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| Solar Flare, March 6, 2012 |
If we were out in the middle of sea and the GPS stopped working, could we find our way around? I better hope so.
We know that if a war begins, GPS would be the first to go. But what if a Solar flare knocks out power for a while, lightning strikes the mast (knock on wood), or GPS is stolen, learn the basics and repeat until it is second nature.
Remember about a decade ago (prior to May 2000), we had to get the daily correction for GPS, selective availability. Now our airplanes, boats, and cars have become too dependent upon GPS. It is a convenience that we should not become too dependent upon. Learn the basics: we did this in college with my degree, and it is crucial that we continue.
- Solar Flares knocks out GPS signals.
- Understanding Dead Reckoning.
Why are there three different miles (nautical mile, statute mile, international mile)?
- Nautical mile (M) is based on one minute of arc that was agreed upon Internationally, based on this idealized Earth, using the average of one minute of arc, from both equatorial and polar planes (since 1 degree = 60 minutes). 360° x 60' = 21600' minutes. Arc minute along the equatorial circumference (24,901.55 mi/21600' * 5280 ft/mi = 6087 ft/'), but Arc minute along the polar circumference (24,815 mi/21600' * 5280 ft/mi = 6066 ft/'). The average is 6076.115486 ft (international) =(1/0.3048)* 1852. The mean sea mile and geographic mile all means the same as the nautical mile. 1 nautical mile (M) = 1,852 m. M was chosen as the abbrev. to prevent confusion of nanometer (nm).
- US Statute mile is only any area within the boundary of US land. It is based on the 1893 definition of US survey foot (any foot derived from geodetic surveys within the USA = 1200/ 3937 meters. Agreed that it would only be for the US in the international agreement in 1959 Standard for Measurement held in Monaco. That is why the ICW (or GIWW) is in statute miles.
- International mile (1 mi = 1609.344 meters) was agreed upon at the 1959 Standard for Measurement to be based on 1 ft (international)= 0.3048 m. The difference between statute mile and international mile may be only 0.0002%, but when spread over great distance can be hundreds of miles off.
- Well we all know about the 3 mile discharge rule. But did you know that Texas waters extend for 9 nautical miles (from the 1975 law) (from the Rio Grande to the Sabine River).
- From 1999 the law was change to extend between 12 - 24 nautical miles from the shoreline. It differs by area.
Know how to find the distance between two positions using latitudes, longitudes, nautical miles, time.
- Click link for distance charts between 2 US ports
Here are some formulas and a pdf to download to help out.
Knot = nautical miles an hour
- 1 nautical mile (M) = mean 1 minute (1') arc = 6076.115486 ft (international)= 6076.103 ft (US survey) = 1.150779 mi (statute) = 1,852 m
- 1 mi (international) = 0.999 998 * mi (statute) = 1,609.344 m = 8 furlongs
- 1 mi (statute) = 5280 ft (survey) = 1609.347218694 m = (5280 x 1200/3937) m
- 1 ft (international)= 0.3048 m
- 1 ft (US survey)= 0.30480060960125017024227597156924 m = 1200/3937 m
- other navigation info
History of our Coastal Zone measurements
- 1999: Contiguous Zone: ranging 12 nautical miles (M) to 24 M offshore
- 1988: US Territorial Sea limit: 12 nautical mile (used to be 3 M) offshore
- 1975: Texas Coastal Management Program extends 9 nautical miles
- 1959: Internationally agreed Standard for Measurements, plus US survey foot (any foot derived from geodetic surveys within the USA = 1200/ 3937 meters) enacted from U.S. Metric Law of 1866 (defined 1893). International nautical mile = Geographical mile= Mean Sea mile
- 1953: State Waters, Submerged Lands Act extended 3 nautical mile (M)
- 1929: First International Hydrographic Agreement (BIPM): 1 nautical mile (M)= 1,852 m
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