Midway Island (USA Trust) Site History

History Summary

Station Midway
Country USA Trust
Latitude 28° 13.0' N
Longitude 177° 22.0' W
GLOSS No 106
Time Reference GMT (hours 00-23)
Contributor US Coastal Geodetic Survey (1947-1972)
National Ocean Service (NOS) (1973+)
National Ocean. and Atmos. Administration (NOAA)
Instrument Type Standard mechanical (1947-1974);
Analog-to-digital (ADR) recorder (1975-1991);
Aquatrak acoustic gauge, NOAA Next Generation
Water Level Measuring System (NGWLMS) (1992-2000)
Site of Gauge  
Observational Periods 1947 - 2000

Reference Level

All heights have been referred to the station tide staff zero which is linked to fixed benchmarks.

Tide Gauge Benchmark (TGBM) Description

Benchmark 21(1959), the primary benchmark (PBM) is stamped '21 1959' and is set in a concrete manhole structure at the north east corner of Inner Harbor Boat Basin.

Auxiliary Benchmarks

9 additonal benchmarks are levelled to the TGBM and the Tide Station on a yearly basis.

Benchmark Relationships

TGBM is 10.64ft above Tide Gauge Zero (Station Datum).

NOAA Chart Datum (MLLW) is 2.62ft above Station Datum.

Mean Sea Level (1960-1978) is 3.27ft above Station Datum.

Quality Assessment

Comments

Large fluctuations during November - April for most years are associated with meteorological events. Step-function signatures in the hourly residuals suggest level shifts on 27 September 1968 and on 01 August 1974. However, the mean level and differences with the PSMSL holdings have not warranted an adjustment.

The data for 1996-2000 were supplied with heights relative to MLLW. Consequently 799mm was added to refer the data to tide gauge zero.

The data for 1998-2000 were supplied in non-GMT format and had to be shifted into GMT.

Notable episodic events:

Gaps in the Data Record

The following gaps occur in the data set.

Year CI (%) Missing Data Replaced Gaps or Bad Data Questionable
Fluctuations
    (06)189-(19)189    
1948 86 315-366 None None
1949 76 1,152-186,190-234,238-244 (11)119-(10)120 None
1950 77 92-174 None None
1951 100 None None None
1952 95 95-115 None None
1953 100 None None None
1954 100 None None None
1955 96 351-365 None None
1956 99 1-6 None None
1957 100 None None None
1958 100 None None None
1959 96 254-261,268-275 None None
1960 88 93-122,162-169,274-281 None None
1961 100 None None None
1962 100 None None None
1963 92 213-244 None None
1964 100 None None None
1965 100 None None None
1966 100 None None None
1967 100 None None None
1968 100 None None None
1969 100 None None None
1970 100 None None None
1971 100 None None None
1972 100 None None None
1973 2 1-361 None None
1974 80 1-10,11-32,42-44,45-49,123-125,130-165 (08)035-(00)036,(15)188-(09)189,(11)189-(18)189 None
1975 93 62-86,154-155,155-156 (06)153-(12)153,(17)158-(09)159 271-272,305
1976 61 7-9,52-54,55-64,92-126,141-231,317-319 (08)037-(03)038 None
1977 90 214-248 (11)305-(04)306 None
1978 77 231-233,244-262 (10)091-(22)091 None
1979 67 244-246 None None
1980 89   None None
1981 95 148-168 None None
1982 90 60-97 None None
1983 100 None None None
1984 100 None None None
1985 82 153-219,317 None None
1986 100 None None None
1987 100 None None None
1988 100 None None None
1989 100 None None None
1990 100 None None None
1991 93 114-139 None None
1992 100 None None None
1993 100 None None None
1994 100 None None None
1995 100 None None None
1996 100 None None None
1997 100 None None None
1998 100 None None 1-88,300-301,311-317,342,348-355,360-365
1999 100 None (17)019,(00)331,(06)331,(05)344,(17)351 1,5,19-20,33,57,68,78,83-84,320-321,330-332,337,340,352-355,364-365
2000 100 None None 49-50,83,295