The bench mark numbering system is based upon a grid superimposed over the City (see Index Map).

An index map showing the leveling lines and street names is provided for each area. These maps are not to scale and show only streets along which bench marks occur. It is helpful to use a street map in conjunction with them.

The index is arranged in numerical order of the bench mark numbers.

Each bench mark is given a seven digit number. The first two digits represent the number of the grid area, the last five are assigned in sequence along leveling lines, usually streets, leaving gaps for insertion of additional or replacement bench marks. The limits of the sequence are shown by arrows. The ranges of the sequence are printed between the delimiting arrows.

A bench mark at the intersection of leveling lines will be found in the sequence(s) of numbers noted on one or more leveling lines. Occasionally a single bench mark will not be in a sequence and its number is shown on the index map at its approximate location.

Bench mark information is retrievable by bench mark number or by description in conjunction with the index maps. Descriptions are on the left side of each page with corresponding numbers at the extreme right. Descriptions pertaining to bench marks of other agencies are not necessarily identical to those published by the other agency. Abbreviations are listed and defined at the end of this section.

Notes pertaining to the status or physical condition of a bench mark may follow the descriptive text enclosed in asterisks. A bench mark that replaces a gone or abandoned one but is not in the identical location is regarded as a new bench mark and is assigned a new number. A bench mark number is never reassigned to a new bench mark or to a different bench mark.

When a bench mark is reset in the same horizontal location, it will retain its original number and a note enclosed in asterisks will indicate it as "RESET".

When referring to a bench mark its number AND description should be used.

The latest elevations appears immediately to the right of the description. Each elevation is shown in feet to three decimal digits and under each elevation in parentheses is the elevation in meters to the three decimal digits. The elevation shown in feet is suffixed by a number representing the basis year of the elevation. In addition, there may be a letter (i.e., A, C, R, S) following the year. This suffix serves to differentiate the results of periodic releveling and to correlate elevations which are mutually consistent, and is not necessarily the year in which observations were made. Specific information regarding the date of observation and/or adjustment may be obtained from the Geodetic Section.

A minus sign preceding the elevation indicates a below sea level bench mark.

Once a bench mark has a history of five published elevations each releveling causes the oldest elevation to be dropped from subsequent editions. Complete histories are available at the Geodetic Section.

The results of special leveling surveys in subsidence areas are published in separate form. This information is available upon request in the Geodetic Section.

Page numbers are printed in the upper left corner of each sheet and four digit edition numbers are printed in the lower right corner. This number represents the date of machine tabulation. (The first pair is the month, the second pair is the year). Page numbers function as indicators of continuity within an edition only. Page numbers and edition numbers should not be used when referring to a bench mark or the index.