Extractotron

In one of my SotM 2011 talks, I suggested that OSM should have regular extracts of metropolitan areas for major world cities and their surrounding areas, regardless of state or country. This is a repository for a bit of code to make that real. I’ve decided to use Amazon S3 to host files, and EC2 to do the extracting. extract.sh is a script that performs the actual work with Osmosis and terminates its host machine upon completion.

Adding New Cities

Extractotron is run a few times per month, to http://metro.teczno.com. If you have cities to add, you can add them directly to cities.txt and send me a pull request in Github.

cities.txt is a tab-delimited file, and has eight fields:

• group

  One of "Africa", "Asia", "Europe", "Middle East", "North America", "South America", or Oceania.

• geonameid

  It's nice to have a link back to the Geonames dataset.

• top, left, bottom, right

  Geographic bounding box of the metropolitan area. These should be larger rather than smaller to surrounding countryside wherever possible. For example of coverage area, see Moscow.

• slug

  Short, lowercase version of the name with dashes for spaces that's used for files.

• name

  Full name of the city.

Rolling Your Own

To use Extractotron yourself, use run-instance.py:

python run-instance.py <your AWS access key> <your AWS secret> <your bucket name>

By default, run-instance.py instantiates an m2.4xlarge instance with Alestic's Ubuntu 10.04 Lucid instance-store AMI ami-bffa6fd6. You can change the instance type or AMI, see python run-instance.py --help for details.

Currently, the cities list is very short. Help me expand it by modifying cities.txt and sending a pull request via Github.

Code Documentation

The Makefile generates various derived files from the cities.txt file. These scripts are utilities to do the extracts, generate utility scripts, JPG previews, and an HTML index based on the regions specified in index.html. Note the result of this Makefile is checked in at github so there's no immediate need to run make on a fresh clone of the repo.

• build-osmosis-script.py

  Generate the shell script osmosis.sh which uses Osmosis to extract subsets of OSM based on the bounding boxes in cities.txt

• build-osm2pgsql-script.py

  Generate the shell script osm2pgsql.sh which uses imposm to import generated OSM metro subsets into a PostGIS database.

• build-coastshapes-script.py

  Generate the shell script coastshapes.sh which uses ogr2ogr to generate coastline shapefiles.

• build-index.py

  Generate index.html, the current HTML interface to allow download of various extracted OSM data.

• compose-city-previews.py

  Generate the JPG images in previews, snapshot maps of the various metros being extracted.

The scripts generated above are then used by Extractotron to generate the actual extracts. The code for doing the extracts includes

• run-instance.py

  Utility script to create an EC2 instance to run the extract. See above for details.

• extract.sh

  Template for the shell script to do the extraction. run-instance.py substitutes pathnames for the scripts generated in the Makefile so that EC2 can then run the extraction. See also upload-files.sh and kill-self.sh.