From MCS4P@watson.acc.virginia.edu Tue May 10 20:16:15 1994 Received: from virginia.edu (uvaarpa.Virginia.EDU) by amazon.evsc.Virginia.EDU (4.1/1.34) id AA27230; Tue, 10 May 94 20:16:14 EDT Message-Id: <9405110016.AA27230@amazon.evsc.Virginia.EDU> Received: from watson.acc.virginia.edu by uvaarpa.virginia.edu id aa11992; 10 May 94 20:16 EDT Received: from watson.acc.Virginia.EDU by WATSON.ACC.VIRGINIA.EDU (IBM VM SMTP V2R2) with BSMTP id 1191; Tue, 10 May 94 20:17:43 EDT Received: from WATSON.acc.Virginia.EDU (MCS4P) by watson.acc.Virginia.EDU (Mailer R2.07) with BSMTP id 2449; Tue, 10 May 94 20:17:43 EDT Date: Tue, 10 May 94 20:17:20 EDT From: MARCIO SANTOS Subject: CONVERSION OF HOG TIDES TO USGS To: JOHN Status: OR CONVERTING RELATIVE TIDAL HEIGHT READINGS INTO USGS 1967 REDUCTION LEVEL Tidal height readings, performed at a staff gauge or automatic tidal station, are usually relative readings (in the sense that all readings are relative to an arbitrarily set "zero" level). Relative readings may be used in tide harmonic analysis and prediction. However, if the data is to be used in coastal environmental studies (tidal flooding frequency, plant zonation boundaries, computation of tidal datums, etc.), then the relative "zero" of the tidal station will have to be tied to a known topographic datum. The correction figures listed below convert relative tidal readings into USGS 1967 reduction level. There are several corrections because a new one is necessary every time the tide recording equipment undergoes maintenance work or replacement. HOG ISLAND Subtract the following figures from the relative tidal data: before September 1993 2.197 September 1993 through January 1994 1.862 February 1994 through October 1994 2.260