E: The Vertical Control database has recently been migrated to an Access platform. Updates were unavailable to the previous database platform. There may be incomplete or out of date records. The information presented will be updated as current information becomes available. The database was migrated to Access to allow updates and placement of the database on the County of San Diego WEB page. Bench Mark update cards are available in the Survey Records Section of the Department of Public Works, County of San Diego. Survey Records is located at the County Operations Center Annex, 5201 Ruffin Road, Project and Permit Processing.
Vertical control search will be limited to the United States Geological Survey (USGS) Quad sheets. We will be working to bring the full functionality of the Access database to the Web site.
There have been extensive changes and additions to the Bench Mark Data since the publication of Vertical Control Data by the County Engineer Department in 1971 and again by the Department of Public works in 1988.
An important addition to the listing is about 100 miles of first order level lines run in 1978 as part of the Southern California Releveling Project (SCRP). The project data was adjusted by the National Oceanic and Atmospheric Administration (N.O.A.A.).
Precise levels are run following established N.O.A.A. and United States Geodetic Survey (U.S.G.S.) techniques using the Wild N-3 Precise Level and invar precision leveling rods.
The "Super Bench Mark" is an improved and less expensive precise level monument, which consists of a string of coupled, 5/8" diameter, copper-steel rods driven to refusal for stability and capped with a standard brass disk.
Included in this listing are many bench marks established by other agencies, but they are all based on the same
Datum. All N.O.A.A. and U.S.G.S. Bench Marks which have been received by the County, except some in the City of San Diego, are listed.
These County vertical control data books do not contain all elevation control developed by utility districts, the County Water Authority, the State Division of Highways, cities and private engineers. A great amount of data is compiled in the Horizontal and Vertical Control publications of the City of San Diego.
Experience indicates that some bench mark elevations are changed somewhat by soil subsidence, expansion or seismic action. As new circuits are completed, readjustments of older circuits may be necessary.
The arrangement, indexing, and use of contents in these new listings are the same as in the previous publications. Also, the new listings retain the entire content of previous listings which may therefore be discarded.
The users of this book are invited to assist in its maintenance by notifying the County Department of Public Works, Surveying Section, of cases of obliteration, apparent mistakes in description of elevations, and disturbance of bench marks.
The Datum of the majority of the benchmarks is the National Geodetic Vertical Datum of 1929. (NGVD 29) As National Vertical Datum 1988, (NVD 88’) become available, they will be included in this database.
Horizontal Control information maybe obtained through the Survey Records Section. A portion of this Horizontal data is available on line at the following site, WWW.SANGIS.ORG. Access the interactive map section for various types of information including a horizontal control layer.
DATUM: THE NATIONAL GEODETIC VERTICAL DATUM OF 1929
T A B L E O F C O N T E N T S