Open Source GISHow we use free tools to do cool things

Martin CatalaDonald Hayward

Why Open Source?

Why Open Source?

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● "Free Open Source Software" (FOSS)o Free ($0)o Free (-dom)

● Control● Flexibility● Quality (more eyes, more

contributors)● Innovation

Why Open Source?

● "Plays nice" with otherso Open Standards mean you can keep

ESRI but still get benefits from FOSSo SHP, WMS, WFS, KML, GeoJSON, etc.

● Enterprise-grade software and supporto Open Source GIS tools are not just toys

anymore (Boundless)

Why Open Source?

● It's more funo Fewer don'ts and can'tso If you can dream it, you can build ito The cool kids are doing it

Why Open Source?

● Still skeptical? ESRI isn't.o Python (ArcPy)o https://github.com/Esri

Why Open Source?

How we use Open Source

● PostGIS (a spatial database system)

● QGIS (a desktop GIS application)

● OpenStreetMap● GeoServer (c.f.

ArcServer)

Our (abbreviated) Toolbox:● Python (GDAL,

Mapnik, cluster computing)

● OpenTripPlanner (Analyst Engine)

● OpenLayers, Leaflet, D3.js (Web Mapping)

Transit Livability Explorer

Made with:● OpenLayers (web map)● PostGIS (backend, analysis)● QGIS (analysis, data management)● ArcMap (analysis)

Transit Livability Explorer

Analysis● Multi-step, often changing hands

several times (ArcGIS -> PostGIS -> QGIS -> etc.)

● Large-scale operations scripted with ArcPy, PostGIS SQL, or GDAL Python on USF Research Cluster

Transit Livability Explorer

Click to select:● OpenLayers translates the click into

(x,y)● A web API queries an indexed

PostGIS table for features intersecting the clicked coordinates

Transit Livability Explorer

Simplified GeoJSON Features with PostGIS:

SELECT ST_AsGeoJSON( ST_Simplify( geom, 100 ) ) FROM `table`;

Transit Livability Explorer

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● Project constraints: o Dynamic web mapo Must work on all major browsers (even

IE)o Quick update when boundaries changeo No server-side processingo No cloud "add-ins"

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First Attempt: ● GeoJSON on

OpenLayers/Leaflet/GMaps● Several layers with many features

and high-resolution boundaries● Worked fine on my computer● Client's browser crashed

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Then we tried... ● Simplifying geometries

o Better, but old version of IE still choked● Rendering static images

o ArcGIS screwed up the georeferencing export

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Finally... ● Re-discovered Mapnik

o Python-based mapping libraryo Custom-made slippy tileso Accepts Shapefiles as inputo Generates 100,000+ map tiles in a few

minutes.

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● Open Source is cheap● Open Source is practical● Open Source is cool

Summary

Questions?