Sufficool, Stanley | 1 Dec 19:34 2008

RE: Arc catalog (Arc GIS) import

Before I get too far on this and run into a roadblock (legally or
technically), has anyone tried the Personal Geodatabase linked to a
PostgreSQL view?

My general plan is to create a view using a function to translate WKB to
the ESRI personal geodatabase format and then have an update trigger
take the submitted pgeo shapefile record from ArcMAP and translate it to
the geometry type for updating the underlying table.

> -----Original Message-----
> From: postgis-users-bounces <at> postgis.refractions.net 
> [mailto:postgis-users-bounces <at> postgis.refractions.net] On 
> Behalf Of Paragon Corporation
> Sent: Wednesday, November 26, 2008 6:32 PM
> To: 'PostGIS Users Discussion'
> Subject: RE: [postgis-users] Arc catalog (Arc GIS) import
> 
> 
> 
>  
> 
> 
> >  2. If you need to showcase some PostGIS functionality and people 
> > don't
> see an ESRI frontend, they tend to look at you like you have 
> three heads. 
> 
> Having 3 heads I imagine is more useful than having one 
> assuming they are not all fighting with each other :)
> 
(Continue reading)

Vincenzo Patruno | 2 Dec 12:04 2008
Picon

Postgres/PostGIS and date field

Hi list!

In my file .map I wrote something like

select the_geom .......... (end_date -  now() >= 10) as green and (end_date - now() < 0) as red .... from ....

The idea is using different coloured markers for expired points  or valid points

After upgrading Postgres/Gis with last available versions, the query above doesn't work anymore because 
I cannot compare date types with integers .......
Any idea?

Thanks in advance

Vinc
Mark Cave-Ayland | 2 Dec 12:16 2008
Picon

Re: Postgres/PostGIS and date field

Vincenzo Patruno wrote:

> Hi list!
> 
> In my file .map I wrote something like
> 
> 
> select the_geom .......... (end_date -  now() >= 10) as green and (end_date - now() < 0) as red .... from ....
> 
> 
> 
> The idea is using different coloured markers for expired points  or valid points
> 
> After upgrading Postgres/Gis with last available versions, the query above doesn't work anymore
because  I cannot compare date types with integers .......
> Any idea?
> 
> Thanks in advance
> 
> Vinc

Hi Vinc,

This sounds like the casting changes in 8.3 are hitting you here. Have 
you tried something like this:

select the_geom .......... (end_date -  now() >= '10 days'::interval) as 
green and (end_date - now() < '0'::interval) as red .... from ....

I'm not sure exactly what units you were using, but you should be able 
(Continue reading)

Picon

R: Postgres/PostGIS and date field

Maybe:
	select the_geom .......... 
		extract(day from (end_date -  now()) >= 10) as green 
		and extract(day from (end_date - now()) < 0) as red .... from ....

Bye
Paolo Rizzi

> -----Messaggio originale-----
> Da: postgis-users-bounces <at> postgis.refractions.net
> [mailto:postgis-users-bounces <at> postgis.refractions.net]Per 
> conto di Mark
> Cave-Ayland
> Inviato: martedì 2 dicembre 2008 12.17
> A: PostGIS Users Discussion
> Oggetto: Re: [postgis-users] Postgres/PostGIS and date field
> 
> 
> Vincenzo Patruno wrote:
> 
> > Hi list!
> > 
> > In my file .map I wrote something like
> > 
> > 
> > select the_geom .......... (end_date -  now() >= 10) as 
> green and (end_date - now() < 0) as red .... from ....
> > 
> > 
> > 
(Continue reading)

Randall, Eric | 2 Dec 23:27 2008

Exploding Polygons

Hi all,

I'm trying to figure out how to explode a set of polygons to display them with space between.  In my case they
are municipal boundary polys but could be anything.  So far the only approach I can think of is using
translate such that:

select st_translate(st_translate(poly, -x(st_centroid(poly)), -y(st_centroid(poly))),x(p2) +
(x(p2)- x(p1)), y(p2) + (y(p2) - y(p1)))
from 
(select st_centroid(st_collect(geom))as p1 from mypolytable) as s1,
(select st_centroid(geom) as p2, geom as poly from mypolytable) as s2

The problem with this is that small polys (Boroughs, etc) relative larger ones often don't get their own
space until a large enough multiplier is applied, i.e.   x(p2) + (x(p2)- x(p1))*5, y(p2) + (y(p2) - y(p1))*5
,  but then there is too much space around the larger polys.

