U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  8

                                                                                
Station ID: 8778490                         PUBLICATION DATE:  02/08/2018
Name:       PORT MANSFIELD                                    
            TX
NOAA Chart: 11306                           Latitude:   26° 33.5' N (  26.55764)
USGS Quad:  PORT MANSFIELD                  Longitude:  97° 25.5' W ( -97.42572)


To reach the tidal bench marks from the the Port Mansfield water tower in town
on Texas Highway 186 (Port Mansfield Drive), proceed east on Texas Highway 186
for approximately 0.3 km (0.2 mi) to the end of the road at Laguna Madre. The
bench marks are located along Texas Highway 186 and in the harbor area. The tide
gauge is on the first fishing pier north of Texas Highway 186 inside a gated
community called Mansfield Point. Station can be accessed by boat or by calling
the local Harbor Office at 956-944-2325.


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


                 PRIMARY BENCH MARK STAMPING:  NO 1 1964
                         DESIGNATION:          877 8490 TIDAL 1

MONUMENTATION:           Tidal Station disk                    VM#:         3100
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:        
SETTING CLASSIFICATION:  Concrete head wall                    OPUS PID:        
LATITUDE:   26° 33.5' N (  26.55889)          LONGITUDE:  97° 25.5' W ( -97.42583)


The primary bench mark is a disk set in a concrete headwall of a small culvert
at the end of State Highway 186 (Port Mansfield Drive), 7 m (23 ft) SE of a
small cottage, 5.00 (16.4 ft) west of the seawall, 1.20 m (3.9 ft) NNW of the
south end of culvert.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  8

                                                                                
Station ID: 8778490                         PUBLICATION DATE:  02/08/2018
Name:       PORT MANSFIELD                                    
            TX
NOAA Chart: 11306                           Latitude:   26° 33.5' N (  26.55764)
USGS Quad:  PORT MANSFIELD                  Longitude:  97° 25.5' W ( -97.42572)


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


                         BENCH MARK STAMPING:  BM NO 2 1964
                         DESIGNATION:          877 8490 TIDAL 2

MONUMENTATION:           Tidal Station disk                    VM#:         3101
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:        
SETTING CLASSIFICATION:  Concrete head wall                    OPUS PID:        
LATITUDE:   26° 33.4' N (  26.55667)          LONGITUDE:  97° 25.7' W ( -97.42831)


The bench mark is a disk set in the SE corner of a headwall for a small concrete
box that serves as an intake for a 14-inch concrete drain midway between a boat
ramp and a warehouse, 59.98 m (196.8 ft) SW of the SW face of the warehouse,
30.00 m (98.4 ft) NW of the seaward edge of the dock, 22.90 m (75.1 ft) north of
a light pole, and 0.21 m (0.7 ft) west of the SE corner of the concrete box.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  8

                                                                                
Station ID: 8778490                         PUBLICATION DATE:  02/08/2018
Name:       PORT MANSFIELD                                    
            TX
NOAA Chart: 11306                           Latitude:   26° 33.5' N (  26.55764)
USGS Quad:  PORT MANSFIELD                  Longitude:  97° 25.5' W ( -97.42572)


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


                         BENCH MARK STAMPING:  LEGION NO 5 1939 1962
                         DESIGNATION:          LEGION RM 5

MONUMENTATION:           Reference Mark disk                   VM#:         3103
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  AB0202
SETTING CLASSIFICATION:  Concrete monument                     OPUS PID:        
LATITUDE:   26° 33.5' N (  26.55889)          LONGITUDE:  97° 25.6' W ( -97.42611)


The bench mark is a disk set in the top of a 0.3 m x 0.3 m (1 ft x 1 ft)
concrete post, 16.50 m (54.1 ft) NW of the centerline of Texas State Highway 186
(Port Mansfield Drive), 6.50 m (21.3 ft) SW of the centerline of White Drive,
1.0 m (3.3 ft) NW of utility pole number 15, 0.50 m (1.6 ft) south of a metal
witness post, and flush with the ground.



                         BENCH MARK STAMPING:  8490 B 1978
                         DESIGNATION:          877 8490 B

MONUMENTATION:           Tidal Station disk                    VM#:         3105
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Concrete retaining wall               OPUS PID:        
LATITUDE:   26° 33.4' N (  26.55622)          LONGITUDE:  97° 25.7' W ( -97.42883)


The bench mark is a disk located on the north side of Port Mansfield Harbor on
the west side of the public boat ramp, 15 m (50 ft) north of the east end of the
gas dock at Port Mansfield Marina, 15 m (50 ft) SE of the NE corner of the Port
Mansfield Marina Building, 11.40 m (37.4 ft) east of the SE corner of the Marina
Building, and 6.00 m (19.7 ft) south of the southern side of the steps leading
to the boat ramp.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  8

                                                                                
Station ID: 8778490                         PUBLICATION DATE:  02/08/2018
Name:       PORT MANSFIELD                                    
            TX
NOAA Chart: 11306                           Latitude:   26° 33.5' N (  26.55764)
USGS Quad:  PORT MANSFIELD                  Longitude:  97° 25.5' W ( -97.42572)


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


                         BENCH MARK STAMPING:  8490 D 1990
                         DESIGNATION:          877 8490 D

MONUMENTATION:           Tidal Station disk                    VM#:         3107
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID#: DP0733
LATITUDE:   26° 33.4' N (  26.55719)          LONGITUDE:  97° 25.7' W ( -97.42911)


The bench mark is a disk crimped to the top of a stainless steel rod and encased
in a 4 inch PVC pipe with concrete kickblock.  The bench mark is located 
approximately 274 m (899 ft) SSW of the Port Mansfield water tower, 48 m (159
ft) NE of the centerline of the entrance to the Port Mansfield Marina, 24.1 m
(79.1 ft) ESE of the centerline of Port Mansfield Road, and 23.90 m (78.4 ft)
NNW of a light pole.



