Accuracy of programs for predicting Earth tides and ocean loading  

Authors / CoAuthors

Tracey, R.M.

Abstract

The force of gravity at any point on the earth's surface can vary by as much as 300 microgals (1 microgal = 1x10-8 m/s2) over a 6 hour period due to the gravitational attraction of the sun and the moon as they move in relation to the earth. This variation in gravity is called the earth tide. The earth tide is made up of the body tide, which is the direct gravitational effect of the sun and the moon; and the ocean load tide, which is the effect of the shifting mass of the earth's oceans also due to the sun and the moon. Comparison of five tidal prediction computer programs, two of which attempt to model the ocean load tide, with superconducting gravimeter observations at Mt Stromlo, ACT, has found that they all predicted the earth tide to within 6 microgals standard deviation of the observed tidal variation. The two programs that used an ocean tide model predicted the earth tide to better than 1.2 microgals standard deviation. Tidal gravity observations made at Sydney, Parkes and Cobar in NSW, and at Mt Stromlo in the ACT, were compared with predicted earth tides to determine the accuracy of these predictions, particularly for the ocean load tides, at both coastal and inland sites. All of the computer programs tested are capable of predicting the earth tide to sufficient accuracy for most relative gravity applications, such as for exploration purposes. Where accuracies of better than 10 microgals are required, such as with a portable absolute gravimeter or precise microgravity surveys, a program that uses a global ocean tide model is necessary. If better than 5 microgals accuracy is required, such as with precise absolute gravity measurements, a global ocean tide model is not sufficient and one that better suits the local region is required.

Product Type

nonGeographicDataset

eCat Id

63741

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Keywords

• External PublicationScientific Journal Paper

( Theme )

• gravity

( Theme )

• geophysics

( Theme )

• marine

• AU

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

Publication Date

2005-09-01T00:00:00

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Australian Government Security ClassificationSystem    

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Creative Commons Attribution 4.0 International Licence    

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unknown

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geoscientificInformation

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Unknown

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[-45.0, -9.0, 110.0, 155.0]

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