Anyone have a suggestion or done this another way?  Thanks.

think i'm gonna splode...,

Eric 
Stephen Woodbridge | 2 Dec 23:43 2008

Re: Exploding Polygons

Randall, Eric wrote:
> Hi all,
> 
> I'm trying to figure out how to explode a set of polygons to display
> them with space between.  In my case they are municipal boundary
> polys but could be anything.  So far the only approach I can think of
> is using translate such that:
> 
> select st_translate(st_translate(poly, -x(st_centroid(poly)),
> -y(st_centroid(poly))),x(p2) + (x(p2)- x(p1)), y(p2) + (y(p2) -
> y(p1))) from (select st_centroid(st_collect(geom))as p1 from
> mypolytable) as s1, (select st_centroid(geom) as p2, geom as poly
> from mypolytable) as s2
> 
> 
> The problem with this is that small polys (Boroughs, etc) relative
> larger ones often don't get their own space until a large enough
> multiplier is applied, i.e.   x(p2) + (x(p2)- x(p1))*5, y(p2) +
> (y(p2) - y(p1))*5 ,  but then there is too much space around the
> larger polys.
> 
> Anyone have a suggestion or done this another way?  Thanks.
> 
> 
> 
> think i'm gonna splode...,

I'm not sure if it will work, but have you tried doing a buffer with a 
negative distance.

(Continue reading)

Carl Anderson | 3 Dec 02:45 2008

Re: Exploding Polygons

Have you considered subtracting a buffer around the boundary of each 
polygon from itself.  Kind of similar to st_buffer with a negative 
distance but a good bit more stable.

st_difference(geom,st_buffer(st_boundary(geom),100))) from mypolytable ;

st_buffer(geom,-X) will work until X gets large enough to start to get 
collapsing geometries and then you will get
    ERROR:  getPoint2d_p: point offset out of range

C.

Randall, Eric wrote:
> Hi all,
>
> I'm trying to figure out how to explode a set of polygons to display them with space between.  In my case they
are municipal boundary polys but could be anything.  So far the only approach I can think of is using
translate such that:
>
> select st_translate(st_translate(poly, -x(st_centroid(poly)), -y(st_centroid(poly))),x(p2) +
(x(p2)- x(p1)), y(p2) + (y(p2) - y(p1)))
> from 
> (select st_centroid(st_collect(geom))as p1 from mypolytable) as s1,
> (select st_centroid(geom) as p2, geom as poly from mypolytable) as s2
>
>
> The problem with this is that small polys (Boroughs, etc) relative larger ones often don't get their own
space until a large enough multiplier is applied, i.e.   x(p2) + (x(p2)- x(p1))*5, y(p2) + (y(p2) - y(p1))*5
,  but then there is too much space around the larger polys.
>
(Continue reading)

Aleš Kecman | 3 Dec 12:02 2008
Picon

Re: Get concave hull from an array of longitude in latitude points

Hi!

I'm still struggling with this "concave hulls" and it seems I just can't find the way how to do it. I'm sending a text file with some longitude and latitude points of selected subarea from which I need to get a concave polygon. There is only one polygon in attached text file. In my database I have around 500 000 points from which I need to form around 700 polygons. If there is a way to do it in PostGis I would really appreciate any help. I also attached a jpg picture of my convexhull polygon. Thanks!!!

Greets, Ales.



On Mon, Nov 24, 2008 at 12:13 PM, Mark Cave-Ayland <mark.cave-ayland <at> siriusit.co.uk> wrote:
Aleš Kecman wrote:
Hi!


I'm new to Postgis and would really like to get some help on getting a concave hull from an array of points.

For example:

I have an array of points - longitude and latitude of buildings in particular area in the city. I already managed to get a convex hull polygon from this array of points, but this is not really helpful. What I'm trying to get is some kind of concave hull polygon from an array of points, which I would further like to use in Google Earth kml file.

Thanks.


Hi Aleš,

Does ST_Union() help you at all?


ATB,

Mark.

