Datum Planes
- San
Francisco City Datum is 6.70 feet above ordinary high water mark, which
was formerly on a pile at the Boat House, corner Pacific and Davis Sts.
- USC
and GS Sea level datum of the first order level net 1929 general
adjustment is 8.616 feet below San Francisco City datum. Determined by the City and County
Engineer’s office precise level party interconnecting between USC and GS
bench marks on first order level net and City and County of San Francisco Bench
Marks.(Note – 30 USC and GS BMs used
in making this Field connection)
- USC
and GS determination of City and County of San Francisco Datum = 8.61
feet. (Note - No reference given of how this was determined)
- Mean
sea level at the Presidio primary tide station = sea level datum of the
first order level Net (1929 general adjustment).
This plain is 3.05 feet above mean lower low water at this
tidal station. Mean sea level at
the Presidio primary tide station is 0.08 feet higher than standard sea
level previously used before 1929.
- S.P.R.R.Co.
datum plane is according to S.P.R.R. Co. records 4.735 feet below
S.P.R.R.Co.B.M. at 4th
and Townsend Streets.The
elevation of this BM was determined by the City Engineers precise leveling
in 1900 to be 0.786 below city base. (4.735+0.786= 5.521,San
Francisco Datum is 5.521 feet higher than S.P.R.R.Co.
Datum)
- Spring
Valley Water Co. Base referred to as Crystal Springs Datum and also as
S.F.W.D. Datum was found by precise leveling at University Mound Reservoir
to be 4.984 feet below City of San Francisco Base.
- Berkeley
City Base is 5.873 feet below City of San Francisco Base
- Oakland
City Base is 5.483 feet below City of San Francisco Base
- Alameda
City Base is 5.203 feet below City of San Francisco Base
- S.P.R.R.Co.,
Oakland is 12.283 feet below City of San Francisco Base
- S.P.R.R.Co.,
San Francisco is 5.521 feet below City of San Francisco Base
Mean Sea Level is
8.616 feet below City Datum
Mean Lower Low Water
is 11.666 feet below City Datum