On vacation on the east coast, enjoying the beach and seeing the low and high tides. Reading about the tides and lunar effect.. Discussion comes to the effect to the ground surface by the lunar effect. Some of you brainiacs have a better insight. I normally work in the mountains so I feel there is little effect.
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Tides are the confusion of many surveyors and clients alike. NGVD 29 or NAVD 88 or the next set in GRAV-D 2022. In south Florida we get asked all the time about how the elevations are determined and the conversation always seems to end open ended.... Nothing like telling your client their seawall is it elevation 1.2 when the water is only .3 from the lip...
I hope that you made it up to New England on your east coast tour. Our tidal range in Cape Cod Bay is about 10'. It is very dramatic at low tide to see the tidal flats in Brewster extend out for a mile, and then consider that in six hours there will be 5' of water right there 100' in front of you when, at low tide, you can't eve see the water!
Are you asking about Earth Tides?
"Earth tide or body tide is the displacement of the solid Earth's surface caused by the gravity of the Moon and Sun. Its main component has meter-level amplitude at periods of about 12 hours and longer. The largest body tide constituents are semi-diurnal, but there are also significant diurnal, semi-annual, and fortnightly contributions. Though the gravitational forcing causing earth tides and ocean tides is the same, the responses are quite different."
Yep, the ground beneath our feet rises and falls up to 1 1/2 feet regularly in some areas. Due to Earth Tides, the earth also moves horizontally, two inches or so worst case.
Lots of physics and math involved. One precalculus torture is having students model tides with trig functions.
All you really need to know can be found here: [MEDIA=youtube]kZN0KogeV4A[/MEDIA]
