Tidal Datum

1. In general, a datum is a base elevation used as a reference from which to reckon heights or depths.
2. Wikipedia: Datum, NAVD
3. A tidal datum is a standard elevation defined by a certain phase of the tide.
4. Tidal datums are used as references to measure local water levels and should not be extended into areas having differing oceanographic characteristics without substantiating measurements.
5. In order that they may be recovered when needed, such datums are referenced to fixed points known as bench marks.
6. Tidal datums are also the basis for establishing privately owned land, state owned land, territorial sea, exclusive economic zone, and high seas boundaries.

Source: Tidal Datums

1. Township saves Elevation Certificates
2. Garage floor is 6', see here
3. per this tide datum is different than NAVD as tide heights is a function of latitude of location
4. Tide rises and drops only a foot in floria and 14 feet in parts of maine
5. Learn about National Geodetic Survey Benchmark
6. See Data Sheet, and data format
7. To Convert from NGVD29 to NAVD88, subtract 1.18( Lee County, FL) feet from the elevation listed.
8. Vertical Transformation

1. Station St. Petersburg, FL
2. Click Datums under Tides/Water Levels
3. Zero is MLLW, NAVD88 is 1.48, MLW .39, MLW-NAVD = -1.09
4. MHW=1.98, MHW-NAVD = 0.50

1. Station Clearwater Beach FL
2. Click Datums under Tides/Water Levels
3. Zero is MLLW, NAVD88 is 1.79, MLW .51, MLW-NAVD = -1.28
4. MHW=2.40, MHW-NAVD = .61

1. Land Boundary Information System.
2. Also Datum, Survey, MHW

1. See Tide station
1. Indian Rocks report, Station 872-6601, MLW: -1.21 NAVD88
2. John's Pass report, Station 872-6533, MLW: -0.99 NAVD88
2. MHW Survey index
1. Township 30, Range 15, Section 31, Boca Ciega Bay
2. MHW: 1575, EL A: 1.17, EL B:1.73, EL C: .56,
3. Date 6/17/1996, NAVD not specified

1. I am not sure about significance of MLW yet except the dredging company used it.
2. MLW is -1.11 NAVD88 for my home as per labins. He uses it for all over FL.
3. measured seawall at NAVD 3.89'
4. hence my seawall is 5' above MLW
5. I am not sure how we get -1.11 yet, asked Kevin