GeoCoding and Addressmatching in GIS

1
UST/ENV/PAD/PDD 642/742 Introduction to
Geographic Information Systems
Lecture 8 Geocoding
2
Geocoding Defined

• The process by which spatial locations are
  determined using coordinate locations specified
  in a database table
• Results can be events points or routes
  lines

3
Address Geocoding Defined

• The process by which spatial locations are
  determined using addresses specified in a
  database table
• Addresses in the database table are matched to
  address ranges specified in a reference spatial
  data set streets or ZIP codes
• Real world coordinates are assigned to every
  matched address, with the real world coordinates
  being derived from the reference spatial data
  set
• Address-matching is an interpolative process
  and therefore not very precise

4
Address Geocoding Applications

• A company can match customer addresses against
  a street network of their distributor service
  areas in order to know which distributor will
  handle a customer. The information could also be
  used to perform marketing analysis for each
  service area
• A police department could use address
  geocoding to analyze crimes by address. These
  locations can be mapped and analyzed with other
  demographic data
• Emergency dispatch operators could use
  geocoding to enter an address, determine who
  should respond, and route emergency vehicles
  and personnel to the address
• A school district could use geocoding to match
  student addresses against a street map of a
  city. Once the homes of students are located,
  school assignments and busing plans can be
  created and analyzed
• Environmental engineers can identify potential
  impacts of storage facilities for hazardous
  materials in populated areas by matching the
  site addresses to a theme containing census data

5
Address Geocoding Process

• Base Data
• A table with addresses
• A reference theme e.g. street segments with
  address ranges
• Process
• Each address is parsed into components and
  the components are compared with the
  address ranges in the reference theme
• When a table address matches the address range
  of a street segment, an interpolation is
  performed to locate and assign real-world
  coordinates to the address
• Interpolation
• The coordinate location of the address is
  estimated using the address ranges of the
  street segment
• The table address of 350 will be located at
  the mid-point of a street segment with even
  address ranges beginning at 302 and ending at 400

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Address Geocoding Example Address Style
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Address Geocoding Implemented Address Locators

• The first step involves setting up Address
  Locators
• Address Locators are stored in the Catalog tree
  of
• ArcCatalog
• Address Locators contains the following
• - path and file name of the reference dataset
• rules for standardized descriptions of numbers,
  
• names, directions, text, etc. in the reference
  dataset
• - parameters for reading address data
• - parameters for matching address data
• - parameters for creating output datasets

8
Address Geocoding Implemented Address Matching
Process

• standardize the address by parsing into
  component parts based on the specified address
  style
• search the reference dataset attributes for
  components that are the same or similar to the
  standardized address
• adjust the spelling sensitivity to determine
  how closely component matches occur
• adjust the minimum candidate and minimum match
  scores for determining rigor in the matching
  process
• perform the matching in batch mode
• evaluate results and interactively match
  individual records

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Address Geocoding Implemented Address Matching
Options

• Spelling Sensitivity
• how much variation to allow in the matching
  process
• low levels would allow Main, Mane and
  Maine as potential candidates for 244 Main
  St
• Score
• score from 0 to 100 for each potential
  candidate based on matching all address
  components based on the chosen geocoding style
• Minimum Candidate Score
• threshold score from 0 to 100 that allows
  reporting of potential candidates
• Minimum Match Score
• rigor specification determining how well
  address in the table match reference layer
  components a score of 75 to 100 is a good match

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Address Geocoding Implemented Output Options

• Side Offset
• offsets a matched address so many map units to
  the left or right of the street segment, based
  on the parity of the match
• End Offset
• applies a squeeze factor at ends of line
  segment to prevent points from being confused
  with matches in other street segments
• X,Y Coordinates
• adds X and Y coordinates in output layer fields
• Standardized Address
• adds the standardized address in an output
  layer field
• Reference Data ID
• adds the value of the ID of the reference
  dataset segment in an output layer field -1 if
  unmatched
• Percent Along
• output layer field containing percent distance
  along reference dataset feature from the from
  node