User:Davetoo/GIS

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Notes about personal GIS project.

Unless otherwise noted, all of these comments pertain to postGIS imports using osmosis

Import/link

Don't know about other clients, especially free GIS clients, but Manifold System GIS client can work with a small window of a GINORMOUS postGIS table as long as there is a spatial (gist) index on the relevant geometry column. Some ramifications:

  • Because we can't create an index on Views, they are not very useful for large geometry datasets.
  • Although Manifold can perform it's own joins (e.g. between 'ways' and 'way_tags') within the client, because non-geometry tables have no spatial index, the client must import/link/cache the entire table.

This leads to the conclusion that we must de-normalize the data a bit into a structure closer to that of the simpler osm2psql tools.

Which attributes/columns do we want in the derived tables?

For the import, we want those columns required for:

  • ...rendering hints for the GIS client,
  • ...info for validation/debugging of OSM/source data

For the eventual export back to OSM, we also want:

  • Attributes we might edit that need to be mapped back into our export.