Presentation on theme: "Geocoding …what is it good for? Alex Rodriguez 605-773-5688."— Presentation transcript:
Geocoding …what is it good for? Alex Rodriguez
Geocoding defined: "Geocoding" is the process of matching records in two databases: your address database (without map position information) and a reference street database/layer (with map position information). Before geocoding: After geocoding:
Why geocode? Location, location, location... Emergency Response/Management Fire Police Medical Retail Sales Taxes: In/Out of city Marketing Where are my customers? Where do I advertise? Real Estate House Statistics/Locations Market/Sales analysis Criminal analysis Crime statistics Crime analysis (what crimes happen where?) Crime prevention (registered sex offenders) Demographic Analysis w/Census Statistics Labor Statistics w/Census Statistics Health/Human Services Where are illnesses occurring? How can geocoding serve your agency?
So how do I geocode? Supplies: ArcView 3.x or ArcView 8.x Road Layer with appropriate attributes with geocode index built A table of addresses to be geocoded …show me. Scissors (rounded tip) glue ruler construction paper …adult supervision
Set up the road layer: Theme > properties > geocoding 1) Select the Address Style 2) assign field names 3) Build the geocode index* * build the geocode index if it isnt already built ArcView 3.x
Get the address table: Tables > Add > pierresample.dbf Address in one field... ArcView 3.x
Set up the geocode environment: View > Geocode Address... The source street layer If there is an external road table The style of address used The table containing the addresses to be geocoded The field in that table containing the address The field in that table containing the zone* * Zone in our case refers to a Zip Code Field to use for labels Distance to offset from the street centerline Street Alias Tables Name The output shapefile location and name Define all the geocoding parameters: Set scoring parameters ArcView 3.x
Set up the geocode environment: Define all the scoring parameters: Launch the geocoder ArcView 3.x
Manage the results: Rematch records: All records Selected records Partial match records No match records Modify parameters: All records Selected records Partial match records No match records Interactive Match: ArcView 3.x
Interactive Match: For each address Interactively choose the best match ArcView 3.x
For all your efforts: A new shapefile ArcView 3.x
For all your efforts: With an attribute table - Match Status - Match Score - Match Side - Lat/Long Coordinates (stored in the Shape field) Add the Lat/Long values: - Set the table to editable - Add fields (x-coord, y-coord) - Calculate each field (x-coord = Shape.GetX) (y-coord = Shape.GetY) - Save the changes ArcView 3.x
What if Im running ArcView 8.x? Its basically the same thing. Just a different interface… …walk this way...
Set up the geocoding environment: In ArcCatalog: Create a new Geocoding Service ArcView 8.x
Set up the geocoding environment: In ArcCatalog: Select the Service type* This is the typical address style for addresses in the US * File vs GDB Geocoding Service: File: Build a geocoding service (index) from a shapefile road layer GDB: Build a geocoding service (index) from a GeoDatabase road layer ArcView 8.x
Set up the geocoding environment: Name the service Pick the road layer Assign the fields Set scoring options Set output options Select output fields ArcView 8.x
Set up the geocoding environment: In ArcCatalog: You now have a new Geocoding Service ArcView 8.x
Use the new Geocoding Service: Tools > Geocoding > Geocode Addresses... ArcView 8.x
Use the new Geocoding Service: Add the new Geocoding Service to your project ArcView 8.x
Use the new Geocoding Service: Add the new Geocoding Service to your project The geocoding service we just created ArcView 8.x
Use the new Geocoding Service: Find the address table to be matched Assign the field names Define output Shapefile/Feature Class Define Geocoding options Define Geometry options ArcView 8.x
Use the new Geocoding Service: Define geometry options: Use what spatial reference for the output shapefile? ArcView 8.x
Use the new Geocoding Service: Define geocoding options: Define alias table Set scoring parameters We dont use intersections Define output options Define output attribute options ArcView 8.x
Manage the results: Rematch records: All records Selected records Partial match records No match records Modify parameters: All records Selected records Partial match records No match records Interactive Match: ArcView 8.x
For each address Interactively choose the best match Manage the results: ArcView 8.x
For all your efforts: A new shapefile ArcView 8.x
For all your efforts: In the output table... ArcView 8.x
Geocoding Pitfalls: There are many things that can cause an address not to be geocoded: Irregular addresses Improperly attributed road layer Incompletely attributed road layer PO Boxes cant be geocoded Lat/Long values are the result of mathematical calculations …please explain Murphys Geocoding Law... Your geocoding results are only as good as your data...
Geocoding Pitfalls: Irregular addresses: One Twenty Three Main St, US Hwy 281 South, P O Box 234, The geocoding machine will have problems normalizing these addresses. The first consideration for the geocoding machine is to normalize the address. The road layer has been identified as having fields that represent: - Left/Right address ranges - Prefix Direction - Prefix Street Type - Street Name - Suffix Type - Suffix Direction - Left/Right Zone (Zip Code) The geocoding machine will have problems identifying which parts of these addresses to assign to each of these address parts. - One Twenty Three - wont qualify as a house number - US Hwy wont qualify as a single street name. As a result the parts get assigned incorrectly - P O Box wont be normalized correctly. There is no house number
Improperly attributed road layer: Geocoding Pitfalls: East Maple St Address to be matched: 135 E Maple Street Maple Street in the real world: Maple Street in the database: Incorrect address range Missing prefix direction
Incompletely attributed road layer: East Maple St Address to be matched: 135 E Maple Street Maple Street in the real world: Maple Street in the database: Geocoding Pitfalls: Missing attribute information
Lat/Long values are the result of mathematical calculations Geocoding Pitfalls: Geocoded address: 150 E Maple St East Maple St. The geocoding machine will find a match and determine that the lat/long values for this address is exactly half way along the line and on the left. Without providing an offset distance for the geocoding machine, that coordinate pair will put the house in the center of the street. Another element for consideration in the calculations is the squeeze distance. The squeeze distance tells the geocoding machine that no address is to appear within a certain distance of the end of the street. This prevents addresses from appearing at the end of the street and on the cross street. squeeze East Maple St offset 100 E Maple St Result: The Lat/Long values are not gospel.
Geocoding Pitfalls: Murphys Geocoding Law: Nobody has the perfect dataset and there are always irregular addresses. If you get 100% matches all the time - someone is lying!
Thanks for coming, drive safely... Questions? Comments?. War Stories? Alex Rodriguez