Geocoding

Geocoding
An Introduction

Prof. David Bernstein
James Madison University

Computer Science Department

bernstdh@jmu.edu

Definitions

Geocoding:
- The process of finding the coordinates of an object on the surface of the Earth (or other celestial body)
Digitizing:
- The process of creating an electronic/digital representation (usually a vector representation) of a geometric shape

References Commonly Used in Geocoding

Geocoding Street Addresses

(Courtesy of xkcd)

Geocoding Street Addresses (cont.)

One Approach:
- Digitize street intersections
- Determine the collection of addresses on each segment
- Interpolate individual addresses
Collections of Addresses:
- Actual low and high address
- Potential low and high address
- List of actual addresses

Geocoding Street Addresses (cont.)

Using Potential Addresses and Directed Segments

Common Problems when Geocoding Street Addresses

Digitizing Problems:
- Intersections with incorrect coordinates
Address Collection Problems:
- Missing collections
- Gaps in ranges
- Confusion about odd and even sides
- Duplicate names
Interpolation Problems:
- Words for numbers (e.g., "One" for "1")
- Spelling mistakes/differences
- "Route number" and name for a single segment
- Multiple names for a single segment
- Abbreviations (e.g., "Port" for "Port Republic", "3rd" for "third")

Geocoding (Land-Line) Telephone Numbers

Direct Approach:
- Digitize telephone poles or conduits or street intersections
- Determine the collection of phone numbers on each segment
- Interpolate individual telephone numbers
Indirect Approach:
- Associate each phone number with a street address
- Geocode the street address

Geocoding (Static) Internet Addresses

One Approach:
- Collect the coordinates for each IP address
Another Approach:
- Collect the coordinates of "large" routers/servers
- Collect the set of "nearby" IP addresses
- Interpolate individual IP addresses