.24,715505.961
 91849.502,715501.797 91845.422,715491.018 91834.644,715479.196
 91810.681,715477.609 91812.014,715446.445 91826.586,715445.016
 91827.461,715443.889 91828.677,715443.198 91830.216,715443.02
 91831.896,715443.345 91833.529,715438.564 91830.984,715437.963
 91829.34,715432.47 91814.247,715423.645 91818.572,715416.744
 91810.214,715417.434 91810.007,715412.152 91802.38,715411.587
 91794.394,715411.386 91791.554,715411.378 91783.632,715411.425
 91782.252,715411.638 91777.893,715413.585 91771.282,715408.214
 91770.716,715406.827 91770.484,715401.043 91769.483,715391.406
 91767.254,715378.023 91762.959,715377.34 91762.528,715376.939
 91761.826,715369.312 91760.18,715370.885 91759.433,715372.13
 91757.782,715372.655 91755.781,715373.354 91720.501,715370.178
 91721.285,715368.303 91705.398,715365.812 91705.458,715365.203
 91699.854,715377.986 91699.243,715379.798 91688.574,715382.266
 91682.528,715382.283 91684.028,715382.403 91688.324,715384.534
 91695.865,715388.055 91701.887,715395.704 91714.939,715395.713154168
 91714.9631954524,715395.721110095 91714.987810934,715395.727848615
 91715.0127871441,715395.733353493 91715.0380639127,715395.737611468
 91715.0635803459,715395.740612282 91715.0892749724,715395.742348705
 91715.1150858915,715395.742816556 91715.1409509225,715395.742014706
 91715.1668077543,715395.739945087 91715.1925940954,715395.736612685
 91715.2182478244,715395.732025529 91715.2437071392,715395.726194669
 91715.268910706,715395.719134151 91715.2937978073,715395.710860987
 91715.3183084878,715395.701395105 91715.3423836991,715395.690759311
 91715.3659654421,715395.679 91715.389,715395.186
 91716.412,715395.096710392 91716.5663712404,715394.9999537
 91716.7161753005,715394.895963018 91716.8610512891,715394.78498887
 91717.0006501874,715394.667298602 91717.1346356893,715394.579
 91717.227,715394.452401023 91717.3490657436,715394.319965057
 91717.4647725363,715394.182011154 91717.5738416303,715394.038871655
 91717.6760102686,715393.890891396 91717.7710323179,715393.776
 91717.838,715393.673467977 91717.8969548753,715393.568166681
 91717.9508077291,715393.460349789 91717.9994288249,715393.350277044
 91718.0427010304,715393.23821362 91718.0805200991,715393.124429488
 91718.1127949214,715393.009198763 91718.1394477445,715392.892799046
 91718.1604143594,715392.808 91718.172,715392.690809803
 91718.1831208597,715392.573215092 91718.1884780735,715392.455499164
 91718.1880587352,715392.337945605 91718.1818638553,715392.255
 91718.174)'::geometry);
 }}}

 Except for the tincy littly problem that the generated polygon is invalid
 even though it passes the quick spot check of being closed.


