EAlGIS - Interactive Geospatial Data Analysis

EAlGISGrahame Bowland @angrygoat
 http://ealgis.org/ Can anyone guess! what this map shows?

Public Transport Use! ! (did you spot the train lines?)

EAlGIS • Build a reproducible database of geospatial information • Interactive visualisation and analysis through a web interface • Infrastructure for offline analysis, data- mashups…

Developed for…

Buzzwords! • Backend: Python / Flask / SQLAlchemy / MapServer • Database: PostGIS • Frontend: jQuery, OpenLayers, Bootstrap • Mozilla Personas for user authentication • development: ‘vagrant up’

Reproducibility • Database built up by running ‘recipes’ • Built in loaders for Shapefile, KML, CSV attribute data • Metadata! Database introspection & stored relationship data - attributes to geometries. • Automatically reproject spatial data to map projection (eg. Google Mercator)

Attribute Calculations Simple expression language, attributes looked up against current geometry.
 
 100 * (b7837 + b7840 + b7843 + b7846 + b7864 + b7894 + b7912 + b7921 + b7924) / b7942

Generating this SQL! SELECT sa1_2011_aust.geom_3857, sa1_2011_aust.gid, (100 * (b46_aust_sa1.b7837 + b46_aust_sa1.b7840 + b46_aust_sa1.b7843 + b46_aust_sa1.b7846 + b46_aust_sa1.b7864 + b46_aust_sa1.b7894 + b46_aust_sa1.b7912 + b46_aust_sa1.b7921 + b46_aust_sa1.b7924)) / CAST(b46_aust_sa1.b7942 AS FLOAT) + 0 AS q FROM sa1_2011_aust JOIN b46_aust_sa1 ON b46_aust_sa1.gid = sa1_2011_aust.gid JOIN b01_aust_sa1 ON b01_aust_sa1.gid = sa1_2011_aust.gid WHERE b01_aust_sa1.b3 > 100 AND b46_aust_sa1.b7942 != 0) as subquery using unique gid using srid=3857

How that works • Simple expression language parsed with “pyparsing” • At parse time, look up attributes by name and resolve to SQLAlchemy column objects • Emit into the parse tree • Step back… and it works!

Mash All The Things! • Electoral Analysis • Power Grid utilisation • Mash up data on different geometries

Demo!

Open Source • Licensed under the GPL 3 • github.com/grahame/ealgis/ • github.com/grahame/ealgis-aus-census-2011/

Demo site • http://census.ealgis.org/ • email grahame@angrygoats.net for access (public access coming soon!) • help wanted :-)