--
Mark Cave-Ayland
Sirius Corporation - The Open Source Experts
http://www.siriusit.co.uk
T: +44 870 608 0063
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"Bled";14.0934013932;46.3584586261
"Bled";14.1078921815;46.3655453222
"Bled";14.0923049936;46.3571813412
"Bled";14.107332866;46.3647762075
"Bled";14.1058970676;46.364360122
"Bled";14.1047294095;46.363442283
"Bled";14.1039178791;46.3637958084
"Bled";14.1002130123;46.3622732029
"Bled";14.0998149264;46.3619821637
"Bled";14.0900279736;46.3565784333
"Bled";14.0993591037;46.3620415537
"Bled";14.0994031117;46.3617360002
"Bled";14.0997482029;46.3605061203
"Bled";14.0998444769;46.360182984
"Bled";14.0993846928;46.3596935221
"Bled";14.0992689349;46.3596206338
"Bled";14.0985708435;46.3593992029
"Bled";14.093913477;46.3581387907
"Bled";14.0945464193;46.3583687312
"Bled";14.0937107948;46.3578222871
"Bled";14.0928261935;46.3570955068
"Bled";14.1077921806;46.3708887894
"Bled";14.1073416663;46.3714160989
"Bled";14.1069909155;46.3714043632
"Bled";14.1071341669;46.3713874878
"Bled";14.1075579582;46.3709049557
"Bled";14.107257729;46.3709835855
"Bled";14.1068522103;46.3711423655
"Bled";14.1066303958;46.371194615
"Bled";14.1070732912;46.3711350951
"Bled";14.1069861843;46.3700997546
"Bled";14.1071526388;46.3702540042
"Bled";14.1064007202;46.3709319061
"Bled";14.1064661408;46.3709054262
"Bled";14.1119977119;46.3616185747
"Bled";14.1118896591;46.3610689149
"Bled";14.1118178384;46.3614912188
"Bled";14.1115994217;46.361336572
"Bled";14.111369471;46.3610918646
"Bled";14.1111535373;46.3607842862
"Bled";14.1109619881;46.3605758646
"Bled";14.1108222688;46.3603768429
"Bled";14.1109176019;46.3601076723
"Bled";14.113650747;46.3622611944
"Bled";14.1128579642;46.3622640434
"Bled";14.1125751541;46.3620729106
"Bled";14.1128782391;46.3618143478
"Bled";14.1123446132;46.3618641888
"Bled";14.1126471155;46.3616416103
"Bled";14.1124413983;46.3615050578
"Bled";14.1121714416;46.3613230208
"Bled";14.1138234517;46.3620286095
"Bled";14.1133585785;46.3618450646
"Bled";14.114661462;46.3616392305
"Bled";14.1136061911;46.361801999
"Bled";14.1149991585;46.3616508417
"Bled";14.1139070881;46.3616783724
"Bled";14.1152977281;46.3616711463
"Bled";14.1149921205;46.3612819078
"Bled";14.1151607498;46.361301207
"Bled";14.1156378926;46.3615298248
"Bled";14.1154866119;46.3612407488
"Bled";14.1159005276;46.3613609116
"Bled";14.1158723631;46.3614956497
"Bled";14.1160843276;46.3612453708
"Bled";14.1146302678;46.3603524094
"Bled";14.116075106;46.361011376
"Bled";14.114255634;46.360214552
"Bled";14.1160258877;46.3608400514
"Bled";14.1132111998;46.3605123568
"Bled";14.1159519883;46.3605875624
"Bled";14.1131945672;46.3607371544
"Bled";14.1157468473;46.360415032
"Bled";14.1128723459;46.3605727078
"Bled";14.1153856394;46.360250291
"Bled";14.1121023687;46.3607736638
"Bled";14.115100652;46.3601941035
"Bled";14.1117370873;46.3608607974
"Bled";14.1147511333;46.3601104245
"Bled";14.1144270214;46.3600629295
"Bled";14.1140636387;46.3600331234
"Bled";14.1135557272;46.3601011635
