Centerline Magic
Tim Sosinski
M.J. Harden Associates, Inc., 1019 Admiral Boulevard
Kansas City, MO 64106
The differences between the two procedures may be observed by comparing the corresponding
high address ranges. The theoretical method accommodates an obviously broader range of
address possibilities. There are also a number of different operational impacts other than merely
storing the data:
Table 3: Match Rate Comparison
| Task |
Actual |
Theoretical |
| Maintenance Costs |
Higher |
Lower |
| Match Rate |
Lower |
Higher |
| Location Estimation |
Higher |
Lower |
Which strategy to use for address range recording depends of course on the needs of the user.
Different agencies will of course have different need requirements. Some users find it beneficial
to store and maintain both types of address ranges within their centerline file.
Recalling the example above, the collection of centerline street name and address range information
has been very much like sending field collectors to the field. They would then “walk” each
street segment recording (or filming) the addresses along the way. Although accurate, this
method can be slow. Data collection errors are costly to correct+ften requiring another trip to
the field. With the proliferation of intelligent and spatially-referenced data sets of all kinds, it is
now possible to take advantage of the digital wealth of knowledge to improve the data collection
and construction of street centerline files.
Automatic Address Range Assignment
It is now possible to automatically assign address ranges. The method described below is
applicable in the following instances:
- The user wishes to record actual address ranges
- A spatially-referenced address point file is available for use as a substitute for field verification
- Centerlines lacking address range information must contain accurate street names that are consistent with the street naming conventions of the source point address data
System Inputs
Suitable input data must be available for the process to work properly. Appropriate source point
address information is usually a parcel centroid file containing a “situs” address. A situs refers to
the actual address of the property, as opposed to a mailing address. A parcel centroid may be a
graphic digital centorid file or the x and y coordinates recorded in a data file. Centroids of all
types of parcels maybe used including both vacant and improved property. Another type of
source point address data is an address point data file that contains an x,y coordinate and an
address record for every address in a community.
The addresses associated with the centroids or the address point file must be standardized to a
degree. There should be some logical type of formatting for the address components, such as one
field for each of the following: house number, street direction, street name and street type. The
street name portion of the record must be consistent from record to record. For example, all
address points or centroids located on Dearborn Street must have Dearborn spelt the same way
and not Dearbome or Deerbom. Most of these naming convention errors can be cleaned up by
creating a standard address name table and comparing the file against it. The file may also be
parsed using one of the many commercially available software packages. All records with partial
information must be corrected or purged from the file. For example, records with a blank house
number or blank street type will create false address ranges if allowed to remain in the file.
The file containing the street record or centerline file must follow similar restrictions before
input. Principally the street name portion of the data record must be of an identical format to the
street name portion in the centroid or address point file. Therefore, if one file has an item
description for the street name of 20 bytes and character type, then both files must have the same
format of 20 bytes and character type. The centerline files must be scrubbed for completeness.
Every effort must be made to assign a street name direction and type to each graphic element.
Any street segments that will not have abutting addressable features, such as interstates, limited
access highways and access ramps, may be temporarily removed from the file.
If all conditions are met for both of these files, then processing may begin for automatic address
range assignment.
