Hello,
We have tables that contains both multi-polygons and empty geometries (MULTIPOLYGON EMPTY). The table has an index on the geometry column. After some updates with empty polygons the index becomes corrupt and we receive the error "Relate Operation called with a LWGEOMCOLLECTION type. This is unsupported change argument GEOMETRYCOLLECTION EMPTY" when we make a spatial selection (ST_Intersects) with a polygon. ST_IsValid returns true for all geometries. If we delete the index the spatial query works without issues. For the moment our workaround is using permanent a "not st_isEmpty) in the where clause. Thank you, Sorin -----Ursprüngliche Nachricht----- Von: [email protected] [mailto:[email protected]] Im Auftrag von [email protected] Gesendet: Mittwoch, 7. Juli 2010 21:00 An: [email protected] Betreff: postgis-users Digest, Vol 99, Issue 7 Send postgis-users mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit http://postgis.refractions.net/mailman/listinfo/postgis-users or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of postgis-users digest..." Today's Topics: 1. Sol Katz Award 2010 Nomination Call (Paul Ramsey) 2. ESRI union (analysis) in Postgis (Teresa Fazio) 3. Re: ESRI union (analysis) in Postgis (Ralf Suhr) 4. Re: error updating multipoint: violates check constraint enforce_geotype (Biddy) 5. manual binaries install for windows (Paul Hastings) 6. Re: Invalid geometry when using select AsText (Lu?s de Sousa) 7. Re: manual binaries install for windows (Paragon Corporation) 8. Re: error updating multipoint: violates check constraint enforce_geotype (Nicolas Ribot) 9. Re: error updating multipoint: violates check constraint enforce_geotype (Nicolas Ribot) 10. Re: error updating multipoint: violates check constraint enforce_geotype (Lu?s de Sousa) 11. Re: WKT raster installation on mac (Shaun Langley) 12. Projection(s) for global point-and-radius searches (David Jantzen) 13. Re: Projection(s) for global point-and-radius searches (Paul Ramsey) ---------------------------------------------------------------------- Message: 1 Date: Tue, 6 Jul 2010 13:00:15 -0700 From: Paul Ramsey <[email protected]> Subject: [postgis-users] Sol Katz Award 2010 Nomination Call To: PostGIS Users Discussion <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 The Open Source Geospatial Foundation would like to open nominations for the 2010 Sol Katz Award for Geospatial Free and Open Source Software. The Sol Katz Award for Geospatial Free and Open Source Software (GFOSS) will be given to individuals who have demonstrated leadership in the GFOSS community. Recipients of the award will have contributed significantly through their activities to advance open source ideals in the geospatial realm. Sol Katz was an early pioneer of GFOSS and left behind a large body of work in the form of applications, format specifications, and utilities while at the U.S. Bureau of Land Management. This early GFOSS archive provided both source code and applications freely available to the community. Sol was also a frequent contributor to many geospatial list servers, providing much guidance to the geospatial community at large. Sol unfortunately passed away in 1999 from Non-Hodgkin's Lymphoma, but his legacy lives on in the open source world. Those interested in making a donation to the American Cancer Society, as per Sol's family's request, can do so at https://www.cancer.org/involved/donate/donateonlinenow/index. Nominations for the Sol Katz Award should be sent to [email protected] with a description of the reasons for this nomination. Nominations will be accepted until 23:59 UTC on August 20th (http://www.timeanddate.com/worldclock/fixedtime.html?month=8&day=20&year=20 10&hour=23&min=59&sec=59). A recipient will be decided from the nomination list by an OSGeo designated selection committee. The winner of the Sol Katz Award for Geospatial Free and Open Source Software will be announced on September 9th at the FOSS4G 2010 conference (http://2010.foss4g.org/) closing plenary in Barcelona, Spain. The hope is that the award will both acknowledge the work of community members, and pay tribute to one of its founders, for years to come. It should be noted that past awardees and selection committee members are not eligible. Past Awardees: 2009: Daniel Morissette 2008: Paul Ramsey 2007: Steve Lime 