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Mar
19
comment building larger polygons from smaller ones *without* a common id in PostGIS
2) I had not seen that post, and it would present a fairly straightforward solution. I guess the question would become how many polygons I could union at a time w/o my system falling over (I may need to do millions spread over a tens of thousands of kilometres). Perhaps way forward would be multi-step: first union/dump within tiles of a much larger-scale grid; then select any polygons that intersect borders of the grid into new table; then union/dump those; then combine all 'freestanding' polygons.
Mar
19
comment building larger polygons from smaller ones *without* a common id in PostGIS
Devdatta -- cheers. 1) Yes, touching polygons should be dissolved so that ultimately no polygons touch.
Mar
19
asked building larger polygons from smaller ones *without* a common id in PostGIS
Jan
22
comment Ordnance Survey TOIDS: converting from strings to integers
I should have been more clear about saving 'space': I was mainly thinking about memory rather than storage. I have run a quick experiment on two tables, one with a single text column populated by 7.5m TOID records and the other with TOIDs converted to bigint. With an index on each, the bigint table was 55% the size of the text table (390Mb vs 707Mb) -- so a significant if not huge difference.
Jan
22
comment Ordnance Survey TOIDS: converting from strings to integers
Sylvester Sneekly -- cheers for that. I am aware that removing the string would require us to take a few extra steps pre-processing any updates, etc. We won't be mixing data with different provenance in this project (I think!), so less need for it, although adding a provenance column would be useful.
Jan
22
accepted Ordnance Survey TOIDS: converting from strings to integers
Jan
22
asked Ordnance Survey TOIDS: converting from strings to integers
Dec
7
answered Why does this simple Python OGR code create an empty polygon?
Nov
15
comment adding multiple points to a linestring in PostGIS
Just confirming that it was unconnected a_lines causing the problem. When I extended them by a short distance (so they visibly crossed the r_lines) and then re-ran the process, the network came up as fully segmentized.
Nov
15
awarded  Scholar
Nov
15
awarded  Supporter
Nov
15
comment adding multiple points to a linestring in PostGIS
Thank you -- that appears to work for the most part. There are a few places where an r_line segment hasn't been broken by an a_line node, but I suspect the a_lines may not actually intersect at those points.
Nov
15
accepted adding multiple points to a linestring in PostGIS
Nov
15
awarded  Student
Nov
15
asked adding multiple points to a linestring in PostGIS