                         BENCH MARK STAMPING:  8490 E 1990
                         DESIGNATION:          877 8490 E

MONUMENTATION:           Tidal Station disk                    VM#:         3108
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID:        
LATITUDE:   26° 33.4' N (  26.55689)          LONGITUDE:  97° 25.8' W ( -97.43025)


The bench mark is a disk located 0.5 km (0.3 mi) SW of the the east end of Port
Mansfield Drive, 45.20 m (148.3 ft) NE of a power pole, 32.49 m (106.6 ft) SW of
the SW corner of parking lot, and 0.61 m (2.0 ft) south of a witness post.  The
bench mark is set 3 cm (0.1 ft) below the ground, crimped to the top of a
stainless steel rod driven an unspecified depth, and encased in a 5 inch PVC
pipe with concrete kickblock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  8

                                                                                
Station ID: 8778490                         PUBLICATION DATE:  02/08/2018
Name:       PORT MANSFIELD                                    
            TX
NOAA Chart: 11306                           Latitude:   26° 33.5' N (  26.55764)
USGS Quad:  PORT MANSFIELD                  Longitude:  97° 25.5' W ( -97.42572)


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


                         BENCH MARK STAMPING:  8490 F 1993
                         DESIGNATION:          877 8490 F

MONUMENTATION:           Tidal Station disk                    VM#:        12490
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Stainless steel rod                   OPUS PID:        
LATITUDE:   26° 33.5' N (  26.55897)          LONGITUDE:  97° 25.6' W ( -97.42664)


The bench mark is a disk located at the SW corner of Mrs. Shelton's garage at
201 North Shore Drive, 20.60 m (67.6 ft) NNW of the centerline of Port Mansfield
Drive (Texas State Highway 186), 14.30 m (46.9 ft) west of the SW corner of  the
residence at 201 North Shore Drive, and 0.61 m (2.0 ft) south of the SW corner
of the garage. The bench mark is crimped to the top of a stainless steel rod
driven into the ground, and encased in a 6-inch PVC pipe with concrete
kickblock.



                         BENCH MARK STAMPING:  8490 H 2005
                         DESIGNATION:          877 8490 H

MONUMENTATION:           Bench Mark disk                       VM#:        20548
AGENCY:                  Conrad Blucher Institute (CBI)        IDB PID#:        
SETTING CLASSIFICATION:                                        OPUS PID:        
LATITUDE:   26° 33.5' N (  26.55783)          LONGITUDE:  97° 25.5' W ( -97.42542)


The bench mark is a disk located on seawall bulkhead approximately 38 m (124.7
ft)  NNE of the tide gauge station, 14.5 m (47.6 ft) east of the eastern most
boat slip along the harbor channel, and 6 m (19.7 ft) SSE of the SE corner of
the large beach house in the SE corner of Mansfield Point subdivision, .

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  8

                                                                                
Station ID: 8778490                         PUBLICATION DATE:  02/08/2018
Name:       PORT MANSFIELD                                    
            TX
NOAA Chart: 11306                           Latitude:   26° 33.5' N (  26.55764)
USGS Quad:  PORT MANSFIELD                  Longitude:  97° 25.5' W ( -97.42572)


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


                         BENCH MARK STAMPING:  8490 I 2005
                         DESIGNATION:          877 8490 I

MONUMENTATION:           Bench Mark disk                       VM#:        20549
AGENCY:                  Conrad Blucher Institute (CBI)        IDB PID#:        
SETTING CLASSIFICATION:                                        OPUS PID:        
LATITUDE:   26° 33.5' N (  26.55850)          LONGITUDE:  97° 25.5' W ( -97.42575)


The bench mark is a disk located on a seawall bulkhead approximately 80 m
(262.47 ft)  NNW of 8778490 H, 24 m (78.74 ft) SSE of the first large beach
house on the east side of Mansfield Point, 42 m (137.8 ft) east of the
centerline of the entrance road to Mansfield Point.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  7 of  8

                                                                                
Station ID: 8778490                         PUBLICATION DATE:  02/08/2018
Name:       PORT MANSFIELD                                    
            TX
NOAA Chart: 11306                           Latitude:   26° 33.5' N (  26.55764)
USGS Quad:  PORT MANSFIELD                  Longitude:  97° 25.5' W ( -97.42572)


                            T I D A L   D A T U M S 


Tidal datums at PORT MANSFIELD based on:

     LENGTH OF SERIES:      3 YEARS
     TIME PERIOD:           10/12 - 9/13 , 3/14 - 2/15 , 5/16 - 4/17
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8779770 PORT ISABEL, LAGUNA MADRE


Elevations of tidal datums referred to Mean Sea Level (MSL), in METERS:

     MEAN SEA LEVEL                             MSL    =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                                MSL

     NO 1 1964                                            1.642
     BM NO 2 1964                                         1.872
     LEGION NO 5 1939 1962                                4.086
     8490 B 1978                                          1.682
     8490 D 1990                                          3.403
     8490 E 1990                                          2.898
     8490 F 1993                                          2.356
     8490 H 2005                                          1.895
     8490 I 2005                                          1.929


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  8 of  8

                                                                                
Station ID: 8778490                         PUBLICATION DATE:  02/08/2018
Name:       PORT MANSFIELD                                    
            TX
NOAA Chart: 11306                           Latitude:   26° 33.5' N (  26.55764)
USGS Quad:  PORT MANSFIELD                  Longitude:  97° 25.5' W ( -97.42572)


                             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.