2006: Markus Neteler 2005: Frank Warmerdam Selection Committee: Jeff McKenna (chair) Daniel Morissette Frank Warmerdam Markus Neteler Steve Lime Paul Ramsey Sophia Parafina ------------------------------ Message: 2 Date: Wed, 07 Jul 2010 09:31:07 +0200 From: Teresa Fazio <[email protected]> Subject: [postgis-users] ESRI union (analysis) in Postgis To: [email protected] Message-ID: <[email protected]> Content-Type: text/plain; charset="iso-8859-15"; Format="flowed" I would like to perform in PostGIS a processing like that performed by the union(analysis) tool of ArcGIS. See here reference http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Union_(Analysi s) <http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Union_%28Anal ysis%29> It is very difficult to add some words to what it does, so I've attached two layers before and after the union. This tool repeats the new created geometries as many times as the number of the geometries which partecipate to the intersection, populating the attribute table with the relative generating geometry values. So, after its execution, it allows you to perform a sum on a column attribute grouping by geometry. Maybe such an operation could be generated using aotmic PostGIS operators. Thank you very much -------------- next part -------------- A non-text attachment was scrubbed... Name: test.zip Type: application/x-zip-compressed Size: 1985 bytes Desc: not available URL: <http://postgis.refractions.net/pipermail/postgis-users/attachments/20100707 /d2872c8c/attachment-0001.bin> ------------------------------ Message: 3 Date: Wed, 7 Jul 2010 09:57:08 +0200 From: Ralf Suhr <[email protected]> Subject: Re: [postgis-users] ESRI union (analysis) in Postgis To: PostGIS Users Discussion <[email protected]> Message-ID: <[email protected]> Content-Type: Text/Plain; charset="iso-8859-15" Hi Teresa, you can enhance the following construct to fit your needs. CREATE VIEW fakeunion AS -- poly1 only SELECT a, b, NULL AS c, NULL AS d, geom FROM poly1 WHERE gid NOT IN ( SELECT p1.gid FROM poly1 p1 INNER JOIN poly2 p2 ON (ST_Intersects(p1.geom,p2.geom)) ) -- poly2 only UNION SELECT NULL AS a, NULL AS b, c, d, geom FROM poly2 WHERE gid NOT IN ( SELECT p2.gid FROM poly2 p2 INNER JOIN poly1 p1 ON (ST_Intersects(p1.geom,p2.geom)) ) -- poly1 & poly2 UNION SELECT a, b, c, d, ST_Intersection(p1.geom, p2.geom) AS geom FROM poly2 p2 INNER JOIN poly1 p1 ON (ST_Intersects(p1.geom,p2.geom)) -- poly1 - poly2 UNION SELECT a, b, NULL AS c, NULL AS d, ST_Difference(p1.geom, p2.geom) AS geom FROM poly2 p2 INNER JOIN poly1 p1 ON (ST_Intersects(p1.geom,p2.geom)) -- poly2 - poly1 UNION SELECT NULL AS a, NULL AS b, c, d, ST_Difference(p2.geom, p1.geom) AS geom FROM poly2 p2 INNER JOIN poly1 p1 ON (ST_Intersects(p1.geom,p2.geom)) ; SELECT * FROM fakeunion WHERE ST_GeometryType(geom) = 'ST_LineString' Gr Ralf Am Mittwoch 07 Juli 2010, 09:31:07 schrieb Teresa Fazio: > I would like to perform in PostGIS a processing like that performed by > the union(analysis) tool of ArcGIS. > See here reference > http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Union_(A > nalys > is) > <http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Union_% > 28An > alysis%29> > > > It is very difficult to add some words to what it does, so I've > attached two layers before and after the union. > > This tool repeats the new created geometries as many times as the > number of the geometries which partecipate to the intersection, > populating the attribute table with the relative generating geometry values. > So, after its execution, it allows you to perform a sum on a column > attribute grouping by geometry. > > Maybe such an operation could be generated using aotmic PostGIS operators. > > Thank you very much ------------------------------ Message: 4 Date: Wed, 07 Jul 2010 11:37:04 +0200 From: Biddy <[email protected]> Subject: Re: [postgis-users] error updating multipoint: violates check constraint enforce_geotype To: PostGIS Users Discussion <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes"; format="flowed" Hi, Nicolas, thanks for your response. I would hope that my query returns multipoints. At least it always has in the test runs. For some reason when I let it run on our large dataset, it doesn't work. As a test I decided to skip that one troublesome column and load