 {{{
 SELECT ST_IsValidReason(ST_MakePolygon('LINESTRING(715392.255
 91718.174,715405.385 91719.053,715417.385 91719.739,715436.177
 91720.812,715440.093 91720.705,715444.376 91719.881,715446.928
 91718.899,715448.936 91718.127,715453.889 91715.987,715453.780829874
 91716.2231798697,715453.661201247 91716.4537675939,715453.530402315
 91716.6782076665,715453.388748183 91716.8959593919,715453.236580109
 91717.1064981869,715453.074264679 91717.3093168453,715452.902192926
 91717.503926759,715452.720779384 91717.6898590959,715452.530461096
 91717.8666659285,715452.497 91717.896,715453.751 91717.354,715460.889
 91714.267,715464.984 91712.969,715469.019 91712.225,715473.079
 91711.95,715488.666 91711.014,715488.704 91715.333,715472.95
 91716.313,715475.197 91719.457,715480.797 91727.668,715484.038
 91732.282,715485.594 91731.384,715488.19 91729.587,715486.78
 91726.93,715495.235 91720.858,715508.002 91712.134,715514.139
 91709.249,715521.129 91710.293,715521.337 91711.69,715524.085
 91719.505,715525.492 91722.476,715531.48 91720.161,715536.262
 91728.232,715527.955 91736.355,715533.632 91752.179,715536.527
 91767.968,715537.187 91770.539,715541.774 91782.06,715552.413
 91787.648,715554.587 91795.922,715557.28 91801.092,715557.152
 91795.643,715559.827 91794.284,715580.191 91814.057,715584.102
 91815.28,715607.318 91826.989,715609.459 91829.83,715609.588
 91839.66,715606.19 91837.71,715603.506 91837.322,715599.678
 91834.403,715593.014 91831.325,715592.151 91830.889,715588.161
 91831.919,715584.211 91834.084,715580.055 91837.074,715575.738
 91839.398,715571.882 91841.719,715569.01 91842.588,715562.923
 91844.881,715551.009 91847.22,715541.481 91845.339,715538.953
 91842.28,715528.604 91842.106,715527.956 91846.181,715525.549
 91849.393,715525.717 91849.515,715516.818 91860.24,715505.961
 91849.502,715501.797 91845.422,715491.018 91834.644,715479.196
 91810.681,715477.609 91812.014,715446.445 91826.586,715445.016
 91827.461,715443.889 91828.677,715443.198 91830.216,715443.02
 91831.896,715443.345 91833.529,715438.564 91830.984,715437.963
 91829.34,715432.47 91814.247,715423.645 91818.572,715416.744
 91810.214,715417.434 91810.007,715412.152 91802.38,715411.587
 91794.394,715411.386 91791.554,715411.378 91783.632,715411.425
 91782.252,715411.638 91777.893,715413.585 91771.282,715408.214
 91770.716,715406.827 91770.484,715401.043 91769.483,715391.406
 91767.254,715378.023 91762.959,715377.34 91762.528,715376.939
 91761.826,715369.312 91760.18,715370.885 91759.433,715372.13
 91757.782,715372.655 91755.781,715373.354 91720.501,715370.178
 91721.285,715368.303 91705.398,715365.812 91705.458,715365.203
 91699.854,715377.986 91699.243,715379.798 91688.574,715382.266
 91682.528,715382.283 91684.028,715382.403 91688.324,715384.534
 91695.865,715388.055 91701.887,715395.704 91714.939,715395.713154168
 91714.9631954524,715395.721110095 91714.987810934,715395.727848615
 91715.0127871441,715395.733353493 91715.0380639127,715395.737611468
 91715.0635803459,715395.740612282 91715.0892749724,715395.742348705
 91715.1150858915,715395.742816556 91715.1409509225,715395.742014706
 91715.1668077543,715395.739945087 91715.1925940954,715395.736612685
 91715.2182478244,715395.732025529 91715.2437071392,715395.726194669
 91715.268910706,715395.719134151 91715.2937978073,715395.710860987
 91715.3183084878,715395.701395105 91715.3423836991,715395.690759311
 91715.3659654421,715395.679 91715.389,715395.186
 91716.412,715395.096710392 91716.5663712404,715394.9999537
 91716.7161753005,715394.895963018 91716.8610512891,715394.78498887
 91717.0006501874,715394.667298602 91717.1346356893,715394.579
 91717.227,715394.452401023 91717.3490657436,715394.319965057
 91717.4647725363,715394.182011154 91717.5738416303,715394.038871655
 91717.6760102686,715393.890891396 91717.7710323179,715393.776
 91717.838,715393.673467977 91717.8969548753,715393.568166681
 91717.9508077291,715393.460349789 91717.9994288249,715393.350277044
 91718.0427010304,715393.23821362 91718.0805200991,715393.124429488
 91718.1127949214,715393.009198763 91718.1394477445,715392.892799046
 91718.1604143594,715392.808 91718.172,715392.690809803
 91718.1831208597,715392.573215092 91718.1884780735,715392.455499164
 91718.1880587352,715392.337945605 91718.1818638553,715392.255
 91718.174)'::geometry));
 }}}

 Yields:

 {{{
 Self-intersection[715392.4655354 91718.1880944872]
 }}}

 So build area is fine, it will return NULL if the resulting polygon is
 invalid.  We can argue if ST_CurveToLine is at fault here and if anything
 can be done about it or if that's just what you get with floating
 precision issues.

 I think this might end up being a won't fix (I've downgrade from blocker
 to medium) but will leave that for others more knowledgeable to judge.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/2786#comment:1>
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