Geo-coding

Question 1

Geocoding definition

Answer 1

geolocation, collection of algorithms to go from street address to longitude and latitude
Bringing in address data

Question 2

Location reference methods

Answer 2

*Geographic: geographic descriptions that use a coordinate reference system to provide the unique location of an object
Latitude degrees, longitude minute, latitude second, Zone (UTM), Northing (UTM), Easting (UTM)
*Mailing: information on the basis of which a mail item can be forwarded and delivered without searching
Standardise street, primary address number, pre-directional, street name, suffix
*Physical: information that indicates by relationship or by description the unique location of an object
Reference team, from distance, to distance

Question 3

How to put address in GIS

Answer 3

Bring in excel spreadsheet or CVS file
Create street locator or find existing one for street file
Geocode address → rematch address

Question 4

How geo-coding is done

Answer 4

Need reference fill: collection of street segments with associated address range
Take given address (123 Sesame Street)
Find street segment with address range containing (123)
Interpolate location between endpoints

Question 5

Geocoding Problems

Answer 5

Multiple street names
Typos
PO Boxes, rival route numbers, apt numbers, lot numbers in the street address
These need to be deleted

Question 6

Automated Geocoding

Answer 6

Parse: splits up into section
Search against a database
come up with options to choose from - match score
Typical first pass - 60% match
Second pass (try simple multiple names, typos_ = additional 15%
Third pass (detailed examinations)
More work for less return each time through
Hardly any studies will have 100% geo-coding → look and see what happened to the missing ones

Question 7

Morals of geocoding

Answer 7

Ask whether there were any data that could not be geo-coded → when presenting geo-coded data always tell how many addresses could not be matched

Question 8

Does match rate equal accuracy rate

Answer 8

Match rate does not equal high accuracy rate
The terms mean fundamentally different things
Match rate - whether could find in database
Accuracy is that really where that building is located
Attributes of that locations