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Bench Mark Sheet for 8417988, GREAT DIAMOND IS., CASCO BAY ME

Superseded Epoch

Large map location marker Station Location
Small red map location marker Published bench mark
Small blue map location marker Unpublished bench mark

Bench mark positions only appear on the map if their coordinates in the CO-OPS database are at the precision of degrees/minutes/seconds/and tenths of seconds. If the coordinates are less precise, the mark will not appear.

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  5

                                                                                
Station ID: 8417988                         PUBLICATION DATE:  05/20/2004
Name:       GREAT DIAMOND IS., CASCO BAY                      
            ME
NOAA Chart: 13290                           Latitude:   43° 40.2' N (  43.67000)
USGS Quad:  PORTLAND EAST                   Longitude:  70° 12.0' W ( -70.20000)


To reach the tidal bench marks from South Portland, Maine, proceed by boat to
the State of Maine Ferry Pier, located on the south side of Great Diamond
Island, in the SW section of Casco Bay.  The bench marks are located near the
Ferry Pier and extend NE along the dirt road.  The tide gage and staff were
located on the north side of the pier.


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


                 PRIMARY BENCH MARK STAMPING:  841 7988 A 1979
                         DESIGNATION:          841 7988 A TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         1915
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Rock ledge                            OPUS PID:        
LATITUDE:   43° 40.2' N (  43.67000)          LONGITUDE:  70° 12.0' W ( -70.20000)


The primary bench mark is a disk set flush in a rock ledge to the NW of the
State Ferry Pier, 12.0 m (39.4 ft) west of the centerline of the Ferry Pier, 5.8
m (18.9 ft) west of the west side of a wooden house located at the north end of
the pier, and 5 m (15 ft) east of the shoreline.



                         BENCH MARK STAMPING:  841 7988 B 1979
                         DESIGNATION:          841 7988 B TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         1916
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Rock ledge                            OPUS PID:        
LATITUDE:   43° 40.2' N (  43.67000)          LONGITUDE:  70° 12.0' W ( -70.20000)


The bench mark is a disk set flush in a rock ledge on the west side of the dirt
road, north of the pier, 30.2 m (99.2 ft) north of bench mark 841 7988 A 1979,
11.7 m (38.5 ft) east of the shoreline, 5.2 m (17.0 ft) west of the centerline
of the dirt road.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                                                
Station ID: 8417988                         PUBLICATION DATE:  05/20/2004
Name:       GREAT DIAMOND IS., CASCO BAY                      
            ME
NOAA Chart: 13290                           Latitude:   43° 40.2' N (  43.67000)
USGS Quad:  PORTLAND EAST                   Longitude:  70° 12.0' W ( -70.20000)


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


                         BENCH MARK STAMPING:  841 7988 C 1979
                         DESIGNATION:          841 7988 C TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         1917
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Rock ledge                            OPUS PID:        
LATITUDE:   43° 40.2' N (  43.67000)          LONGITUDE:  70° 12.0' W ( -70.20000)


The bench mark is a disk set flush in a rock ledge outcropping east of the dirt
road which leads to the pier, 16.0 m (52.5 ft) north of the shoreline, 12.0 m
(39.5 ft) east of the centerline of the dirt road, 0.8 m (2.7 ft) north of the
centerline of the rampway leading to a small boat dock.



                         BENCH MARK STAMPING:  841 7988 D 1979
                         DESIGNATION:          841 7988 D TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         1918
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Rock outcropping                      OPUS PID:        
LATITUDE:   43° 40.2' N (  43.67000)          LONGITUDE:  70° 12.0' W ( -70.20000)


The bench mark is a disk set flush in a rock outcropping, in the front yard of
the Noring family residence, a red cedar shingle two story house, 0.20 km (0.12
mi) north, up the dirt road from the pier, 25.1 m (82.5 ft) north of the NW
corner of the Noring residence, 22.0 m (72.2 ft) north of bench mark 841 7988 E
1979, 10.1 m (33.0 ft) west of the power pole in the front yard of the Noring
residence.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                                                
Station ID: 8417988                         PUBLICATION DATE:  05/20/2004
Name:       GREAT DIAMOND IS., CASCO BAY                      
            ME
NOAA Chart: 13290                           Latitude:   43° 40.2' N (  43.67000)
USGS Quad:  PORTLAND EAST                   Longitude:  70° 12.0' W ( -70.20000)


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


                         BENCH MARK STAMPING:  841 7988 E 1979
                         DESIGNATION:          841 7988 E TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         1919
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Rock outcropping                      OPUS PID:        
LATITUDE:   43° 40.2' N (  43.67000)          LONGITUDE:  70° 12.0' W ( -70.20000)


The bench mark is a disk set flush in a rock outcropping in the front yard of
the Noring residence, a red cedar shingle two story house, 9.4 m (31.0 ft) NW of
the NE corner of the Noring house and 3.1 m (10.3 ft) NE of the NW corner of the
house.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                                                
Station ID: 8417988                         PUBLICATION DATE:  05/20/2004
Name:       GREAT DIAMOND IS., CASCO BAY                      
            ME
NOAA Chart: 13290                           Latitude:   43° 40.2' N (  43.67000)
USGS Quad:  PORTLAND EAST                   Longitude:  70° 12.0' W ( -70.20000)


                            T I D A L   D A T U M S 


Tidal datums at GREAT DIAMOND IS., CASCO BAY based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           September 1979 - September 1979
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8418150 PORTLAND, CASCO BAY


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

     MEAN HIGHER HIGH WATER                     MHHW   =  3.006
     MEAN HIGH WATER                            MHW    =  2.875
     MEAN SEA LEVEL                             MSL    =  1.502
     MEAN TIDE LEVEL                            MTL    =  1.491
     MEAN LOW WATER                             MLW    =  0.107
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     841 7988 A 1979                             3.741    0.866
     841 7988 B 1979                             4.410    1.535
     841 7988 C 1979                             3.548    0.673
     841 7988 D 1979                            12.418    9.543
     841 7988 E 1979                            11.557    8.682


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

                                                                                
Station ID: 8417988                         PUBLICATION DATE:  05/20/2004
Name:       GREAT DIAMOND IS., CASCO BAY                      
            ME
NOAA Chart: 13290                           Latitude:   43° 40.2' N (  43.67000)
USGS Quad:  PORTLAND EAST                   Longitude:  70° 12.0' W ( -70.20000)


                             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 NGS's Integrated Data Base (IDB PID)
provides geodetic datum based on traditionally leveled and bluebooked ties to
the National Spatial Reference System(NSRS) https://www.ngs.noaa.gov/datasheets/.
The NGS Online Positioning User Service (OPUS PID) provides geodetic datum based
on GPS position & tie it to the NSRS https://www.ngs.noaa.gov/OPUS/.

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.

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Revised: 08/08/2018
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