Paul,
I can't find a suitable gnomic srid for PostGIS.
I have tried this:
INSERT INTO spatial_ref_sys (srid, proj4text) VALUES (55000, '+proj=gnom
+lat_0=90 +lon_0=-7.646288');
but I get this when I use ST_Transform.
UPDATE data.osm_county SET geom55000 = ST_Transform(geog4326::geometry,55000);
AddToPROJ4SRSCache: could not parse proj4 string '+proj=gnom +lat_0=90
+lon_0=-7.646288' major axis or radius = 0 or not given
I understand your position about things being hard.
At the moment I would be satisfied with a way of taking OSM data and
successfully (aka no topological errors) projecting it so that I can achieve
what I need to do the projected geometry data.
regards
Simon
On Tue, 22 Jan 2019 03:41:21 +1100, Paul Ramsey <pram...@cleverelephant.ca>
wrote:
If it’s just Ireland, transform to a good Irish projection after casting to geometry.
For maximum awsomeness, transform to gnomonic, in which great >circles are
represented as straight lines… then even all the introduced points will be at the
correct geographic locations. Works for smaller areas, like >Ireland.
P
On Jan 20, 2019, at 9:23 PM, Simon Greener <si...@spatialdbadvisor.com> wrote:
Folks,
I'm in a situation where I need to ST_Union or ST_Collect some osm_county
Polygon (not MultiPolygon) data for Ireland.
Now, because ST_Union or ST_Collect do not support geography, I cast to
geometry before calling.
select min(a.osm_id) as osm_id, a.name,
count(*) as parts, ST_Union(a.geog4326::geometry)::geography as
geog4326 -- or ST_Collect
from data.osm_county as a
group by a.name;
Whence I get this:
ERROR: lwgeom_area_spher(oid) returned area < 0.0
Investigating I get results like this:
select distinct st_isvalidreason(a.geog4326::geometry) from data.osm_county as
a;
"Hole lies outside shell[-10.2589459 53.9746452]"
etc
I guess this is expected because geodetic lines in the source geography are being
treated as straight in the cast'd >>geometry.
If I use ST_Transform to project a 4326 poly to a 3857 and then call the ST_Union
aggregate, or identify a single >>geography that has the invalidity and execute
a self-union, I get the following in both situations.
ERROR: GEOSUnaryUnion: TopologyException: Input geom 0 is invalid: Hole lies outside
shell at or near point >>-1148162.9982628345 7095296.1166736316 at
-1148162.9982628345 7095296.1166736316
I can't for the life of me work out how to complete the aggregated ST_Union on
the 4326 geography data.
Anyone point out what I am doing wrong or give me a pointer to what I can do to
achieve the aggregated union?
Regards
Simon
--------------------------------------------------------------------------------------------------------
Spatial Advice & Solutions Architecture
Database Spatial Stored Procedure Designer
Oracle Spatial, SQL Server, PostGIS, MySQL, ArcSDE FME
Awarded "2011 Oracle Spatial Excellence Award for Education and Research"
A: 39 Cliff View Drive, Allens Rivulet, 7150, Tas, Aust
W: www.spdba.com.au
E: si...@spdba.com.au
V: +61 362 396 397
M: +61 418 396 391
GITC Supplier: T1005
Skype: sggreener
Long: 147.20515 (147° 12' 18" E)
Lat: -43.01530 (43° 00' 55" S)
GeoHash: r22em9r98wg
NAC:W80CK 7SWP3
_______________________________________________
postgis-users mailing list
postgis-users@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/postgis-users
--
Regards
Simon
--------------------------------------------------------------------------------------------------------
Spatial Advice & Solutions Architecture
Database Spatial Stored Procedure Designer
Oracle Spatial, SQL Server, PostGIS, MySQL, ArcSDE FME
Awarded "2011 Oracle Spatial Excellence Award for Education and Research"
A: 39 Cliff View Drive, Allens Rivulet, 7150, Tas, Aust
W: www.spdba.com.au
E: si...@spdba.com.au
V: +61 362 396 397
M: +61 418 396 391
GITC Supplier: T1005
Skype: sggreener
Long: 147.20515 (147° 12' 18" E)
Lat: -43.01530 (43° 00' 55" S)
GeoHash: r22em9r98wg
NAC:W80CK 7SWP3
_______________________________________________
postgis-users mailing list
postgis-users@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/postgis-users