"Bled";14.1131913258;46.3601343261
"Bled";14.1131666488;46.3600531612
"Bled";14.1128904358;46.360257951
"Bled";14.1125387353;46.3603092043
"Bled";14.1122639757;46.3604240332
"Bled";14.1119378236;46.3605024741
"Bled";14.0816594482;46.3620177325
"Bled";14.0815851029;46.3618012059
"Bled";14.0809547412;46.3614182644
"Bled";14.0834561978;46.3594859798
"Bled";14.0846901864;46.3587401108
"Bled";14.0838855155;46.3586796843
"Bled";14.0873562116;46.3578347232
"Bled";14.0873768432;46.3573760374
"Bled";14.0874606407;46.3570258205
"Bled";14.0897660262;46.3574850523
"Bled";14.0870500101;46.3559338972
"Bled";14.0885279886;46.3569173719
"Bled";14.088675096;46.3566666265
"Bled";14.1233212467;46.3654037426
"Bled";14.1232123942;46.3657088077
"Bled";14.1231817982;46.3659964787
"Bled";14.1227793861;46.3659664011
"Bled";14.1229132234;46.3657245074
"Bled";14.12315077;46.3663111376
"Bled";14.1226072827;46.3661630158
"Bled";14.1193852288;46.3669029963
"Bled";14.1222577143;46.3660793595
"Bled";14.1189058539;46.366809333
"Bled";14.1208575809;46.3666714056
"Bled";14.1211522847;46.3669345855
"Bled";14.1204527106;46.3667942507
"Bled";14.1188886638;46.367070115
"Bled";14.120203925;46.3669092985
"Bled";14.1195697494;46.3675522048
"Bled";14.1193530216;46.3672896214
"Bled";14.1183242566;46.3666069149
"Bled";14.1189980996;46.3675388048
"Bled";14.1184732512;46.367039922
"Bled";14.1189553528;46.3677723987
"Bled";14.1182747043;46.3672633174
"Bled";14.118912461;46.3680149885
"Bled";14.1180504547;46.3674685202
"Bled";14.1175660066;46.3676897088
"Bled";14.1186608;46.3675002173
"Bled";14.1180448076;46.3678193615
"Bled";14.1184352482;46.3677863842
"Bled";14.1171983684;46.3679207943
"Bled";14.1182196494;46.3682615653
"Bled";14.1165272487;46.3676277054
"Bled";14.1168258515;46.3676480063
"Bled";14.1168733382;46.3679272815
"Bled";14.1167692299;46.3679354745
"Bled";14.1179233598;46.3680973332
"Bled";14.1170792353;46.3680548303
"Bled";14.1179063094;46.3683491191
"Bled";14.1167391787;46.3681871597
"Bled";14.1175848986;46.36813071
"Bled";14.1128018953;46.3657274747
"Bled";14.1135385442;46.3635738949
"Bled";14.113062084;46.3657114991
"Bled";14.1139413695;46.3635770171
"Bled";14.1133746887;46.3656689382
"Bled";14.1145081492;46.3654977803
"Bled";14.1136614487;46.365617179
"Bled";14.1139477718;46.3655924069
"Bled";14.1141519082;46.365827912
"Bled";14.1151196324;46.3654575287
"Bled";14.114451954;46.3657582596
"Bled";14.1151040227;46.3656193549
"Bled";14.1134627419;46.365849562
"Bled";14.1134972151;46.3661287379
"Bled";14.1143884889;46.3664685352
"Bled";14.1139741017;46.3663753545
"Bled";14.1144108443;46.3666936347
"Bled";14.1143004856;46.3670886501
"Bled";14.1146647011;46.367874214
"Bled";14.1221045368;46.3667169742
"Bled";14.1230972448;46.3672194292
"Bled";14.1217919325;46.366759559
"Bled";14.1225758498;46.367314397
"Bled";14.1187266184;46.3682564767
"Bled";14.1217931052;46.367497326
"Bled";14.1214150869;46.3675663985
"Bled";14.117268225;46.3684251684
"Bled";14.1208785254;46.3677961978
