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bio website cleverelephant.ca
location Victoria, Canada
age 44
visits member for 4 years, 11 months
seen 3 hours ago

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3h
comment Mapnik PGRaster Plugin creating 8x8 tiles with visible boundaries
I have seen the same effect, but only when doing a reprojection within Mapnik. If the source and destination are the same projection, the effect disappears. Another clue.
8h
comment PostGIS - How to calculate linestring length from WGS84 after transforming from OSGB 36
Paste the WKT of the object itself (ST_AsEWKT(geom)) so others can verify.
1d
comment Polygon area calculation in Ruby (on Rails, rgeo, PostGIS and GEOS) in sqare meters
Ellipsoidal math is required for "exact" results over large areas. Equal area projections just spread the error as evenly as possible over their area of validity. For most uses a planar projection is perfectly sufficient.
Jul
4
revised How to create a sequence for a table which was created by selecting data from another table?
added 4 characters in body
Jul
4
answered How to create a sequence for a table which was created by selecting data from another table?
Jul
3
comment Reprojecting in Postgis
You incorrectly loaded the data initially, so you have geometries that think their SRID is 4326 when actually they seem to be in some kind of UTM projection (judging by the coordinates). You'll have to go back and reload the data first.
Jul
3
answered Polygon area calculation in Ruby (on Rails, rgeo, PostGIS and GEOS) in sqare meters
Jul
1
answered How to obtain WGS84 or Projected Bounds for given EPSG in postgis?
Jun
24
comment Converting NAD 83 to WGS 84 in PostGIS
Note that you'll want the to_wgs84 into in both the proj4text and srtext or things won't work as you want.
Jun
24
answered Rectangle Appears Distorted on Map
Jun
22
comment Poor performance with storing large rasters in PostGIS and visualising in QGIS
Who ever said that PostGIS rasters were faster than anything? Find that person and give them a punch in the face. They can be more convenient (handy SQL access API) and they can be useful for analysis (raster and vector in the same bucket) but faster? Never.
Jun
22
answered Draw line with lon, lat, distance and azimuth
Jun
9
comment Number of Neighbors Around a Point
This kind of thing is n*log(n), so not quite linearly, but not quadratically either. I think @johnbarca's suggestion is best, just toss some more cores at it by running several areas in parallel.
Jun
8
answered Number of Neighbors Around a Point
Jun
5
answered How to cut contour lines at the edge of a data source
Jun
4
answered Reprojection not generating properly the tiles
Jun
4
answered Problem with spatial index PostGis
Jun
4
answered Postgis query on 3D cube does not use index
May
30
revised Determine XY offset in meters between two lat/long points (EPSG:4326), and accurately recreating point locations using XY offset
edited body
May
29
comment Speeding up PostGIS ST_AsGeoJSON
You're jumping ahead in your analysis. The problem is almost certainly using a huge string (the output of ST_AsGeoJSON) as a grouping key, not the performance of ST_AsGeoJSON itself. Look at reworking your query to figure out your values, then join back to the geo table to pick up the geometries after.