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U.S. Geological Survey Open-File Report 2011-1127

Construction of a 3-Arcsecond Digital Elevation Model for the Gulf of Maine


Conversion Factors

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Length
centimeter (cm) 0.3937 inch (in.)
millimeter (mm) 0.03937 inch (in.)
meter (m) 3.281 foot (ft)
meter (m) 1.094 yard (yd)
kilometer (km) 0.6214 mile (mi)
kilometer (km) 0.5400 mile, nautical (nmi)
Area
square kilometer (km²) 0.3861 square mile (mi²)
square meter (m²) 10.76 square foot (ft²)

Resolution

Angular measurement Degrees Approximate meters at equator*
1 arc-second 0.0002777 30
3 arc-second 0.0008333 90
1 arc-minute 0.0166666 2000

One arc-second (1/3,600 of 1 degree (°)) is 1/60th of 1 minute of arc, where a 1 minute of arc is equal to 1/60th of 1°.

* The approximate meters at the equator correspond to measurements made at the equator. Spacing does not correspond to uniform distances between points on the surface of the Earth. Meridians of longitude converge at the poles, which causes the spacing between data points along a parallel of latitude to decrease as one moves north or south away from the equator. The spacing along a meridian of longitude is nearly constant and varies only slightly with the curvature of the Earth.

Frequencies of sidescan sonar and multibeam bathymetry are measured in kilohertz (kHz; 1,000 periods per second). Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88). Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83). Altitude, as used in this report, refers to distance above the vertical datum.

 

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