[postgis-users] Problems with GeomUnion

Thu Apr 7 16:03:09 PDT 2005

Hi everyone,

I'm fairly new to PostGIS (and Mapserver), but have made amazing progress.  
Thanks for the great software!

I'm getting an error from GeomUnion that I don't understand.  I was 
getting the segfault from  rc3, and that was fixed with rc6.  Now, I get a 
different problem.

Some background: I'm displaying parcels.  I'd like go display 
subdivisions, but don't have the shapefiles for that.  So I loaded the 
parcels and their subdivision id and tried to create union objects of each 
subdivision.  Seemed sane to me.

Anyway, I tried to run this command:

select geomunion(parcel_shape) from parcels join parcel_info on sdf_id =
feat_num join subdivisions on subdivision = subdiv_id where subdiv_name
ilike 'FAIRWAY EST%';

That should have grabbed all of the parcels in my (old) neighborhood and 
created a union.  However, I got this:

NOTICE:  AssertionFailedException: EdgeRing::computePoints: found null Directed Edge
ERROR:  GEOS union() threw an error!

So, I tried a manual binary search to try to figure out where it was
failing, and it fails when you add the 38th parcel.  Interestingly, it 
allows the 37th and 38th to union, but not the whole set.

I have a picture of the shapes available at 
http://www/binko.net/unionfails.png

The blue outlines are all of the parcels that should be added (using the 
above query), the yellow is the union of the first 37 shapes, and the red 
is the 38th that blows it up.

I have WKT for all of this if anyone wants it, but I thought I'd just post 
the two shapes for now.  They are below...

Can anyone explain this to me?  I am using GEOM 2.1.1 if that matters.

Thanks
Bill

The Union of the first 37 is:

