IV.5 Seven-Digit Street Codes: Local Street Name Validity, Local Group Codes
This section discusses local street name validity, the phenomenon that some street names are valid for only a portion of the street. (In fact, there are even a few New York City streets that do not have a single street name that is valid for the street’s full length.) A street that illustrates the phenomenon of local street name validity is Seventh Avenue in Manhattan. The names 7 AVENUE and SEVENTH AVENUE are valid for the full length of the street. The name ADAM C POWELL BOULEVARD and its various spelling variants (POWELL BOULEVARD, A C POWELL BOULEVARD etc.) are valid only for the portion of the street north of Central Park. The name FASHION AVENUE is valid in the Garment District. The names SAINT VINCENTS SQUARE and ST VINCENTS SQUARE are valid for a portion of the street in the vicinity of the former Saint Vincent’s Hospital.
All of the Geosupport functions that accept street name input, except for Function 1N, perform local street name validation, which verifies whether the input street name is specifically valid for the input location, and if it is not valid, returns up to four aliases of the invalid name that are valid for the given location. Local street name validation is performed automatically when a two-work-area call is made, with no special user action required to invoke it.
If, in a two-work-area call, the input street name is not valid for the given input location, Geosupport takes the following actions:
• The call is rejected with a Geosupport Return Code of ‘50’ and an appropriate Message.
• Up to four locally valid street name aliases of the invalid street name are returned in the WA1 List of Street Names field. (Specifically, the names that are returned are the principal street name of each local street name group that is valid for the given location. The concepts of ‘principal street name’ and ‘local street name group’ are discussed below and in the next Chapter.)
• The Reason Code contains the number of names returned in the List of Street Names.
• For MSW: the WA1 Number of Street Names Field contains the number of names returned in the List of Street Names, in packed decimal format. For COW: the WA1 Number of Street Codes and Names Field contains the number of names returned in character decimal format.
For example, the address 375 7 AVENUE in Manhattan is located south of Central Park, so the street name ADAM C POWELL BOULEVARD is invalid for this address. Therefore, a two-work-area call to Function 1E (for example) with the input address as 375 ADAM C POWELL BOULEVARD would result in a GRC ‘50’ rejection and the return of the locally valid alias street name 7 AVENUE in the List of Street Names. On the other hand, 2019 7 AVENUE is north of Central Park, so 2019 ADAM C POWELL BOULEVARD is a valid address, and is accepted by Function 1E. Similarly, a two-work-area call to Function 2 would reject the intersection of ADAM C POWELL BOULEVARD and WEST 56 STREET with a GRC of ‘50’ and the return of the locally valid alias street name 7 AVENUE in the List of Street Names.
Local Group Codes (LGCs)
Local street name validity is reflected in the sixth and seventh digits of the 10SC, which constitute the Local Group Code (LGC). Street codes are assigned in such a way that two names for a street have the same LGC value if and only if those names are valid for the same portion (possibly all) of the street. Note that if two names are valid for overlapping portions of a street, or one is valid for a subset of the portion where the other is valid, then those names are in different local groups. In order to be in the same local group, names must be valid for exactly the same portion of the street.
Conceptually, the set of all street names for a given street can be viewed as being partitioned into subsets called ‘local street name group’ each group identified by its LGC value and consisting of all the names that are valid for a particular portion (possibly all) of the street. (Most New York City streets only have one local street name group.)
A LGC value is meaningful only relative to its B5SC value. The B5SC identifies the street, and the LGC identifies a local street name group for the given street, that is, the group of all names for the given street that are valid for a particular portion (possibly all) of the street. The B5SC concatenated with the LGC, that is, the first eight bytes of the B10SC, constitute the Borough and Seven-Digit Street Code (B7SC). Two street names have the same B7SC value if and only if they are names for the same street (same B5SC value) and are valid for the same portion of the street (same LGC value relative to the given B5SC value).
Street Name Codes (SNCs)
The final three digits of the B10SC are called the Street Name Code (SNC). Thus, the B10SC consists of the concatenation of the borough code, 5SC, LGC and SNC. The SNC serves simply to serialize the street names within a local group, so that the full B10SC is unique to a specific spelling of a specific street name.
Consider the example of Seventh Avenue in Manhattan. The following is a list of many of Geosupport’s normalized aliases for this street, sorted by B10SC. The dashed lines highlight the four local street name groups.
|STREET NAME||B10SC =||BORO+||5SC +||5SC +||5SC +|
|A C POWELL BOULEVARD||11061001010||1||10610||01||010|
|AC POWELL BOULEVARD||11061001020||1||10610||01||020|
|ADAM C POWELL BOULEVARD||11061001030||1||10610||01||030|
|ADAM POWELL BOULEVARD||11061001040||1||10610||01||040|
|ADAM POWELL JR BOULEVARD||11061001050||1||10610||01||050|
|A C P BOULEVARD||11061001070||1||10610||01||070|
|ADAM CLAYTON POWELL BOULEVARD||11061001090||1||10610||01||090|
|ADAM CLAYTON POWELL JR BOULEVARD||11061001100||1||10610||01||100|
|SAINT VINCENTS SQUARE||11061003010||1||10610||03||010|
|ST VINCENTS SQUARE||11061003020||1||10610||03||020|
All of the names in the above list are aliases of each other, and therefore their B10SCs have the same B5SC value, ‘110610’. The first ten names in the list, A C POWELL BOULEVARD and its nine spelling variants, constitute the group of names valid only for the part of the street north of Central Park; this local group is identified by LGC value ‘01’ and B7SC value ‘11061001’. The name FASHION AVENUE is valid only for the portion of the street in the Garment District, and constitutes the sole member of local group ‘02’. Local group ‘03’ consists of the names SAINT VINCENTS SQUARE and ST VINCENTS SQUARE, which are valid only for a small portion of the street in the vicinity of the former Saint Vincent’s hospital. Finally, the names 7 AVENUE and SEVENTH AVENUE are valid for the entire street and constitute local group ‘04’.