"Bled";14.1207488602;46.3677772067
"Bled";14.1161514805;46.3683625595
"Bled";14.1188605995;46.3688153262
"Bled";14.1154247486;46.3682939605
"Bled";14.117898344;46.3688438953
"Bled";14.1178200806;46.3688612856
"Bled";14.1175191526;46.3689849222
"Bled";14.1142698952;46.3681770562
"Bled";14.113607709;46.3681359367
"Bled";14.1169879252;46.3688818536
"Bled";14.1133748099;46.3680711517
"Bled";14.1168286426;46.3690875555
"Bled";14.1159121907;46.3686936004
"Bled";14.1155735795;46.3687359671
"Bled";14.1121327881;46.3677196266
"Bled";14.1150817809;46.3686062035
"Bled";14.1148244855;46.3684422652
"Bled";14.1121895795;46.3674231649
"Bled";14.1135242058;46.3684771772
"Bled";14.1112277835;46.3674246903
"Bled";14.1133702974;46.3683500253
"Bled";14.1109709432;46.3672337556
"Bled";14.1121650691;46.3681337415
"Bled";14.1105824007;46.3671497605
"Bled";14.1111222234;46.3683235747
"Bled";14.1098719026;46.3668833174
"Bled";14.1108030299;46.367970208
"Bled";14.1111322928;46.3677028565
"Bled";14.1084018746;46.3661700943
"Bled";14.1104603325;46.3674637078
"Bled";14.1107967499;46.3675562949
"Bled";14.1106021124;46.367536787
"Bled";14.1240588945;46.3672267999
"Bled";14.1222190432;46.3668708031
"Bled";14.1243316514;46.3672378861
"Bled";14.1325091805;46.3654378285
"Bled";14.0996935789;46.3598758958
"Bled";14.0994874575;46.359766308
"Bled";14.0996712863;46.3596507937
"Bled";14.099985048;46.359536302
"Bled";14.0995161047;46.3596045864
"Bled";14.0996613962;46.3594617775
"Bled";14.1000804326;46.3592671408
"Bled";14.0997414248;46.3593364487
"Bled";14.1002122854;46.3591512166
"Bled";14.0998338554;46.3592472058
"Bled";14.1002018027;46.358998184
"Bled";14.0998873059;46.3591576559
"Bled";14.1002561384;46.3588546586
"Bled";14.1003893186;46.358657771
"Bled";14.1000201928;46.3589787606
"Bled";14.1008705009;46.3578428228
"Bled";14.1002069715;46.3586833275
"Bled";14.1009955615;46.3581407093
"Bled";14.1002889173;46.3584410515
"Bled";14.1012496568;46.3577018506
"Bled";14.1001725702;46.3584041477
"Bled";14.1013174238;46.357531439
"Bled";14.100342514;46.3583425055
"Bled";14.1015453977;46.3578931131
"Bled";14.1005282553;46.3581100431
"Bled";14.101986546;46.357140825
"Bled";14.1005836225;46.3579035461
"Bled";14.1027805793;46.3570570877
"Bled";14.1010730669;46.357376568
"Bled";14.1015439061;46.3571913302
"Bled";14.1125389369;46.3578889959
"Bled";14.111549411;46.3572065316
"Bled";14.1116737995;46.3575493865
"Bled";14.111814681;46.3576764399
"Bled";14.1119551259;46.3578304808
"Bled";14.1121348421;46.3579668324
"Bled";14.1115717515;46.3574316318
"Bled";14.1124494425;46.3577983306
"Bled";14.1115517439;46.3570625967
"Bled";14.1123346908;46.3576624838
"Bled";14.111566778;46.3569367545
"Bled";14.1121930796;46.3575804108
"Bled";14.111581812;46.3568109124
"Bled";14.1120250458;46.3575251236
"Bled";14.1116362615;46.3566583853
"Bled";14.1119764261;46.3573178135
"Bled";14.1116641422;46.3565416401
"Bled";14.1118880996;46.3571551803
"Bled";14.1117966929;46.3563807226
"Bled";14.1118261964;46.3569657611