the other points. But I get the same error for a different column now. On a dataset of roughly 960k rows, I got the error 8 times. I load data into several multipoint columns. For example, I have one column that stores long, lat and alt as groups of multipoints with 1k points per multipoint and then another column that stores x,y and z as groups of multipoints with 1k points per multipoint. I have 6 of those multipoint columns. I am not sure if an ST_Multi around the ST_Union would do anything. Does anybody have any ideas???? Any help is greatly appreciated, as I don't understand why this is happening at all!! B. Quoting Nicolas Ribot <[email protected]>: >> Hi everyone, >> >> I have a program that updates a table containing multipoints. >> Now, I have several columns with multipoints, but only one breaks >> with the following error: >> >> org.postgresql.util.PSQLException: ERROR: new row for relation "lidarpoints" >> violates check constraint "enforce_geotype_numtarclassidreflect" >> >> The code and setup for the other multipoint geometries is exactly the >> same, which is why I am surprised that it's not working for this one >> case. I feel I am overlooking something simple. >> >> My update sql is: >> "update lidarpoints set numtarclassidreflect = >> ST_UNION(numtarclassidreflect, >> ST_GeomFromEWKT('SRID=4326;MULTIPOINT(2 0 >> -1436)')) where lidarpts_id = currentRowID;" >> >> Does anybody know anything about this? >> > > Hi, > > What is the geographic type of the ST_UNION returned by your query ? > Can it be null, and no constraint allowing null geometries exists in > the table ? > > Nicolas > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > ------------------------------ Message: 5 Date: Wed, 07 Jul 2010 16:59:54 +0700 From: Paul Hastings <[email protected]> Subject: [postgis-users] manual binaries install for windows To: PostGIS Users Discussion <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=UTF-8; format=flowed i'm stuck at a univ where the network won't allow d/l of EXE files. i can't see any ZIP, etc files for the windows install bits so....is there a step-by-step walk thru for installing postGIS manually? thanks. ------------------------------ Message: 6 Date: Wed, 7 Jul 2010 12:16:45 +0100 From: Lu?s de Sousa <[email protected]> Subject: Re: [postgis-users] Invalid geometry when using select AsText To: PostGIS Users Discussion <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=windows-1252 On Tue, Jul 6, 2010 at 2:45 PM, rdelisabeth <[email protected]> wrote: > "MULTIPOLYGON(((-203203.329774775 921205.762417328,-201414.754122524 > 920564.899066353,?.etc etc etc ??..,-263950.345631436 > 1215368.70793936,-263772.821121782 1216068.78335908,-263784.403196605 > 1216749.98205891,-263958.177279213 1216452.48684392)))" Hi, These are cartographic coordinates, you have to request the correct SRID from whomever supplied you with the data. Good luck, Lu?s ------------------------------ Message: 7 Date: Wed, 7 Jul 2010 08:00:57 -0400 From: "Paragon Corporation" <[email protected]> Subject: Re: [postgis-users] manual binaries install for windows To: "'PostGIS Users Discussion'" <[email protected]> Message-ID: <10bdc415b2574e9a8e53e8efc6a6e...@j> Content-Type: text/plain; charset="us-ascii" Paul, There are zip binaries available http://www.postgis.org/download/windows/ Scroll all the way to the bottom of the page where you see PostGIS Binaries - instructions are there -- Also if you want to try the experimental ones -- which are at this point just bug fixes to the stable branch, use these -- these are always packaged as zip files and there is a readme on how to manually install http://www.postgis.org/download/windows/experimental.php Though can't help you too much with the PostgreSQL part. There is a Windows Portable GIS flash project with PostGIS/PostgreSQL for windows, that would do if you need PostgreSQL without installation also http://www.archaeogeek.com/blog/portable-gis/ It's a bit of a hefty download I think, but doesn't require any installation at all -- just unzip and use (has a bunch of other goodies besides PostGIS too :) Leo and Regina http://www.postgis.us -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Paul Hastings Sent: Wednesday, July 07, 2010 6:00 AM To: PostGIS Users Discussion Subject: [postgis-users] manual binaries install