How to create and use GIS aliases
Issue
In many cases, your GIS map street names will not match the names in your crash record database. If the difference is significant, (i.e. ArcView can’t see them as being similar names) then that location will not be geocodable. This is common when a state highway runs through a city. The city may use a local street name when entering crash data, and the map may use the highway name.
Explanation
In order for ArcView to be able to identify a location, it must be able to make a pretty good match on the primary and cross street names. For example: Central Av will suffice for Central Avenue or sometimes even Centrl Av (depending on if there are closer matches). Also Map Magic does some checking of its own to see how good other matches are.
But, if a name is far different between the crash data and the map data, you must use a GIS Alias in Map Magic to tell ArcView what it should be geocoding. For example: Your crash data may use “HWY 01”, while your map uses “BROADWAY”. This requires a GIS Alias.
Solution
GIS Aliases are kept in the optional ODBC database file that can be created for Intersection Magic. (in version 6.6 and above, see help / what’s new in this version / data for help on setting up the necessary ODBC share)
Once the ODBC share has been set up, you can begin adding GIS Aliases to it. Follow these steps:
- Create a text file containing the Crash DB names and GIS names. Each line should contain the Crash DB name, followed by a comma, followed by the GIS name. (i.e. “HWY 01″,”BROADWAY”)
- Save that file. Any name will do, use GISAlias.del for now.
- Open Utilities / Database / Streets Manager and click on GIS Aliases / Add list. Specify the file that you just created.
That’s it. Your GIS alias will be stored in the ODBC database and available whenever you geocode locations.
Note: What the GIS alias engine really does is a strict search-and-replace within the location string before it is sent for geocoding. Thus, when the location “HWY 01 & CENTRAL” is about to be sent to ArcView for geocoding, the GISAlias engine replaces HWY 01 with BROADWAY, resulting in “BROADWAY & CENTRAL” being sent to ArcView
What this means is that you can do parts of street names (i.e. “HWY”, “HIGHWAY”) or text that includes the “&” in the name (i.e. “HWY 01 & RAMP TO”, “BROADWAY & “) The latter would convert “HWY 01 & RAMP TO CENTRAL” to “BROADWAY & CENTRAL”.
| åÊåÊ | The one thing that GISAliases can’t do at this time, is handle street names that change on the map, but not on the data. For example, if PARK ST changes it’s name to SUNNY ST after it crosses BROADWAY, but the crash data always uses PARK ST, the GISAlias engine will not try both combinations.
In this case, the only solution we’ve come up with is to set up the alias for PARK ST first; do the geocoding; then set up the alias for SUNNY ST; then geocode again, skipping locations that have already been geocoded. Since IMW stores the x,y locations found during geocoding, you only have to do this process once. |