Lab 8 Flashcards
GEOCODING OVERVIEW
Process of creating geometric representations for locations (such as points) from geocodes (such as street addresses or ZIP Codes), Uses a computer program called a geocoding engine that employs code tables and rules to standardize address components and carry out “fuzzy matching”
Geocoding examples
Survey of visitors to an arts event
Hospital
Store Chain locations
POLYGON GEOCODING
Assign each record to a polygon, Spatially join to count the records for each polygon, Symbolize using a choropleth map or graduated point symbols
US Census TIGER files
Digitized from 1:100,000 scale maps
Pros:
* Free and easy to download
* Uniform across jurisdictional lines (nationally)
* Street address formatting works well with standard GIS geocoding capacities
Cons:* Incomplete data
* Placement of address point is approximate
MAF/TIGER
produces mail-out census forms & ACS random samples
ZCTAs (tabulation areas)
Approximations for census purposes
* Do not reflect actual ZIP Code areas and are not kept up to date
Parcel address points (local jurisdictions)
Pros:
* Accurate placement of residential location (parcel positional data is often very good, e.g., +/- 5 meters or less)
Cons:
* May need to contact individuals within agencies to get most up todate data
* May not be available, or may cost a substantial amount of money
* Data ends at jurisdictional boundaries
* Data files tend to be very large
Street center lines (local jurisdictions)
Pros:
* Potential to be more up to date (often yearly updates,sometimes quarterly)
* Often adequate accuracy to meet city infrastructure needs(typically +/- 10 meters or less)
Cons:
* May need to contact individuals within agencies to get most up-to-date data
* Data ends at jurisdictional boundaries
Online geocoding
Pros:
*Fast and easy to access
*Free or inexpensive
Cons:
*Loss of privacy/confidentiality
*Requires Internet connection
*Accuracy?
