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FAQ: ZIP+4 Centroid Location Code Descriptions for geocoding with Business Analyst

Question

ZIP+4 Centroid Location Code Descriptions for geocoding with Business Analyst

Answer

ZIP centroid codes indicate the quality of two location attributes: Census ID accuracy and positional accuracy. The codes are composed of the following characters:

· The first character is always a “Z” and indicates a location derived from a ZIP centroid.

· The second character indicates Census ID accuracy.

· The third character indicates location type.

· The last character indicates how the location and Census ID were defined. This is provided for completeness and may not be useful for most applications. If the last code is not needed, the width of the Location Code field can be set to three and this last identifier will not be returned.

Second Character - Census ID Accuracy

B - Indicates Block Group accuracy (most accurate).

T - Indicates Census Tract accuracy.

C - Indicates unclassified Census accuracy. Normally accurate to at least the County level.

Third Character - Positional Accuracy

9 - Indicates location based upon a ZIP+4 centroid, which is the most accurate centroid and will normally place the location on the correct block face. For a small number of records, the location may be the middle of the entire street on which the ZIP+4 may fall. See the fourth character for a precise indication of locational accuracy.

7 - Indicates location based upon a ZIP+2 centroid. This location can represent a several block area in urban locations, or slightly larger in rural areas.

5 - Indicates the location of the Post Office that delivers mail to that address, or a 5-digit ZIP Code centroid, or a location based upon locale (city). See the fourth character for a precise indication of locational accuracy.

Fourth Character - Methodology

In practice, there are 23 possible combinations of location codes, one for each methodology type. In the following list, the entire location code is at the end of the description for each methodology.

A - Created via address matching to a single segment. Location is assigned in middle of matched street segment, offset 50’ to the proper side of the street (ZB9A).

a - Created via address matching to a single segment, but the correct side of the street is unknown. Location is assigned in the middle of the matched street segment, offset 50’ to the left side of the street, as address ranges increase (ZB9a).

B - Created via address matching to multiple segments, all segments have the same Block Group. Location is assigned to the middle of the matched street segment with the most house number ranges within this ZIP+4. Location is offset 50’ to the proper side of the street (ZB9B).

b - Same as methodology B except that the correct side of the street is unknown. Location is assigned in the middle of the matched street segment, offset 50’ to the left side of the street as address ranges increase (ZB9b).

C - Created via address matching to multiple segments; all segments have the same Census Tract. The Block Group that represents the most households in this ZIP+4 is returned. Location is assigned to the middle of the matched street segment with the most house number ranges within this ZIP+4. Location is offset 50’ to the proper side of the street (ZT9C).

c - Same as methodology C except that the correct side of the street is unknown. Location is assigned in the middle of the matched street segment, offset 50’ to the left side of the street as address ranges increase (ZT9c).

D - Created via address matching to multiple segments, all segments have the same County. The Block Group that represents the most households in this ZIP+4 is returned. Location is assigned to the middle of the matched street segment with the most house number ranges within this ZIP+4. Location is offset 50’ to the proper side of the street (ZC9D).

d - Same as methodology D except that the correct side of the street is unknown. Location is assigned in the middle of the matched street segment, offset 50’ to the left side of the street as address ranges increase (ZC9d).

E - Created via street name matching (no house ranges available). All matched segments have the same Block Group. Location placed on the segment that is closest to the center of matched segments. In almost all cases, this will be on the mid-point of the entire street (ZB9E).

F - Created via street name matching (no house ranges available). All matched segments have the same Census Tract. Location placed on the segment that is closest to the center of matched segments. In almost all cases, this will be on the mid-point of the entire street (ZT9F).

G - Created via street name matching (no house ranges available). All matched segments have the same county. Location is placed on the segment that is closest to the center of matched segments. In almost all cases, this will be on the mid-point of the entire street (ZC9G).

H - Same as methodology G, but some segments were not in the same County. This methodology is used for less than .05% of the centroids (ZC9H).

I - Created ZIP+2 cluster centroid as defined by methodologies A, a, B and b. All centroids in this ZIP+2 cluster have the same Block Group. Location is assigned to the ZIP+2 centroid (ZB7I).

J - Created ZIP+2 cluster centroid as defined by methodologies A, a, B, b, C and c. All centroids in this ZIP+2 cluster have the same Census Tract. Location is assigned to the ZIP+2 centroid (ZT7J).

K - Created ZIP+2 cluster centroid as defined by methodologies A, a, B, b, C, c, D and d. Location is assigned to the ZIP+2 centroid (ZC7K).

L - Created ZIP+2 cluster centroid as defined by methodology E. All centroids in this ZIP+2 cluster have the same Block Group. Location is assigned to the ZIP+2 centroid (ZB7L).

M - Created ZIP+2 cluster centroid as defined by methodology E and F. All centroids in this ZIP+2 cluster have the same Census Tract. Location is assigned to the ZIP+2 centroid (ZT7M).

N - Created ZIP+2 cluster centroid as defined by methodology E, F, G and H. Location is assigned to the ZIP+2 centroid (ZC7N).

V - Over 95% of addresses in this ZIP Code are in a single Census Tract. Location is assigned to the ZIP Code centroid (ZT5V).

W - Over 80% of addresses in this ZIP Code are in a single Census Tract. Reasonable Census Tract accuracy. Location is assigned to the ZIP Code centroid (ZC5W).

X - Less than 80% of addresses in this ZIP Code are in a single Census Tract. Census ID is uncertain. Location is assigned to the ZIP Code centroid (ZC5X).

Y - Generally indicates a rural or sparsely populated area. Census code is uncertain. Location is based upon the USGS places file (ZC5Y).

Z - Generally assigned for P.O. Box or General Delivery addresses. Census code is uncertain. Location is based upon the Post Office location that delivers the mail to that address (ZC5Z).