U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  6

                                                   PUBLICATION DATE:  06/06/1996
Station ID: 9414290                                SUPERCEDED DATE:   04/21/2003
Name:       THE PRESIDIO, SAN FRANCISCO                       
            CALIFORNIA
NOAA Chart: 18649                                  Latitude:         37° 48.4' N
USGS Quad:  SAN FRANCISCO NORTH                    Longitude:       122° 27.9' W


TO REACH TIDE STATION:  To reach the tide station from the intersection of U.S.
Highway 101 (north) and Lincoln Boulevard (last exit before the Golden Gate toll
plaza), proceed NE on Lincoln Boulevard approximately 0.6 km (1.0 mile) to
Cowles Street, turn left onto Cowles Street and proceed 0.3 km (0.5 mile) to
McDowell Avenue, turn left onto McDowell Avenue and proceed 0.2 km (0.3 mile) to
Crissey Field Avenue, turn left onto Crissey Field Avenue and proceed 0.1 km
(0.2 mile) to a stop sign, turn right and then immediately left onto Mason
street, proceed along the National Parks Service parking lot fence where Mason
Street turns into Hamilton Street, and proceed 0.2 km (0.3 mile) to a parking
lot at the end of the street.  The tide station is located in the 2nd building
on the L-shaped wooden pier formerly owned by the U.S. Coast Guard, now owned by
the National Park Service.


                         T I D A L   B E N C H   M A R K S


                 PRIMARY BENCH MARK STAMPING:  180 1936

MONUMENTATION:           Survey Disk                               VM#:      967
AGENCY:                                                            PID#:  HT0702
SETTING CLASSIFICATION:  Concrete Seawall


The primary bench mark is set in the top of a 0.9-m (3') high concrete seawall
at the NW end of Crissy Field on the Coast Guard property, 15 m (49') east of
the NE corner of the crews quarters building, 6 m (20') south of the south side
of the garage building, and 1.1 m (3.5') north of an angle in the seawall.



                         BENCH MARK STAMPING:  BM 174 1925

MONUMENTATION:           Survey Disk                               VM#:      971
AGENCY:                                                            PID#:  HT0697
SETTING CLASSIFICATION:  Concrete Monument


The bench mark is set in a concrete monument level with the ground inside a
brick circle in the pavement at the center of the Y-junction between Marine
Drive and the road leading SE to Fort Winfield Scott, 38 m (125') west of the
extension of the west edge of the engineer's dock where it crosses Marine Drive,
13.0 m (42.5') SW of a fire hydrant, and 8.7 m (28.5') south of the south edge
of an iron manhole cover.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  6

                                                   PUBLICATION DATE:  06/06/1996
Station ID: 9414290                                SUPERCEDED DATE:   04/21/2003
Name:       THE PRESIDIO, SAN FRANCISCO                       
            CALIFORNIA
NOAA Chart: 18649                                  Latitude:         37° 48.4' N
USGS Quad:  SAN FRANCISCO NORTH                    Longitude:       122° 27.9' W


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  BM 176 1925

MONUMENTATION:           Survey Disk                               VM#:      972
AGENCY:                                                            PID#:  HT0705
SETTING CLASSIFICATION:  Concrete Step


The bench mark is set in the west end of the lowest concrete step at the main
entrance to the porch of the U.S. Army Logistic Control office at #651 Mason
Avenue, 30 m (98') SE of the intersection of Crissy Field and Mason Avenues, 15
m (50') south of the centerline of Mason Avenue, and about 0.2 m (0.7') above
the sidewalk.



                         BENCH MARK STAMPING:  181 1945

MONUMENTATION:           Survey Disk                               VM#:      973
AGENCY:                                                            PID#:  HT0701
SETTING CLASSIFICATION:  Concrete Seawall


The bench mark is set in the top of the NW corner of a seawall at the Fort Point
Coast Guard Station, 62 m (204') west of the inshore end of the Coast Guard
wharf, 46 m (151') NW of a flagpole, 22 m (71') NE of the north corner of
Building S.F. 19.4 (paint shop and storage building), and 1.2 m (4.0') above
grade.



