lessons learned from experiments with postgis eleanor tutt [email protected] st. louis
TRANSCRIPT
What is PostGIS?
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
• Free and Open Source• Adds support for geographic objects to
PostgreSQL database (which is also open source)
Why Experiment ??
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
• Growing quantity of data• Increasingly complex analysis needs• Tired of seeing this in ESRI help files:
Continued Concerns
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
• Other priorities besides shuffling data• Fear of reliance on a lesser-known
platformSkills Identified on LinkedIn Profiles
3,000
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The experiment so far…
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
Frustrating - Projections
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
• Need SRID to properly import data (and if you forget, you don’t get a warning)
Frustrating - Projections
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
• SRID has to be in “spatial_ref_sys” table (and not all codes are there by default)
Where’s my SRID???
Frustrating – Projections
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
• No “on the fly” projection – must be constantly aware of SRID and use ST_Transform any time SRIDs don’t match
Exciting – Increased Speed
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
• ArcGIS takes up to 45 seconds to get past the splash screen (let alone adding data)…
• …when half the time, my queries are simple and don’t require a “pretty map” (“Which bus routes are within a half mile of a site?”)
Exciting – New Analysis Capabilities
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
• Drive time polygons/routings
• Converting polygons to lines/splitting lines into line segments
• So much more…
Exciting – ESRI + PostGIS!
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
ArcMap Query Layers + PostGIS
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
Side Benefits – Better Understanding of ArcGIS
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
• Learning a different language helps you think in different ways
• What is intuitive in one system may be possible, but easy to miss, in the other
Side Benefits – Opportunity for “Data Audit”
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
“Export_Output_2.shp”“test_data.shp”“RHCDA20110418.shp”
Conclusions???
Eleanor Tutt | Lessons Learned from Experiments with PostGISProvidence NNIP Meeting | September 2012
• Dealing with projections is incredibly frustrating – especially with data from two states
• Learning curve is steep, but climb-able
• We aren’t ready to leave ArcGIS, yet