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How it Works
OpenStreetMap was originally conceived as an opensource solution to the proprietary nature of mapping data in the UK. It combines elements of Google Maps and Wikipedia together to create a crowd source driven map of the world, allowing users to simultaneously develop respective geographies independently. Using Openstreetmap (OSM) as a basis to build the new campus map permitted a team of CU students to design the layout, including features relevant to campus facilities such as parking, through a combination of pre-configured data, satellite image tracing, and first hand accounts. This data, once in place, must transition through numerous forms between OSM and CU before it can be processed and presented in a form that is is usable as a map.
Initially, changes made by editors are saved in databases hosted by OSM. The Overpass API provides an interface for users to copy a subset of the OSM. CU uses this service to receive a snapshot of Boulder in the .osm extension and imports it into a local postgres database utilizing osm2pgsql. Using postgres allows the installation of the add-on postGIS, which provides geospacial data processing support, and may act as an incentive for using postgres over the static/SQLite alternatives supported by the importer.
Tilemill is an editor which styles OSM data by interfacing with the postGIS Database and allowing the individual layers, such as buildings or footpaths, to be selected for modification. These can be further broken down into additional sublayers and edited with the CSS-like language of CartoCSS. This provides much of the same functionality of CSS, but brings additional conveniences through the inclusion of unique built-in functions.