MULTIPOLYGON(((249504.223108452 1350036.44650513,249504.218689097 1350035.75305862,249514.770020721 1350146.64176436,249605.824741172 1350145.36811784,249694.42281974 1350144.80380146,249785.481952678 1350144.22401776,249876.541082203 1350143.64444507,249875.839443983 1350033.38646578,249863.52970887 1350032.77132712,249784.780058972 1350033.96603434,249772.474736413 1350034.0443706,249696.181735147 1350034.5301414,249681.415347528 1350034.62417867,249605.122343401 1350035.11012626,249590.355955228 1350035.20419774,249504.223108452 1350036.44650513)),((250721.354794677 1349856.03350435,250876.402472383 1349855.05050803,250878.859151544 1349854.34146378,250883.772510116 1349852.92337575,250886.224794653 1349851.52088592,250891.13375903 1349849.40935277,250896.033934518 1349845.91092814,250898.46864128 1349841.73465488,250900.898953963 1349836.86493574,250903.329267264 1349831.99521676,250903.302899868 1349827.83454048,250903.272137919 1349822.98041815,250903.241375983 1349818.12629583,250900.753931912 1349813.98121616,250898.262092682 1349809.14269061,250860.941571121 1349745.57962418,250831.070123231 1349692.37147928,250811.100096807 1349648.11574527,250801.066708383 1349618.35997578,250786.00560736 1349571.99271135,250778.398103289 1349536.67377626,250770.799380099 1349502.74173483,250768.219570749 1349484.03429748,250760.69557731 1349461.89084005,250753.206751931 1349445.29495194,250745.717920435 1349428.69906523,250735.772378028 1349412.81223226,250725.844417649 1349399.69918564,250713.446551616 1349385.21485722,250701.06626813 1349373.5043165,250606.117100466 1349537.07298432,250692.255405091 1349536.52656289,250692.976703749 1349650.25171378,250720.659947385 1349746.46902186,250721.354794677 1349856.03350435)),((250056.19386402 1350141.80813626,250144.79192773 1350141.24483528,250146.552106386 1350030.9712239,250136.707849632 1350031.03380197,250055.492729909 1350031.55016514,250056.19386402 1350141.80813626)),((250326.209785113 1350029.82960729,250318.826593097 1350029.87650686,250235.15041536 1350030.40813224,250235.851045406 1350140.66609521,250324.449102574 1350140.10319928,250415.503810199 1350138.83142923,250414.808087548 1350029.26692067,250414.803684262 1350028.57347443,250409.881556347 1350028.60472955,250326.209785113 1350029.82960729)),((251004.777048389 1350305.6886013,251024.465414498 1350305.56387938,251154.900835941 1350304.73784583,251147.350860283 1350278.4336388,251139.814046926 1350254.20977158,251129.785439018 1350225.14736601,251117.286982538 1350194.71365441,251023.76698331 1350195.30594458,250935.173480186 1350196.56071303,250933.411114204 1350306.83424711,251004.777048389 1350305.6886013)),((249314.550749715 1349625.03830099,249317.303722578 1349670.79007084,249320.109760215 1349724.86319918,249457.873029134 1349714.96968787,249454.859439956 1349628.30457303,249454.819659819 1349622.06355542,249454.788719727 1349617.20943062,249456.900634137 1349562.41147885,249459.193772503 1349536.04482979,249466.294196689 1349491.61720332,249473.40347786 1349448.57647199,249475.780607987 1349435.38530598,249485.368694378 1349395.10267833,249494.983316835 1349358.98073201,249502.207553088 1349333.96961334,249514.300994013 1349300.60577505,249523.986366857 1349275.57897884,249550.625626416 1349207.44875054,249560.364062321 1349190.74332026,249436.875009482 1349123.56976413,249419.868174717 1349158.35189331,249400.475406081 1349204.93830777,249393.184893934 1349219.54775013,249378.665782716 1349258.47488802,249361.800549086 1349315.44732959,249342.531744811 1349381.45027711,249335.378371309 1349417.5565701,249323.537188634 1349490.4469138,249321.257404221 1349518.89391151,249316.644778369 1349567.46655141,249314.550749715 1349625.03830099)),((250367.865922117 1349225.82852954,250261.698777412 1349173.10538217,250155.504897825 1349116.22183987,250094.633727443 1349219.93641492,250156.364344955 1349251.44382551,250200.818611665 1349275.43289868,250309.446679245 1349328.14024637,250367.865922117 1349225.82852954)),((250508.519136495 1349283.18737851,250424.630047574 1349250.433155,250363.749591895 1349352.76041557,250447.642922332 1349386.20795282,250477.255405199 1349398.50249939,250487.12622859 1349402.60068646,250590.743347274 1349441.47112175,250651.619839344 1349338.45077321,250629.403890577 1349328.18959412,250538.127274725 1349294.78852573,250508.519136495 1349283.18737851)),((249938.99678037 1349128.69410222,249993.344313592 1349160.2482303,250042.756296304 1349189.75339236,250103.627381696 1349086.03873623,250054.20650098 1349055.14660486,250002.311184103 1349022.18984776,249903.420491186 1348952.77798796,249842.562944875 1349058.57329412,249938.99678037 1349128.69410222)),((250003.846216674 1348876.55052383,250040.930819826 1348902.6667176,250078.006555984 1348927.39605345,250152.153479619 1348976.16138164,250194.151332356 1349000.85954014,250255.904231276 1349035.83434018,250310.22960004 1349063.92167233,250364.546082341 1349090.62218613,250446.00965892 1349128.93948004,250485.493220485 1349145.33221613,250527.446668013 1349163.09626397,250611.331449342 1349195.15726202,250643.396336637 1349206.0494291,250653.258391801 1349208.76076636,250663.120445539 1349211.47210607,250672.973701217 1349212.79655635,250682.818159884 1349212.7341172,250692.662618506 1349212.67168051,250702.502679299 1349211.91580036,250712.333945157 1349209.77303082,250722.165212025 1349207.63026377,250731.983288088 1349203.40716143,250739.344647914 1349199.89311336,250749.153933732 1349194.28312358,250756.506503078 1349189.38218698,250763.854677542 1349183.78780591,250766.293810637 1349180.30497209,250771.194060956 1349176.80653446,250776.072329766 1349169.84086796,250783.402925294 1349161.47270714,250788.27680197 1349153.81359639,250793.141888263 1349144.76759454,250795.545857524 1349135.73719561,250807.675618483 1349107.92135083,250714.051873621 1349092.56506397,250701.728671903 1349089.86931906,250652.453441517 1349081.86016138,250612.987488786 1349068.24104184,250593.245702515 1349060.04460488,250573.499507795 1349051.15473175,250526.623712617 1349033.42187106,250509.347417619 1349025.90330257,250494.532242939 1349018.36912048,250442.698896175 1348995.12003305,250430.353630686 1348988.95714247,250415.542829077 1348982.11643555,250358.751893736 1348953.35114133,250341.466721813 1348944.44575342,250314.301775812 1348930.05533266,250277.252627998 1348909.48645314,250247.60887573 1348892.33792818,250215.490742136 1348873.12472537,250195.726737932 1348861.46125471,250171.00959675 1348844.97495362,250143.822480256 1348827.11741835,250119.109703171 1348811.32459513,250096.862455882 1348796.20958743,250072.140822705 1348779.02990109,250042.474834139 1348758.41429751,250027.633009166 1348746.71961193,250002.902494353 1348728.15307609,249965.795651768 1348698.56968577,249936.103079669 1348673.79348449,249851.995984091 1348607.06159612,249766.398526226 1348692.90367627,249860.398707315 1348767.20064693,249895.035603672 1348795.41270496,249909.877451662 1348807.10734118,249929.668038929 1348822.93134666,250003.846216674 1348876.55052383)),((249699.080293261 1348943.67643334,249793.088850917 1349019.36013223,249853.959568578 1348915.64508782,249814.378405604 1348883.99716233,249772.322798097 1348850.28460327,249757.480923536 1348838.59001822,249690.69017056 1348785.61772999,249607.550177841 1348870.75106162,249699.080293261 1348943.67643334)))

and the 38th is:

MULTIPOLYGON(((249426.171937159 1350147.20648582,249514.770020721 1350146.64176436,249504.218689097 1350035.75305862,249386.091997729 1350037.19953568,249426.171937159 1350147.20648582)))