                         BENCH MARK STAMPING:  NO 2 1948

MONUMENTATION:           Survey Disk                               VM#:      975
AGENCY:                                                            PID#:  HT0700
SETTING CLASSIFICATION:  Concrete Seawall


The bench mark is set flush in the top of a concrete seawall, 11.4 m (37.5')
west of the west edge of the engineer's dock, 8.1 m (26.5') NE of the NE corner
of corrugated iron building #985, and about 0.9 m (3.0') above ground.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  6

                                                   PUBLICATION DATE:  06/06/1996
Station ID: 9414290                                SUPERCEDED DATE:   04/21/2003
Name:       THE PRESIDIO, SAN FRANCISCO                       
            CALIFORNIA
NOAA Chart: 18649                                  Latitude:         37° 48.4' N
USGS Quad:  SAN FRANCISCO NORTH                    Longitude:       122° 27.9' W


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  CLARK 1948

MONUMENTATION:           Survey Disk                               VM#:      976
AGENCY:                                                            PID#:  HT0698
SETTING CLASSIFICATION:  Concrete Seawall


The bench mark is set in the top of a concrete seawall, about 549 m (1800') NW
of the Fort Point Coast Guard station, 24.2 m (79.5') west of the west edge of
the engineer's dock, 6.9 m (22.5') NE of the NW corner of corrugated iron
building #985, 3.0 m (10') west of the NW corner of a stucco paint locker
building, and about 1.1 m (3.6') above ground.



                         BENCH MARK STAMPING:  4290 J 1976

MONUMENTATION:           Survey Disk                               VM#:      977
AGENCY:                                                            PID#:  HT2256
SETTING CLASSIFICATION:  Copper Clad Steel Rod


The bench mark is in an elevated beach area midway between the Fort Point Coast
Guard pier and the engineer's dock, 133 m (435') WNW of the west end of the
seawall surrounding the Coast Guard crews quarters, 27 m (89') SW of the
shoreward end of the old seaplane ramp, 18.3 m (60.0') SE of the shoreward end
of the concrete discharge pipe, and 0.8 m (2.5') north of a chain link fence
surrounding U.S. Army Field Maintenance Building #937.  The mark is crimped to a
copper-clad steel rod driven 15 m (48'), encased in a 4-inch diameter PVC pipe,
and marked by a witness post.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  6

                                                   PUBLICATION DATE:  06/06/1996
Station ID: 9414290                                SUPERCEDED DATE:   04/21/2003
Name:       THE PRESIDIO, SAN FRANCISCO                       
            CALIFORNIA
NOAA Chart: 18649                                  Latitude:         37° 48.4' N
USGS Quad:  SAN FRANCISCO NORTH                    Longitude:       122° 27.9' W


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  4290 K 1976

MONUMENTATION:           Survey Disk                               VM#:      978
AGENCY:                                                            PID#:  HT2255
SETTING CLASSIFICATION:  Bedrock


The bench mark is set vertically in bedrock on the south side of Marine Drive,
24 m (79') SSW of the SE corner of National Park Service building #T989, 14.7 m
(48.2') SW of Bench Mark 174 1925, and 2.4 m (8.0') south of the south curb of
Marine Drive.



                         BENCH MARK STAMPING:  BM 175 1925

MONUMENTATION:           Survey Disk                               VM#:     1829
AGENCY:                                                            PID#:  HT0696
SETTING CLASSIFICATION:  Concrete Seawall


The bench mark is set in the seawall near the National Park Service building,
62.2 m (214') NE of Bench Mark 4290 L 1976, 59 m (193') west of the NW corner of
the park service building,  28.9 m (94.8') WNW of the northernmost post of a
pedestrian gate, 6.9 m (22.5') north of the centerline of  Marine Drive, and 0.7
m (2.4') south of the north edge of the seawall.  (Note:  The seawall was
repaired in April 1981 and the elevation of the bench mark was changed after the
repair, but the elevation seems stable since then.)

