| Fill in any known line of values and click the "<-
Calculate" button to complete the other lines. Since GPS readings can
be accurate only to 5-15 feet, I have assumed a recording to the nearest foot. This
means that decimal seconds are rounded to 2 places, minutes to 4
places, and degrees to 6 places. Yes, I know the US is one of only
3 countries in the world that have not adopted the metric system (SI) as a standard. Accuracy
- A minute of latitude [along the great polar circle through Paris] is equal to one
nautical mile, 1852 metres, or 6076.1155 feet. Thus, a second of latitude (6076.1155
divided by 60) is 101+.. feet. A foot is then 0.0098747... of a
second, 0.00016457... of a minute, and 0.0000027429... of a degree. WASS (Wide Area
Surveillance Satellite), WAAS (Wide Area Augmentation System) correction improves the
accuracy, but readings will vary at the same spot due to instrument and datum
variations. Coordinates use different datums: NAD27 (North American Datum of 1927),
NAD83, and the UTM (Universal Transverse Mercator), UPS (Universal Polar Stereographic),
WGS84 (World Geodetic System of 1984). A statute mile is 5,280 feet or
1,609.344 metres.
A minute of longitude, of course, varies in length according to the degree of
latitude. The following is a sampling of longitude lengths for selected latitudes,
beginning in the southern US and working north:
- 30 degrees North, (approximately Houston, Texas) a degree of longitude
is 59.96 statute miles, 5274 feet per minute (almost equal to a statute mile), 88
feet per second.
- 35 degrees North, (approximately Albuquerque, New Mexico) a degree of
longitude is 56.73 statute miles, 4992 feet per minute, 83.2 feet per
second.
- 40 degrees North, (Kansas/Nebraska border), a degree of longitude is
53.06 statute miles, 4669 feet per minute, 77.82 feet per second.
- 45 degrees North, (Montana/Wyoming border), a degree of longitude is
49.00 statute miles, 4312 feet per minute, 71.87 feet per second.
- 49 degrees North (US/Canada national boundary), a degree of longitude
is 45.40 statute miles, 3995 feet per minute, 66.59 feet per second.
- 50 degrees North (approximately Powell River, BC, Medicine Hat,
Alberta, and Winnipeg, Manitoba), a minute of longitude is 44.55 statue miles, 3920 feet
(1195 meters) per minute, 65.34 feet (19.9 meters) per second.
- 55 degrees North (approximately Ketchikan, Alaska and Dawson Creek, BC)
a degree of longitude is 39.77 statute miles, 3500 feet (1066.8 meters) per minute, 58.33
(17.78 meters) per second.
- 60 degrees North (southern border of the Northwest Territories), a
degree of longitude is 34.67 statute miles, 3051 feet (930 meters) per minute, 50.85
feet (15.5 meters) per second.
|