QUALITY ASSESSMENT OF SEA LEVEL DATA by the UH SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER JOINT ARCHIVE FOR SEA LEVEL updated: 06 Dec 2001 Station : Diego Garcia-C Latitude: 07 17.4S Country : United Kingdom Longitude: 072 23.6E JASL # : 104C Time Meridian: 90E (GMT + 6 hr) GLOSS # : 026 Originator #:2431000 NODC #: 30077202 Contributor : UH Sea Level Center 1000 Pope Rd. MSB 317 Honolulu, Hawaii 96822 ==> And for 1992 onward National Ocean Service (NOS) National Ocean. and Atmos. Administration (NOAA) N/OES22 SSMC4, STATION 7109 1305 East West Highway Silver Spring, MD. 20910-3233 Originator : UH Sea Level Center in collaboration with Naval Oceanographic Command Detachment F. P. O. San Fransisco, CA 96885-2905 Original Data: digital Instrmnt Type: 1) Fischer and Porter Analog-to-Digital Recorder (ADR) 1988-1993 2) Aquatrak acoustic gauge, NOAA Next Generation Water Level Measuring System (NGWLMS) (1992-) Digitzd Intvl: 15 minutes (ADR); hourly and six minute (NGWLMS) Present Data : Hourly, daily, and monthly values obtained by: Hourly : 1) Three-point Hanning filter centered on the hour (ADR and NGWLMS for 1996-) 2) Spot hourly (NGWLMS 1992-1995) Daily : 119-point convolution filter (Bloomfield, 1976) centered on noon applied to the hourly data with respective periods of the 95, 50, and 5% amplitude points at 124.0, 60.2, and 40.2 hours Monthly: Simple average of all daily values; calculated if 7 or fewer days are missing Span of data : 01 Mar 1988 - 31 Dec 2000 Gaps > 1 mon : 01 May 1990 - 21 Jun 1990;13 Oct 1991 - 25 Nov 1991 02 Feb 1994 - 18 Apr 1994;28 Jan 1996 - 07 Apr 1996 11 Jun 1996 - 31 Dec 1996;10 May 1998 - 22 Jun 1998 14 Jul 1998 - 04 May 1999 Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 Units : millimeters Missing Data Flag : 9999 Existing : Yes Operational : Yes Sat. Trans. : Yes Distribution : 1988-2000 Refernce Levl: Heights are referred to the station tide staff zero, which is linked to land-based benchmarks. This reference zero is unique to this station and is not an official datum (chart, national, etc.) and is not relative to local tidal parameters, such as mean lower low water. See the Originators for benchmark descriptions, maps, and the geodetic levelling history. An overlap from 1992 to 1994 between the ADR and NGWLMS was used to link the series. The correction factor of -31.06 feet is added to the NGWLMS to maintain the historic UHSLC datum. Comment : The daily and monthly means do not reveal any reference level shifts or trends. NGWLMS data primary data source beginning in 1992. Gaps filled with ADR data through 1993. CI MISSING REPLACED GAPS QUESTIONABLE YEAR (%) DATA OR BAD DATA FLUCTUATIONS ---- --- -------------------- --------------- -------------------- 1988 78 140-143,226-230, none none 275-288 1989 100 none none 229-231,318,349,362 1990 91 121-172,201-229, none 13-14,58-59,87,144- 263-270,281-286 146,279-280 1991 82 62-69,70-72,154-155, (03)161-(00)162 none 192-197,220-221,246- 247,286-329,353-357 1992 100 none none none 1993 100 none none none 1994 80 33-108 none none 1995 88 23-31,131-141,254- none none 261,275-293 1996 21 1-15,28-98,138-141, none none 163-366 1997 88 1,12-18,180-182,225- none none 230,299-307,320-335, 349-363 1998 29 19-25,39-60,75-83, none none 102-115,130-173, 195-365 1999 66 1-124 (00)165-(23)165 none 2000 100 none (08)066-(00)067 none