rethinking geocoding in utah
TRANSCRIPT
Rethinking Geocoding
Bert GranbergAGRC
Paradigm shift
• 2000:– Geocoding Addresses was cool...
• “Wow, it found it!”
• 2010:– Accurately Locating Addresses is critical
• “Every address must match!”
Basic GIS Locator & Process• Input: Structured Address(es)• Output: Match Candidates and Scores
• Familiar but soooo dated
• Many shortcomings:
– Input Address Data• Un-standardized input addresses• Incorrect zones (zip codes in particular)
– Imperfect Address Source Data• Imperfect zone information• Prefix direction used inconsistently…USPS standard in conflict
with local address vernacular
Shortcomings (cont.)– Process Too Simple
• Single address source dataset (centerlines)• Single search strategy (indexing) ….composite and custom locators allow
more complex logic• Focus on HN + StreetName addresses, what about route/milepost or non-
addressed locations• User expectation for more flexible, simple input interface (google)???
– Output• QCing of results done rarely• Improvements to data and process not easily shared• Historical addresses are next to impossible to find• Range-based, interpolated point may not even be on the property• Address point may not be at preferred location (centroid, frontage, building,
doorstep, driveway, gate)
– Overall All• Different users get imperfect, inconsistent results
Geocoding at AGRC
• “Local data is better data”• “Open, public domain data makes sense”
– Cost– Control– Currency
Utah Registered Voter Geocoding Rate By County, May 2010
Overall Match Rate, Weighted By Population = 95%
0%
80%
60%
40%
20%
100%
Geocoding at AGRC (cont.)
• Web service based• Address, Zone (2 parameters)
• 3 levels of aliasing (composite address locator)
• 95% match statewide (range from 47-98% by county) VISTA database
• Can use zip or incorporated city for “zone”
GCWeb
Service
Commitments Made:
• 911 Committee Goals– 95% Address Match Rate by June 2011– Statewide Address Points June 2012
• VISTA, Elections Management– GIS Precinct Assignment and Counts
• Broadband Project funded Address Point project– 1-2 year time frame for building sustainable
processes– Collect Once application
In progress• Developing Address Point-based location services
– Parcel to Address Polygon to Address Point 'Starting Point' script– Proposed address point data model
• Street Centerline– Incorporate 'address system' as an attribute for potential zone use– Prefix and suffix direction issues
• Developing advanced input address handling logic
• Developing advanced address location logic– Different classes of addresses get handed to different location service
• Functionality to gather improvement data from batch and web app results and pass along to data stewards
• Magic search box beginning to take shape
• New generation, distributed data sharing portal, planning phases
Address Starting Points from parcels
http://gis.utah.gov/code-visual-basic/vba-experiment-building-address-points-from-parcels
Magic Zoom
Input Address Classes• _HN _AlpName (123 Main)• _HN _Pre _AlpName (123 S Main)• _HN _Pre _ AlpName _ Type + Zone (123 S Main St)• _HN _AlpName _ Type + Zone (123 Main St)• _HN _Pre _NumName _Suf + Zone (123 S 300 E)• _Name _IntSep _Name + Zone (Main St and 600 S)• _Milepost + _Route (123.456 NB I-15)• _GeogName (Delicate Arch)• _GeogName + Zone (Riverwoods Conference Center, Logan)
Where Zone = {Zip, City, AddressSystem}
Advanced Match Logic SketchWith Input Address:
• Is Geographic Place?
• Is Milepost & Route?
• Is Intersection?
• Is Numeric Street Type?
• Has Prefix Direction?– Lookup and use Address System Zone from supplied zip/city– Use Prefix enabled locators
• Has No Prefix Direction, Prefix Not Critical for Streetname Within Zone?
– Lookup and use Address System Zone from supplied zip/city– Use Prefix disabled locators
• Has No Prefix Direction, Prefix Is Critical For StreetName Within Zone?
– Use supplied Zip/City Zone– Use Prefix disabled locators– Guess best match? – Return match note that prefix should be used
Other, future considerations
• Interim study on Address Quality in government databases (every address locatable?)
• Centralized Repository & Services• Quality Assessment feedback loop• Utah Addressing Board???• Non-Public Sector Services
– Commercial ??– Open APIs ??