for windows i'm stuck at a univ where the network won't allow d/l of EXE files. i can't see any ZIP, etc files for the windows install bits so....is there a step-by-step walk thru for installing postGIS manually? thanks. _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users ------------------------------ Message: 8 Date: Wed, 7 Jul 2010 14:13:32 +0200 From: Nicolas Ribot <[email protected]> Subject: Re: [postgis-users] error updating multipoint: violates check constraint enforce_geotype To: PostGIS Users Discussion <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 > Hi, > > Nicolas, thanks for your response. > I would hope that my query returns multipoints. At least it always has > in the test runs. For some reason when I let it run on our large > dataset, it doesn't work. > > As a test I decided to skip that one troublesome column and load the > other points. But I get the same error for a different column now. On > a dataset of roughly 960k rows, I got the error 8 times. > I load data into several multipoint columns. For example, I have one > column that stores long, lat and alt as groups of multipoints with 1k > points per multipoint and then another column that stores x,y and z as > groups of multipoints with 1k points per multipoint. I have 6 of those > multipoint columns. > > I am not sure if an ST_Multi around the ST_Union would do anything. > > Does anybody have any ideas???? > > Any help is greatly appreciated, as I don't understand why this is > happening at all!! > Hi, What are the constraints defined for the table ? (\d lidarpoints in psql). One row may return null or a geometryCollection, which is rejected by the constraint. You could test the update query by changing it to a select, to see what are the returned type of the st_union: select distinct st_geometryType(ST_UNION(numtarclassidreflect, ST_GeomFromEWKT('SRID=4326;MULTIPOINT(2 0 -1436)'))) from lidarpoints where lidarpts_id = currentRowID; or maybe add a not null where clause, if it appears some rows are returning null values. Nicolas ------------------------------ Message: 9 Date: Wed, 7 Jul 2010 14:17:03 +0200 From: Nicolas Ribot <[email protected]> Subject: Re: [postgis-users] error updating multipoint: violates check constraint enforce_geotype To: PostGIS Users Discussion <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 > Nicolas, thanks for your response. > I would hope that my query returns multipoints. At least it always has > in the test runs. For some reason when I let it run on our large > dataset, it doesn't work. > > As a test I decided to skip that one troublesome column and load the > other points. But I get the same error for a different column now. On > a dataset of roughly 960k rows, I got the error 8 times. > I load data into several multipoint columns. For example, I have one > column that stores long, lat and alt as groups of multipoints with 1k > points per multipoint and then another column that stores x,y and z as > groups of multipoints with 1k points per multipoint. I have 6 of those > multipoint columns. > > I am not sure if an ST_Multi around the ST_Union would do anything. And yes, it may help to force a ST_MULTI, as st_union will try to return the simplest possible type (if I recall correctly). > > Does anybody have any ideas???? > > Any help is greatly appreciated, as I don't understand why this is > happening at all!! > > B. > ------------------------------ Message: 10 Date: Wed, 7 Jul 2010 14:54:31 +0100 From: Lu?s de Sousa <[email protected]> Subject: Re: [postgis-users] error updating multipoint: violates check constraint enforce_geotype To: PostGIS Users Discussion <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 On Tue, Jul 6, 2010 at 11:00 AM, Biddy <[email protected]> wrote: > org.postgresql.util.PSQLException: ERROR: new row for relation "lidarpoints" > violates check constraint "enforce_geotype_numtarclassidreflect" Hi Biddy, If you haven't changed the constraints created on the table by PostGis this error means exactly that you are inserting a geometry that is not of the type declared for the numtarclassidreflect column. To sort this out you have to guarantee that all data feed into that column is either a multipoint or null. I believe that ST_Multi solves your problem. Lu?s ------------------------------ Message: 11 Date: Wed, 7 