"Bled";14.1118822487;46.3567142786
"Bled";14.1111936953;46.3615133602
"Bled";14.1113205707;46.3617032846
"Bled";14.1117203202;46.361895329
"Bled";14.1121082673;46.362816042
"Bled";14.111939031;46.3620319837
"Bled";14.1123719391;46.3625841656
"Bled";14.1120143713;46.3621945158
"Bled";14.1125950243;46.3624509413
"Bled";14.1119682467;46.3626350135
"Bled";14.1128909762;46.3626331789
"Bled";14.1121548282;46.3623485565
"Bled";14.113166619;46.3624643729
"Bled";14.1122739605;46.3622145256
"Bled";14.106708608;46.3719779689
"Bled";14.1063572668;46.3720022148
"Bled";14.1060827291;46.3720990364
"Bled";14.1058340364;46.3722050564
"Bled";14.1064306964;46.372281697
"Bled";14.1054032461;46.3723186485
"Bled";14.1055467941;46.3722837833
"Bled";14.1062085834;46.3723519374
"Bled";14.1053316533;46.3727229553
"Bled";14.1049717192;46.3724772184
"Bled";14.1057380692;46.3725102054
"Bled";14.0900706866;46.3626158037
"Bled";14.0900015352;46.3620844268
"Bled";14.0900185621;46.3618416417
"Bled";14.1130867268;46.364991926
"Bled";14.1127733976;46.3650794658
"Bled";14.1122673322;46.3650305527
"Bled";14.1130816309;46.3653067833
"Bled";14.1127824598;46.3653224565
"Bled";14.1124180233;46.3653556165
"Bled";14.1125057815;46.3655542328
"Bled";14.1128708018;46.3654850889
"Bled";14.112476295;46.3657699332
"Bled";14.1120725791;46.3658207813
"Bled";14.1131765629;46.3658653369
"Bled";14.1126161795;46.365959957
"Bled";14.1123402258;46.3661467532
"Bled";14.1123250449;46.3662815911
"Bled";14.1122711703;46.3663981346
"Bled";14.1013565062;46.3551475229
"Bled";14.1012107882;46.355317322
"Bled";14.1016259542;46.3553565729
"Bled";14.101352082;46.3554174003
"Bled";14.10193615;46.3554579774
"Bled";14.0999977724;46.3555956869
"Bled";14.1022069278;46.3555860628
"Bled";14.1015669076;46.3557879683
"Bled";14.1016674567;46.3559956909
"Bled";14.1027753555;46.3557884601
"Bled";14.1024393186;46.3556778579
"Bled";14.1107932315;46.3637685082
"Bled";14.1095005159;46.3633445834
"Bled";14.1106189017;46.3632993054
"Bled";14.1099723929;46.3638970778
"Bled";14.1096968792;46.3640568799
"Bled";14.1086771934;46.3636260743
"Bled";14.1088840792;46.3636906662
"Bled";14.109170248;46.3636749019
"Bled";14.1093504148;46.3637842701
"Bled";14.1090391119;46.3645465946
"Bled";14.1090579567;46.3641868592
"Bled";14.1091509655;46.3640616251
"Bled";14.1089310835;46.3639969324
"Bled";14.1085900086;46.3641922092
"Bled";14.1085095538;46.3643445319
"Bled";14.1084488254;46.3640831438
"Bled";14.1083550831;46.3642533569
"Bled";14.1081431071;46.3637028834
"Bled";14.1073815674;46.363382044
"Bled";14.1061239734;46.3624005376
"Bled";14.102988873;46.3625919157
"Bled";14.1026743635;46.362751395
"Bled";14.0992319425;46.3563364132
"Bled";14.0980329231;46.356551888
"Bled";14.0986564223;46.3565658017
"Bled";14.0990459061;46.3565868654
"Bled";14.0989297116;46.3565409644
"Bled";14.0992406481;46.3565973967
"Bled";14.1001355174;46.3567034105
"Bled";14.0996953913;46.3566009782
"Bled";14.1008809778;46.3572041135
"Bled";14.1000779345;46.3570448459
"Bled";14.0991275405;46.3571543239
