One of the most often asked questions about the geocoding results is what is the difference between S3 and Z3 result codes. An S3 match is defined as a single close match with the point located at the Secondary Postal Code centroid. The Z3 match is also spotted at the Secondary Postal Code centroid. The difference is in how the geocoding service arrives at the results.
An S3 result code indicates that the geocoding service found a street address that matches, but the match record did not contain any street geometry (line points). geocoding service is, therefore, unable to interpolate where along the segment to place the record. The best it can do is to place it at the Secondary Postal Code centroid.
A Z3 match, on the other hand, is a direct match to the Secondary Postal Code centroid. In this case, the geocoding service could not find a street address match for one of several reasons:
- The request is a Postal Code Centroid
- There was no close match and your fallback criteria to Postal Code Centroid
- The address is a P.O. Box or rural route
On a map, the S3 and Z3 records display at the same location, assuming the input Postal Codes were the same for both records. However, the matching process for an S3 record has an extra step that could place the point at a different, and more accurate, Secondary Postal Code centroid. During a street address match, geocoding service corrects the input Postal Code if the match record includes different information. Z3 matches do not get corrected. Because of this correction step, the S3 match is considered the more precise match.
Figure: Envinsa Postal Code Parsing Example
Figure: MapMarker Postal Code Parsing Example
