Re: Problem importing SHP polygons
Mark Wynter <mark <at> dimensionaledge.com>
2015-03-19 21:17:38 GMT
If Mark's suggestion doesn't fix it...
sounds like the imported geometries in PostGIS are not valid - possibly due to self intersections and on
occasions polygons with zero areas that appear like linestrings - something not uncommon when
converting rasters to vectors.
run some checks on your imported geometries, like
st_isvalid, st_area, geometrytype.
Depending on what you find, you can develop a set of cleaning steps like
where geometrytype in(multi polygon,polygon) etc.
> Message: 5
> Date: Thu, 19 Mar 2015 09:40:07 +0000
> From: Mark Cave-Ayland <mark.cave-ayland <at> ilande.co.uk>
> To: Conrad Bielski <conrad_bielski <at> yahoo.com>, PostGIS Users
> Discussion <postgis-users <at> lists.osgeo.org>
> Subject: Re: [postgis-users] Problem importing SHP polygons
> Message-ID: <550A9977.3000400 <at> ilande.co.uk>
> Content-Type: text/plain; charset=windows-1252
>> On 10/03/15 14:48, Conrad Bielski wrote:
>> I'm having a curious issue importing a polygon SHP file into PostGIS.
>> I'll describe the procedure that I'm using and the problem that I'm
>> having and hopefully somebody has had this issue in the past and fixed it.
>> So the procedure is that I use GRASS to produce a vector from a raster
>> output: (r.to.vect input=MASK output=vecMap feature=area) and then
>> export to SHP file (v.out.ogr -c -e input=vecMap dsn=fname
>> format=ESRI_Shapefile type=area).
>> Now when this SHP file is imported into PostGIS, the type is changed to
>> multistring for some reason. Then when checking the topology, there is a
>> 'ring self-intersection' error. This PostGIS db is then imported into
>> GeoServer, where lines are connecting between different parts of the
>> largest polygon (this should not be happening). If I fix this typology
>> problem, then the largest polygon in the db disappears.
>> The strange thing is the following:
>> 1. Opening the SHP file in QGIS doesn't have this problem
>> 2. Importing the SHP file directly into GeoServer, doesn't generate this
>> problem either.
>> Why is PostGIS having an issue importing this file?
>> Any ideas how to fix this?
>> Thanks in advance for your help,
> Hi Conrad,
> Have you tried disabling the MULTI conversion code in shp2pgsql (add -S
> option to the command line) to see if that helps