Jul 2010 12:08:30 -0400 From: Shaun Langley <[email protected]> Subject: Re: [postgis-users] WKT raster installation on mac To: PostGIS Users Discussion <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=iso-8859-1 I'm still getting stuck with this installation. I specified the libdir, but note that libpq is not in this directory. The path for libpq is "/Library/PostgreSQL/8.4/include" which is distinct from the other code libraries in "/Library/PostgreSQL/8.4/lib" I'm copying the directory contents so you can clearly see what's included in each. configure: error: could not find libpq user-d0c71a:wktraster-0.1.6d langleys$ cd ../include/ user-d0c71a:include langleys$ ls ecpg_config.h pg_config.h pgtypes_numeric.h ecpg_informix.h pg_config_i386.h pgtypes_timestamp.h ecpgerrno.h pg_config_manual.h postgres_ext.h ecpglib.h pg_config_os.h postgresql ecpgtype.h pg_config_ppc.h sql3types.h libpq pgtypes_date.h sqlca.h libpq-events.h pgtypes_error.h libpq-fe.h pgtypes_interval.h user-d0c71a:include langleys$ user-d0c71a:include langleys$ cd ../lib user-d0c71a:lib langleys$ ls libecpg.6.1.dylib libpq.dylib libecpg.6.dylib libproj.0.5.5.dylib libecpg.a libproj.0.dylib libecpg.dylib libproj.dylib libecpg_compat.3.1.dylib libuuid.16.dylib libecpg_compat.3.dylib libuuid.a libecpg_compat.a libuuid.dylib libecpg_compat.dylib libuuid.la libgeos-3.2.0.dylib libxml2.2.7.1.dylib libgeos.dylib libxml2.2.dylib libgeos_c.1.6.0.dylib libxml2.a libgeos_c.1.dylib libxml2.dylib libgeos_c.dylib libxml2.la libpgport.a libxslt.1.1.23.dylib libpgtypes.3.1.dylib libxslt.1.dylib libpgtypes.3.dylib libxslt.a libpgtypes.a libxslt.dylib libpgtypes.dylib libxslt.la libpq.5.2.dylib postgis-1.4.so libpq.5.dylib postgresql libpq.a user-d0c71a:lib langleys$ on the first line, you can clearly see that no matter which path I select for "libdir" the configure script cannot find "libpq". Any ideas? Regards, Shaun On Jul 6, 2010, at 5:51 AM, Jorge Ar?valo wrote: > On Mon, Jul 5, 2010 at 6:15 PM, Shaun Langley <[email protected]> wrote: >> it returns /Library/PostgreSQL/8.4/lib >> >> what's the option syntax to add the lib directory during >> configuration? can I specify something like >> >> --with-libdir='/Library/PostgreSQL/8.4/lib' >> > > The option should be --libdir='/Library/PostgreSQL/8.4/lib'. Give it a > try > > Best regards, > Jorge > > >> Cheers, >> Shaun >> On Jul 5, 2010, at 11:51 AM, Jorge Ar?valo wrote: >> >>> On Mon, Jul 5, 2010 at 5:19 PM, Shaun Langley <[email protected]> wrote: >>>> Yes it still complains it can't find libpq. >>>> >>> >>> I didn't try it on mac, but in Windows, I had to add the lib directory to PATH. >>> >>> What happens if you execute pg_config --libdir? >>> >>>> -------------------------- >>>> Shaun Langley >>>> Graduate Student >>>> 208 Manly Miles >>>> Michigan State University >>>> East Lansing, MI 48824 >>>> (517) 974-9346 >>>> >>>> Sent from my iPad >>>> >>>> >>>> On Jul 5, 2010, at 10:48 AM, Pierre Racine <[email protected]> wrote: >>>> >>>>> So now that you had it manually does it still complain that it can not find libpq? >>>>> >>>>> Some systems need us to explicit some installation paths (like Windows) in the configure command. >>>>> >>>>> Pierre >>>>> >>>>>> -----Original Message----- >>>>>> From: [email protected] >>>>>> [mailto:postgis-users- [email protected]] On Behalf >>>>>> Of Shaun Langley >>>>>> Sent: 2 juillet 2010 19:14 >>>>>> To: postgis-users >>>>>> Subject: [postgis-users] WKT raster installation on mac >>>>>> >>>>>> I'm trying to install WKT Raster on Mac OS X, using the >>>>>> enterprisedb installation of postgres, and postgis through the >>>>>> stackbuilder. I've run into a problem when running the >>>>>> ./configure for WKT Raster as it returns an error saying that it >>>>>> cannot locate libpq. The installation of postgres is found at >>>>>> /Library/Postgres/8.4/ and libpq is located within lib/. I had >>>>>> to manully specify the location of pg_config which I did successfully. Any suggestions on how to proceed? >>>>>> >>>>>> Regards, >>>>>> Shaun >>>>>> -------------------------- >>>>>> Shaun Langley >>>>>> Graduate Student, PhD >>>>>> Department of Geography >>>>>> Michigan State University >>>>>> Home: (517) 974-9346 >>>>>> _______________________________________________ >>>>>> postgis-users mailing list >>>>>> [email