#POSTGIS IRC Log - 2008-07-09

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00:35:11 epifanio: hi, i've installed a debian lenny via net-install, in synaptic i can't find postgis, do you know what i need to add in /etc/apt/sources.list to have a postgis package ?
02:47:29 epifanio: hi, i'm tring to load a database intp postgresql, but the dump is created using postgresql-8.2 and postgis-1.2 , while the machine where i need to load it use postgresql-8.3 and postgis-1.3
02:49:14 epifanio: i create the dump using : pg_dump namedb > file_dump ; and i'm tring to load the dump, in the 8.3 machine, using : su postgres ; createdb namedb ; psql namedb < file_dump
02:50:46 epifanio: it give me these error : could not access file "/usr/lib/postgresql/8.2/lib/liblwgeom.so.1.2" beacouse i'm using different postgresql version
02:51:16 epifanio: how can i create a dump from 8.2 and load it in the 8.3 :-/ ?
02:57:45 epifanio: ahh i need to install the 8.2 too on the machine that have the 8.3 version
03:16:38 CIA-6: robe * r2836 /trunk/doc/reference.xml: Numerous small changes. Changed some returns 1 ( TRUE ) to just TRUE. Automatic casting between 0 1 and boolean no longer exists in PostgreSQL. Lets not confuse people by suggesting to them they are the same.
03:27:57 epifanio: looking to install the 8.2 too .. i see that in the repo it use the postgis 1.3 ... so i do not have the liblwgeom.so.1.2 needed to load the dump
03:30:17 epifanio: do you think ... can i make a symbolic link like : mkdir -P /usr/lib/postgresql/8.2/lib/ ... sudo ln -s /usr/lib/postgresql/8.2/lib/liblwgeom.so.1.3 /usr/lib/postgresql/8.2/lib/liblwgeom.so.1.2 ?
03:30:21 epifanio: what do you think about ?
07:59:40 mcalder: hi, I was wondering if PostGIS is available for commercial use
08:06:21 nhv: yes use as you want
08:08:18 mcalder: thank you
09:54:09 scheidt11: How to use contains in postgis? I need to get points( lat,long ) from inside a delimited area. How to do this sql command?
09:57:11 mloskot: scheidt11: have you check the manual?
09:59:59 scheidt11: aloskot: yes i read that, but i new, and a quite confuse, with contains, intersect and union
10:01:06 scheidt11: i just want to perform a sql that, given a area( polygon ) and points, return true or false ( if the point is inside or not )
10:01:08 mloskot: if you are new, you need to read the OGC Simple Feature Specification first, to get an idea of what spatial stuff in DBMS is
10:01:16 mloskot: next, check this chapter from the postgis manual
10:01:16 mloskot: 4.6.2. Examples of Spatial SQL
10:01:28 mloskot: and you will see how to use spatial functions, including st_contains
10:01:43 scheidt11: ok
10:01:50 mloskot: and don't forget about this reference
10:01:50 mloskot: http://www.postgis.org/documentation/manual-1.3/ch06.html
10:01:51 sigq: Title: Chapter 6. PostGIS Reference ( at www.postgis.org )
10:09:05 scheidt11: ok, but in the case of points in a area, the better function to use is ST_Contains?
10:09:58 mloskot: st_contains will do the job well
10:10:26 mloskot: but, I re-suggest to look into OGC Simpl. Feat. Spec. where you will get in-depth explanation of functions, with graphical examples
10:10:41 mloskot: so you can easily understand what function does what job
10:22:31 scheidt11: mloskot: the command within works like contains?
10:23:50 mloskot: scheidt11: "like" but different :- )
10:23:58 mloskot: scheidt11: -> check OGC Simple Feature Specification for details
10:24:10 mloskot: believe me, it will help a lot
10:24:37 scheidt11: alrigth : ) )
10:24:41 mloskot: http://www.opengeospatial.org/standards/sfs
10:24:43 sigq: Title: Simple Feature Access - Part 2: SQL Option | OGC® ( at www.opengeospatial.org )
10:24:44 mloskot: OpenGIS Simple Features Implementation Specification for SQL
10:24:47 mloskot: document
12:37:42 landonf: Afternoon
14:58:40 springmeyer_: I have a shapefile with 5 MULTILINES and one LINESTRING
14:59:08 springmeyer_: ogr2ogr bails on importing the LINESTRING because it fails the 'enforce_geotype_geometry' contraint
14:59:43 springmeyer_: while shp2pgql automatically converts the LINESTRING to a MULTILINESTRING type even though it is not a MULTILINESTRING
15:00:30 sindile: hello to all
15:01:44 springmeyer_: I'm curious if anyone knows how shp2pgql makes that assumption to convert to MULTI* - based on the type of the first record encountered?
