On 10 Oct 2003 16:13:24 GMT, "Chuck S." wrote:

Greg Neill wrote:

"Chuck S." wrote in message
...
I'm looking to incorporate the calculation of high and low tides into my
Delphi software. For this I need algorithms telling me how to calculate the
time of high and low tides. Do you know where I can get such algorithms? I
understand it will probably involve complex calculations to find the
position of the sun and moon in relation to the earth and I am prepared for
that.

That will be but the beginning of the ordeal. Much of the
physics of the tides is in the interaction of the water with
the geometry of the coastlines. For example, large bays
cause resonance effects. The Bay of Fundy comes to mind.

I'm not looking to take bay action into account since I will be calculating
what I think are called "land tides". So does high tide for a land mass appear
as soon as the moon is overhead? Or is there a delay of x minutes? What would x
be?

Ocean tides are normally computed by fitting a trigonometric series to
observed tide height data. The periods (or frequencies) of the
trigonometric functions are related to apparent motions of the Sun and
Moon, but no one attempts to determine the state of the tide directly
from the positions of those bodies.

Land tides are so much smaller in magnitude that, so far as I know, no
one has attempted to predict them at all. Given the large local
variations in the properties of the Earth's crust, I would expect the
computation to be done in much the same manner as for Ocean tides,
fitting local observations to a series of periodic functions. Anything
else would be computationally awkward at best.

Al Moore