protected] >>>>>> http://postgis.refractions.net/mailman/listinfo/postgis-users >>>>> _______________________________________________ >>>>> postgis-users mailing list >>>>> [email protected] >>>>> http://postgis.refractions.net/mailman/listinfo/postgis-users >>>> _______________________________________________ >>>> postgis-users mailing list >>>> [email protected] >>>> http://postgis.refractions.net/mailman/listinfo/postgis-users >>>> >>> >>> >>> >>> -- >>> Jorge Ar?valo >>> DEIMOS Space >>> Internet & Mobilty Division >>> Ronda de Poniente 19. Edificio Fiteni VI, portal 2, 2? >>> 28760 Tres Cantos (Madrid) >>> Tel: +34 91 806 34 50 - ext: 155 >>> [email protected] >>> http://gis4free.wordpress.com >>> _______________________________________________ >>> postgis-users mailing list >>> [email protected] >>> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> -------------------------- >> Shaun Langley >> Graduate Student, PhD >> Department of Geography >> Michigan State University >> Home: (517) 974-9346 >> >> >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> > > > > -- > Jorge Ar?valo > DEIMOS Space > Internet & Mobilty Division > Ronda de Poniente 19. Edificio Fiteni VI, portal 2, 2? > 28760 Tres Cantos (Madrid) > Tel: +34 91 806 34 50 - ext: 155 > [email protected] > http://gis4free.wordpress.com > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users -------------------------- Shaun Langley Graduate Student, PhD Department of Geography Michigan State University Home: (517) 974-9346 ------------------------------ Message: 12 Date: Wed, 7 Jul 2010 11:19:51 -0700 From: David Jantzen <[email protected]> Subject: [postgis-users] Projection(s) for global point-and-radius searches To: PostGIS Users Discussion <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset="us-ascii" Hey All, It's been a couple years but happily I have a reason to work with PostGIS again! I'm rusty, and this is pretty a basic question, so if you just specify the chapter in TFM I'll happily go read it. I need to do simple point-and-radius searches for some properties in Germany. Very soon I'll need to do this same thing across Europe and North America, and some in Asia. My understanding is that the accuracy of such measurements will degrade as I use projections covering larger and larger geographical areas. So, some questions: 1) Is there a single global projection that I could use for all such calculations? How bad would the distortions be and where? 2) Assuming the correct path is to switch projections depending on area of focus, what are some strategies for this kind of dynamic switching in SQL queries? Thanks for your help (and patience), David ------------------------------ Message: 13 Date: Wed, 7 Jul 2010 11:40:43 -0700 From: Paul Ramsey <[email protected]> Subject: Re: [postgis-users] Projection(s) for global point-and-radius searches To: PostGIS Users Discussion <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 David, Consider using the GEOGRAPHY type if your queries are just going to be ST_DWithin style. That will remove all projection issues. P. On Wed, Jul 7, 2010 at 11:19 AM, David Jantzen <[email protected]> wrote: > Hey All, > > It's been a couple years but happily I have a reason to work with PostGIS again! ?I'm rusty, and this is pretty a basic question, so if you just specify the chapter in TFM I'll happily go read it. > > I need to do simple point-and-radius searches for some properties in Germany. ?Very soon I'll need to do this same thing across Europe and North America, and some in Asia. ?My understanding is that the accuracy of such measurements will degrade as I use projections covering larger and larger geographical areas. > > So, some questions: > 1) Is there a single global projection that I could use for all such calculations? ?How bad would the distortions be and where? > 2) Assuming the correct path is to switch projections depending on area of focus, what are some strategies for this kind of dynamic switching in SQL queries? > > Thanks for your help (and patience), > David > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > ------------------------------ _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users End of postgis-users Digest, Vol 99, Issue 7 ******************************************** _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