"Bled";14.0990535759;46.3569108203
"Bled";14.0998769862;46.3574121439
"Bled";14.0998536596;46.3572500131
"Bled";14.1000729129;46.3573507066
"Bled";14.1002666243;46.3574242076
"Bled";14.1004997577;46.3574710272
"Bled";14.1006265867;46.3576609632
"Bled";14.100275778;46.3576582034
"Bled";14.1003745537;46.3579738779
"Bled";14.1210228506;46.3612294581
"Bled";14.1198731969;46.3599880176
"Bled";14.1200907654;46.3601966244
"Bled";14.1212529894;46.3614651505
"Bled";14.1208341606;46.3624606044
"Bled";14.1199798642;46.3630568355
"Bled";14.1197567943;46.3631900744
"Bled";14.1178329828;46.3648307065
"Bled";14.1207693393;46.363260844
"Bled";14.1172502036;46.3655099849
"Bled";14.1176010643;46.365512693
"Bled";14.1193500519;46.3642395979
"Bled";14.119219239;46.3642925727
"Bled";14.1168973134;46.3656332188
"Bled";14.1172195765;46.3657976541
"Bled";14.1169323839;46.36587641
"Bled";14.117891981;46.3660097755
"Bled";14.117926332;46.3662979462
"Bled";14.1165937908;46.3659187799
"Bled";14.11682219;46.3662624322
"Bled";14.117488268;46.3660606427
"Bled";14.1163134986;46.3663754637
"Bled";14.116453688;46.366547491
"Bled";14.116321416;46.3666904217
"Bled";14.1159844139;46.3666338345
"Bled";14.1172628612;46.3663378114
"Bled";14.1162017032;46.3668604405
"Bled";14.1170377419;46.3665969878
"Bled";14.1174671596;46.3665643147
"Bled";14.1155181141;46.3673409955
"Bled";14.1152521082;46.3677168137
"Bled";14.1165077852;46.3672226878
"Bled";14.1150037436;46.3678048622
"Bled";14.1157841919;46.3677659147
"Bled";14.1153506972;46.3680504673
"Bled";14.1162635697;46.3678595912
"Bled";14.1162155057;46.3676162993
"Bled";14.116245704;46.3673556183
"Bled";14.0933335122;46.35470631
"Bled";14.0931774571;46.3547140696
"Bled";14.0912898052;46.352575774
"Bled";14.0944740863;46.3540945504
"Bled";14.0926108257;46.3536209285
"Bled";14.0902161278;46.3530710724
"Bled";14.0907093683;46.3531019871
"Bled";14.0936163137;46.3541057483
"Bled";14.0924363065;46.3547441776
"Bled";14.0933729308;46.3570368638
"Bled";14.0940665756;46.3543792288
"Bled";14.0937292267;46.3543495642
"Bled";14.0935669294;46.3570923842
"Bled";14.0937316598;46.3549883756
"Bled";14.0937344967;46.3571746861
"Bled";14.0940203719;46.3556024644
"Bled";14.0945376714;46.3573250022
"Bled";14.0938241077;46.3572563699
"Bled";14.093650687;46.3567421625
"Bled";14.0938557443;46.356914732
"Bled";14.0945424266;46.3570371337
"Bled";14.0940085345;46.3571048812
"Bled";14.0943182799;46.357233294
"Bled";14.094495275;46.357531599
"Bled";14.0941593931;46.3574119767
"Bled";14.0946625478;46.3576318913
"Bled";14.0942091346;46.3575473268
"Bled";14.0943111453;46.3576650967
"Bled";14.0954377388;46.3571161965
"Bled";14.0954522161;46.3570263403
"Bled";14.095592613;46.3571804011
"Bled";14.0946560101;46.3580277105
"Bled";14.0955779875;46.3572792531
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"Bled";14.0844089734;46.3701281349
"Bled";14.0850864117;46.3715910791
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Martin Davis | 3 Dec 18:09 2008
Picon