15:01:51 springmeyer_: hello sindile
15:05:26 sindile: how do i write a single pgsql statement if i have a single multi-polygon postgis layer i want to use the following functions ST_Boundary, node the polylines ( what function ) and ST_Polygonize
15:09:27 springmeyer_: sindile: so you have a table that includes one record that is a multipolygon?
15:10:01 sindile: springmeyer: yes that is correct
15:28:44 springmeyer_: sindile: for nodeing the polylines look into PointN and NumPoints
15:29:02 springmeyer_: whats you ultimate goal?
15:32:55 sindile: springmeyer: ultimately is to clean my data - currently i have smaller polygons inside a bigger polygon ( the smaller ones are not touching the boundary of the bigger one )
15:34:09 sindile: for example when i calculate area of the bigger one it does not take into account the smaller ones, also when displaying them the smaller ones are flooded by the bigger polygon
15:40:54 mleslie: springmeyer: Anyone feel free to correct me, but I believe shp2pgsql always assumes multi just to be safe.
15:50:51 springmeyer_: mleslie: thanks
16:24:03 springmeyer_: sindile: also see the 4th example here: http://www.bostongis.com/blog/index.php?/archives/33-More-generate_series-tricks.html
16:24:05 sigq: Title: More generate_series tricks - BostonGIS Blog ( at www.bostongis.com )
16:41:00 sindile: springmeyer_: thanks will try the documentation
16:41:26 springmeyer_: np: wish I could help more!
16:50:52 zanberdo: it seems that st_within throws an error if I pass a multipoly geom with overlapping polygons. I see an error in the log file: 2008-07-09 17:48:52 PDT NOTICE: TopologyException: side location conflict ( -122.516,37.526,37.526 ) 2008-07-09 17:48:52 PDT ERROR: GEOS within( ) threw an error!
16:52:41 zanberdo: is there a way to permit such overlaps, some overriding function perhaps, or one that joins the separate geoms into a single contiguous geom, in postgis?
16:53:27 zanberdo: the geom itself is being created via a gui. I'm not sure if there is any way for me to check for the overlapping case before I send the geom to postgis.
18:55:43 springmeyer_: is anyone familiar with ST_Segmentize?
18:56:13 springmeyer_: I am running it on high resolution 1:24k hydrography data.
18:57:08 springmeyer_: and am hoping to convert all linestrings ( of variable length ) into equal interval linestrings ( ~500ft )
18:58:19 springmeyer_: seems like ST_Segmentize just adds more nodes to the linestrings and I can't figure out how to extract the intervals I need
19:50:28 jlivni: springmeyer_: maybe st_line_substring?
19:51:41 springmeyer_: jlivni: thanks - I'm actually working that angle now trying to figure out how to use it...
19:52:01 jlivni: http://rafb.net/p/4plb4P13.html
19:52:02 sigq: Title: Nopaste - No description ( at rafb.net )
19:52:23 springmeyer_: would you recommend....
19:52:25 jlivni: thats something i did to get point locations at even distances along a line ( needed to calculate elevations at even pts )
19:52:28 springmeyer_: oh glory
19:52:46 jlivni: so logic should be the same for you -- basically just get the fractions along the line, and then get the line substring between fractions
19:53:01 springmeyer_: yup, and python to boot.
19:53:16 jlivni: i dont know if you need to first manually force a new point in there ( which my function does ), or if substring does it for you ( maybe it goes to closest node, i dunno )
19:53:26 springmeyer_: I am currently ripping my eyebrows out trying to get generate_series to work right...
19:53:45 springmeyer_: hmm, good point
19:53:52 jlivni: i've gotta run but would be happy to assist more manana
19:53:56 springmeyer_: 'point' he he
19:54:03 springmeyer_: super- thanks so so much
19:54:35 jlivni: you'll note im not using generate series .. not sure why'd you need it using the fraction approach
19:54:55 springmeyer_: to iterate through line segments
19:55:12 springmeyer_: pythons %s
19:59:29 jlivni: good point. note my code is extremely inefficient - calling a new qry for each point. but you get the idea...