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. 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. 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. Page numbers function as indicators of continuity within an edition only.