Geocoding Vector or Raster

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GeocodingVector or Raster?
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• Chicago crimes

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Definition

• Geocoding is the process of assigning a location
  to addresses in a table by comparing the
  addresses to those in a reference layer.

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Benefits of geocoding

• Map customer locations
• Planning deliveries
• Giving directions
• Planning future expansion
• Internet mapping
• Driving directions Real estate
• Government applications
• Crime analysis Voter validation

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What do you geocode?

• Tabular data with zip codes, addresses or
  latitude and longitude
• Text
• Databases

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Requirements for geocoding

• ArcCatalog create address locators, geocoding
• ArcMap display geocoded results
• Address locators rules for assigning a location
  to an address
• Reference layer address locator assigns address
  based on information in this layer

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Addresses

• Come in a variety of formats

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Geocoding process
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Reference data

• Needs to cover the same area as data to be
  geocoded
• Needs to have adequate level of detail
• Needs to be current
• Needs to be standardized
• Use standard abbreviations
• Standardize Addresses tool in ArcToolbox

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Address locator

• Specifies the method to interpret a particular
  type of address input, relate it with the
  reference data and deliver a geocoded output.
• The rule base is a collection of files used to
  translate the address data into the desired output

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Building an address locator

• Use ArcCatalog

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Building an address locator
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Alternate names

• A second table used in the geocoding process that
  can contain other names for an address, old
  names, or named landmarks (schools, parks,
  hospitals, etc.)
• Makes use of a join field to tie it back to the
  original reference data records

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Geocoding process
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Address locator styles
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TIGER Files Polygon Topology

• Zip Code
• American Indian Reservation
• Alaska Nature Village Statistical Area
• Tribal Designated Statistical Area
• Tribal Jurisdiction Statistical Area
• Alaska Nature Regional Corp.
• FIPS State Code
• FIPS County Code
• MCD
• Place
• Census Tract/Block Numbering Area
• Tabulation Block

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US Streets
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US One Range
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Output options

• Side offset
• End offset

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Geocoding

• Can do single addresses with the Find tool
• Can do a table of addresses with Geocode
  addresses under the tools menu

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Post-geocoding

• Review or rematch results
• Place uncoded addresses

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Common errors

• Giving a street the wrong directional identifier,
  such as using east instead of west or north
  instead of south.
• Giving a street the wrong suffix or street type
  (e.g., avenue instead of boulevard)
  providing no suffix when there should be one.
• Using an abbreviation the streets database may
  not recognize (e.g., St., Ave., Av., or Blvd.).

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Common errors

• Misspelling the street name.
• Providing an out-of-range, or impossible,
  address. For example, a street is numbered 100 to
  30000, but an extra zero is added, accidentally
  producing the out-of-range number 300000.
• Omitting the address altogether.

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Errors in the Address Locator

• Missing streets
• PO of RFD addresses
• An Alley that is not considered a street
• Street address ranges 99 is not always there
• Accuracy Improvement Project

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Hit rates and match scores

• Hit rates the percent of addresses successfully
  matched.
• Less than 60 ??? What to do??
• Match codes A code representing the success of
  the match process
• U Unmatched T Tied M Match
• Match score 0 to 100 .. 100 is the best

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Geomasking

• Why Geomasking?
• Confidentiality of a patients identity
• In the database latitude and longitude
• On a map specific point
• Two main purposes of geomasking
• Release of data for subsequent analysis
• Spatial patterns (e.g. obesity trends)
• Maps for public release

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Things we Geocode

• Incidents of crimes
• Calls for service.
• Vehicle recoveries.
• What else might be geocoded?

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• Automated pin mapping (point data).
• Cluster or hot spot analysis
• Point accumulation techniques
• Point density measures raster model

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WEB Sites to Visit

• http//www.usps.gov/ncsc/
• http//www.geocode.com/geocode.htm
• http//www.mapquest.com
• http//www.zipinfo.com
• http//webhelp.esri.com/arcgisdesktop/9.2/index.cf
  m?TopicNameGeocoding_tutorial_index