Lecture Notes for Clarke, K. C. Analytical and Computer Cartography

Lecture 4: Geocoding

"GEOCODING is the conversion of spatial information into computer-readable form. As such, geocoding, both the process and the concepts involved, determines the type, scale, accuracy and precision of digital maps." (Clarke, p. 49)

Geocoding and Computer Cartography

• Real World broken into phenomena, landscapes
• Phenomena can be broken down into cartographic entities
• Entities are geocoded to become objects
• Geocoding is often a central mapping agency responsibility
• Especially for the base reference layers
• Can geocode geometry and topology
• Attribute encoding important too

Characteristics of Geographic Data

• Location
• Volume
• Dimension (Point, Line, Area, Volume) also Level of Measurment (Nominal, Ordinal, Interval, Ratio)
• Continuity (Feature vs. Field)

Fundamental Properties of Geographic Objects

• Size
• Distribution
• Pattern
• Contiguity
• Neighborhood
  
  
• Shape
  
  
• Scale
• Orientation
  
• Measurement and Fundamental Properties (Fig. 4.5)

Goals of Geocoding Methods

• Minimize Labor Input
• Detect and Eliminate Errors
  
  
  
• Optimize Storage Efficiency
• Maximize Flexibility

Locational Geocodes

• Geographic Coordinates (Lat Long DDD.MMSS or DDD.DDDD)
  
• The UTM Coordinate System
• 

• UTM Zones and Coordinates
• 

• The Military Grid System

• The State Plane Coordinate System
• Other Systems

Geocoding Methods

• Semi-Automated Digitizing
  

• Automated Digitizing (Scanning)
  

Topological Geocoding

• Evolution of Topology using the Census Bureau's Data as an Example
• Address Coding Guide (1967)
• Led to 1970 use of DIME/GBF system
  
• Extended to all SMSAs in 1980
• For 1990, Replaced with TIGER system

• 
• For 2000 will become TIGER/SDTS

Keith C. Clarke Last Update 4/10/97 Copyright Prentice Hall (1995)