1. OSM data by country

   Thu 13 May 2010

   cfarmer

   For part of a traffic simulation project I am currently working on we need country-wide road network data for Ireland. In the past, getting decent road network data for an area this large was quite a task (not to mention expensive and time consuming), however, with OpenStreetMap we have access to this type of data instantly, and for free! In order to download full country coverage all at once, all I had to do was turn to this extremely useful site, which provides links for daily excerpts of OpenStreetMap data for any country in Europe plus several non-country regions such ...

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2. PostGIS ‘select’ statement as vector layer in QGIS

   Tue 27 April 2010

   cfarmer

   Several colleagues of mine have asked whether it is possible to visualise the results of a SELECT statement on a PostGIS database that returns spatial data in QGIS. In other words, can we map the results of something like:

   SELECT id, st_union(the_geom) FROM spatial_table GROUP BY id;
   

   My usual answer to this in the past has been “not yet…”, but now thanks to Giuseppe Sucameli and Jürgen E. Fischer, the answer is a resounding “yes!”. A recent patch to QGIS trunk now makes custom Postgres queries possible via the postgres data provider.

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3. ‘Watch’ long running processes

   Wed 08 July 2009

   cfarmer

   The other day I was loading a shapefile of approximately 11 million records into a PostGIS database (stay tuned for more on that later) and I wanted to know when shp2pgsql was done. Instead of continually checking the console, I decided to ‘watch’ the process using the *nix command watch. I discovered this handy tool a while ago, and have found that for long running processes, I can use watch to notify me when the process has finished, using the following command:

   watch -ben 1 "ps u -C shp2pgsql"
   

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4. Quick guide to setting up a PostGIS database

   Fri 28 November 2008

   cfarmer

   Recently I decided to seriously start using PostGIS to manage my spatial data. As I have several projects on the go, organizing and managing my data effectively has become extremely important, and PostGIS is by far the most convenient way to do this. There is lots of documentation out there that explains in detail how to set up PostGIS, but by far the best reference I’ve found is from Tim Sutton’s blog, mainly because he uses Ubuntu, and sudo-apt gets everything you need to have PostGIS working in minutes.

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