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  6

                                                   PUBLICATION DATE:  06/06/1996
Station ID: 9414290                                SUPERCEDED DATE:   04/21/2003
Name:       THE PRESIDIO, SAN FRANCISCO                       
            CALIFORNIA
NOAA Chart: 18649                                  Latitude:         37° 48.4' N
USGS Quad:  SAN FRANCISCO NORTH                    Longitude:       122° 27.9' W


                            T I D A L   D A T U M S 


Tidal datums at THE PRESIDIO, SAN FRANCISCO based on:

     LENGTH OF SERIES:      19 YEARS
     TIME PERIOD:           1960-1978
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:   


Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:

     HIGHEST OBSERVED WATER LEVEL (01/27/1983)         =   8.87
     MEAN HIGHER HIGH WATER                     MHHW   =   5.83
     MEAN HIGH WATER                            MHW    =   5.23
     MEAN TIDE LEVEL                            MTL    =   3.18
     MEAN SEA LEVEL                             MSL    =   3.13
     MEAN LOW WATER                             MLW    =   1.13
   * North American Vertical Datum              NAVD88 =   0.14
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (12/17/1933)         =  -2.67

   * NAVD is based on elevations published in Quad 371221, 1993, and NOS
     leveling of 1995. 
North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     180 1936                                   13.24      8.01
     BM 174 1925                                16.65     11.42
     BM 176 1925                                15.99     10.76
     181 1945                                   13.29      8.06
     NO 2 1948                                  14.04      8.81
     CLARK 1948                                 14.08      8.85
     4290 J 1976                                11.18      5.95
     4290 K 1976                                19.31     14.08
     BM 175 1925                                13.84      8.61


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  6

                                                   PUBLICATION DATE:  06/06/1996
Station ID: 9414290                                SUPERCEDED DATE:   04/21/2003
Name:       THE PRESIDIO, SAN FRANCISCO                       
            CALIFORNIA
NOAA Chart: 18649                                  Latitude:         37° 48.4' N
USGS Quad:  SAN FRANCISCO NORTH                    Longitude:       122° 27.9' W


                             D E F I N I T I O N S


Mean Sea Level (MSL) is a tidal datum determined over a 19-year National Tidal
Datum Epoch.  It pertains to local mean sea level and should not be confused
with the fixed datums of North American Vertical Datum of 1988 (NAVD88).

NAVD88 is a fixed datum derived from a simultaneous, least squares, minimum
constraint adjustment of Canadian/Mexican/United States leveling observations.
Local mean sea level observed at Father Point/Rimouski, Canada was held fixed as
the single initial constraint.  NAVD88 replaces NGVD29 as the national
standard geodetic reference for heights.  Bench mark elevations relative to
NAVD88 are available from NGS through the World Wide Web at 
National Geodetic Survey.

NGVD29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded.  NGVD29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads.  NGVD29 was originally derived from a general
adjustment of the first-order leveling networks of the U.S. and Canada after
holding mean sea level observed at 26 long term tide stations as fixed.
Numerous local and wide-spread adjustments have been made since establishment in
1929.  Bench mark elevations relative to NGVD29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at 
National Geodetic Survey.

NAVD88 and NGVD29 are fixed geodetic datums whose elevation relationships to
local MSL and other tidal datums may not be consistent from one location to
another.

The Vertical Mark Number (VM#) and PID# shown on the bench mark sheet are unique
identifiers for bench marks in the tidal and geodetic databases, respectively.
Each bench mark in either database has a single, unique VM# and/or PID# assigned.
Where both VM# and PID# are indicated, both tidal and geodetic elevations are
available for the bench mark listed.

The NAVD88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD88 elevations.
The NAVD88 elevation relationship shown in the table is derived from an average
of several bench mark elevations relative to tide station datum.  As a result of
this averaging, NAVD88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD88 elevations listed for
each bench mark in the NGS database.