[postgis-users] Postgis topology help
I'm after some pointers on how I might use topology in this case: We regularly undertake random stratified two phase trawl surveys for fisheries stock assessments. This requires the survey area to be divided into arbitrary strata, with sample sites randomly defined for each strata. Generally these strata are defined from: 1. depth contours 2. arbitrary lines between contours (generally following a lat or long) 3. areas of land or other excluded areas which are excluded from any strata overlapping them. My current Postgis model defines strata outer boundaries as polygons, holes as polygons, instantiates strata as a set of one or more outer boundaries less any holes. This has the usual issues of slivers overlaps between strata as common boundaries are stored twice, as not always identical. If I used topologies, I could store the constituent lines (contours, etc) and assemble the outer boundaries from these, to give properly normalised polygons. I have seen the docs Strk's presentation, but these to not (to me anyway) list the steps to follow to do something like this, the Postgis functions to carry out those steps. I figure the steps should be: load contour linestrings into a topology table - these will never intersect/overlap by definition load other dividing lines - with extensions to ensure they do NOT need to snap to make nodes, as this can move then off the defining lat/lon, so they always overlap the polygons generate the outer strata boundaries export to geometries - add polygon attribute data based on the constituent linestrings remove any overlapping holes to generate the actual strata Any suggestions as to how to go about this? Thanks, Brent Wood ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
[postgis-users] Postgis geometries to KML
Hi, Does anyone know of a way to generate a KML file directly from postgis geometries? I have open street map road geometries stored in a table which I would like to dump out as a KML to visualise on Google Earth. Would love to hear if someone has already done something like this in the past. Cheers, Ed ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
[postgis-users] PostGIS 2.0.0rc2
The second release candidate of PostGIS 2.0.0 is now available: http://postgis.org/download/postgis-2.0.0rc2.tar.gz We hope you'll test and let us know (http://trac.osgeo.org/postgis) if you find problems! Yours, The PostGIS Team ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
[postgis-users] what about 3d-srids
Hey there i was wondering how 3D referencing systems will be handled in the future in PostGIS? When 3D-Datatypes, -Indexes, -Functions are introduced to the PostGIS-World why are no 3D-srids delivered in the spatial_ref_sys by default? I know that there are insert-stmts out there (spatialreference.org), but it seems to me, as there hasn't been much of a discussion around it yet, nobody knows what to do with it. I myself don't know much about 3d-crs. I could imagine they are more precise etc. The reason I'm asking is because I have recently ported a CityGML-Database with Import/Export-tool from Oracle to PostGIS (in the context of my Master Thesis), and on the oracle-side, the use of 3D-datatypes and 3D-indexes is restricted to 3d-srids. A bit of a pain but it also makes sense to me. So back to my first question: What is the PostGIS-team (or other users) thinking about the implementation and usage of 3D-crs? Cheers Felix -- NEU: FreePhone 3-fach-Flat mit kostenlosem Smartphone! Jetzt informieren: http://mobile.1und1.de/?ac=OM.PW.PW003K20328T7073a ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] raster efficiency
Hi Pierre, Thanks for your answer. To compute profile, here is what I do: Input is a linestring Initializes raster ID to NULL I segmentize to the desired length Force 3D For all points do: Get point in 2d If point does not intersect with current raster ID: get new raster ID Get altitude with ST_Value Set current point with 3rd coordinates ST_3Dlength Here is the full SQL if you want https://github.com/3nids/qWat/blob/0b1ced3781e135d5eb03f5172610fd8889c7ae36/sql/3d.sql I noticed that searching for the correct raster took time, so that's why I keep current raster ID. And having bit tiles, the probability to stay on the same raster is quite high. Also my 14 tiles are 6x9km at 2m, so this is about 3000x4500. Do you suggest to cut them before with gdal and have something like 1000 small tiles rather than my 14 big ones? Thanks Denis On 03/30/2012 03:47 PM, Pierre Racine wrote: I found quite to calculate a profile: it takes approx 1-2 secondes to calculate a profile of 4-6 points. Is there any thing that I can do to fasten the process? How do you compute your profile? What is the best strategy: having more small rasters or a single big one? For raster/vector operations, smaller raster tiles (10x10) is generally preferable/faster. Pierre ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