Re: Get concave hull from an array of longitude in latitude points

I think the ideas for the solution have already been posted on this 
thread - you either need to use alpha shapes or one of the concave hull 
algorithms.  It sounded like pgrouting has an alpha shapes 
implementation - that would probably be the easiest way forward.  
Implementing the other algorithms would be non-trivial.

It might also help if you posted a picture of what you think the desired 
output should be, for the sample data you posted.

Aleš Kecman wrote:
> Hi!
>
> I'm still struggling with this "concave hulls" and it seems I just 
> can't find the way how to do it. I'm sending a text file with some 
> longitude and latitude points of selected subarea from which I need to 
> get a concave polygon. There is only one polygon in attached text 
> file. In my database I have around 500 000 points from which I need to 
> form around 700 polygons. If there is a way to do it in PostGis I 
> would really appreciate any help. I also attached a jpg picture of my 
> convexhull polygon. Thanks!!!
>
> Greets, Ales.
>
>
>
> On Mon, Nov 24, 2008 at 12:13 PM, Mark Cave-Ayland 
> <mark.cave-ayland <at> siriusit.co.uk 
> <mailto:mark.cave-ayland <at> siriusit.co.uk>> wrote:
>
>     Aleš Kecman wrote:
>
>         Hi!
>
>
>         I'm new to Postgis and would really like to get some help on
>         getting a concave hull from an array of points.
>
>         For example:
>
>         I have an array of points - longitude and latitude of
>         buildings in particular area in the city. I already managed to
>         get a convex hull polygon from this array of points, but this
>         is not really helpful. What I'm trying to get is some kind of
>         concave hull polygon from an array of points, which I would
>         further like to use in Google Earth kml file.
>
>         Thanks.
>
>
>
>     Hi Aleš,
>
>     Does ST_Union() help you at all?
>
>
>     ATB,
>
>     Mark.
>
>     -- 
>     Mark Cave-Ayland
>     Sirius Corporation - The Open Source Experts
>     http://www.siriusit.co.uk
>     T: +44 870 608 0063
>     _______________________________________________
>     postgis-users mailing list
>     postgis-users <at> postgis.refractions.net
>     <mailto:postgis-users <at> postgis.refractions.net>
>     http://postgis.refractions.net/mailman/listinfo/postgis-users
>
>
> ------------------------------------------------------------------------
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> postgis-users mailing list
> postgis-users <at> postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users

--

-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022
Martin Davis | 3 Dec 18:46 2008
Picon

Re: Get concave hull from an array of longitude in latitude points

You might also check out this paper:

http://www.foss4g.org/index.php/foss4g/2008/paper/view/226/157

It uses a "connect-buffer-simplify" approach. 

Martin Davis wrote:
> I think the ideas for the solution have already been posted on this 
> thread - you either need to use alpha shapes or one of the concave 
> hull algorithms.  It sounded like pgrouting has an alpha shapes 
> implementation - that would probably be the easiest way forward.  
> Implementing the other algorithms would be non-trivial.
>
> It might also help if you posted a picture of what you think the 
> desired output should be, for the sample data you posted.
>
> Aleš Kecman wrote:
>> Hi!
>>
>> I'm still struggling with this "concave hulls" and it seems I just 
>> can't find the way how to do it. I'm sending a text file with some 
>> longitude and latitude points of selected subarea from which I need 
>> to get a concave polygon. There is only one polygon in attached text 
>> file. In my database I have around 500 000 points from which I need 
>> to form around 700 polygons. If there is a way to do it in PostGis I 
>> would really appreciate any help. I also attached a jpg picture of my 
>> convexhull polygon. Thanks!!!
>>
>> Greets, Ales.
>>
>>
>>
>> On Mon, Nov 24, 2008 at 12:13 PM, Mark Cave-Ayland 
>> <mark.cave-ayland <at> siriusit.co.uk 
>> <mailto:mark.cave-ayland <at> siriusit.co.uk>> wrote:
>>
>>     Aleš Kecman wrote:
>>
>>         Hi!
>>
>>
>>         I'm new to Postgis and would really like to get some help on
>>         getting a concave hull from an array of points.
>>
>>         For example:
>>
>>         I have an array of points - longitude and latitude of
>>         buildings in particular area in the city. I already managed to
>>         get a convex hull polygon from this array of points, but this
>>         is not really helpful. What I'm trying to get is some kind of
>>         concave hull polygon from an array of points, which I would
>>         further like to use in Google Earth kml file.
>>
>>         Thanks.
>>
>>
>>
>>     Hi Aleš,
>>
>>     Does ST_Union() help you at all?
>>
>>
>>     ATB,
>>
>>     Mark.
>>
>>     --     Mark Cave-Ayland
>>     Sirius Corporation - The Open Source Experts
>>     http://www.siriusit.co.uk
>>     T: +44 870 608 0063
>>     _______________________________________________
>>     postgis-users mailing list
>>     postgis-users <at> postgis.refractions.net
>>     <mailto:postgis-users <at> postgis.refractions.net>
>>     http://postgis.refractions.net/mailman/listinfo/postgis-users
>>
>>
>> ------------------------------------------------------------------------
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> postgis-users mailing list
>> postgis-users <at> postgis.refractions.net
>> http://postgis.refractions.net/mailman/listinfo/postgis-users
>

--

-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022

Gmane