GEO 311 - November 6, 2007

Tidal Energy

• Long Island Estuaries GIS Data
• Prospective Sites for Tidal Energy Products (.xls) - derived from http://wwwphys.murdoch.edu.au/rise/reslab/resfiles/tidal/text.html

Some Useful Numbers

• g (acceleration due to Earth's gravity) = 9.8 m/s²
• density of seawater = 1030 kg/cm³
• 1 mile² = 2.59 km²
• joule (J) = kg m²/s²
• watt (W) = J/s

Calculating Areas (in square meters) of Polygons in the Long Island Sound Shapefile Using ArcGIS

Open the attribute table of the polygon layer.

Use the options menu to create an Area field.

The type for the field should be double.

For precision, which is the length of the field, use 10.

For scale, which is the number of decimal places, use 1 .

Right-click heading for the Area field and choose calculate values...

Check advanced.

In the "Pre-Logic VBA Script Code" text area, enter:

Dim dblArea as double
Dim polyArea as IArea
Set polyArea = [shape]
dblArea = polyArea.area

In the "Area =" text field, enter:

dblArea

Click OK

Links to Additional Information

• Newsday: Energy firms eye LI Sound, Rival companies propose to generate electricity by submerging turbines off the North Fork
• Tidal Energy Systems
  • Excel Spreadsheet derived from above link
• Wikipedia: Tidal Power
• The Long Island Sound Study
• Geologic History of Long Island Sound
• Connecticut DEP - Long Island Sound Facts
• Long Island Sound - New York State Tides