Global Positioning System (GPS)    

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What is GPS?

GPS (Global Positioning System) is a satellite-based navigation system. First it was developed by the U.S. Department of Defence to provide a method of simplifying navigation.
Originally designed for military applications, it also provides commercial and recreational users with 24-hour, worldwide navigation coverage with accuracy to 15 meters (49 feet).

How Does GPS Work?

GPS navigation uses satellite ranging to determine your position in relation to a set of satellites orbiting the earth. The GPS constellation is made up of 24 satellites, which continuosly send radio signals containing precise position and time information for each satellite back to earth.
By knowing the position of any 3 or 4 of these satellites and calculating various time differences between the transmitted signals, your GPS receiver can determine its present position anywhere on earth. And once you're under way, your GPS continuously updates your position and provides speed and track information.

Once the receiver is locked onto a set of signals, it can determine how far away each Satellite is by measuring the time it takes to receive each signal. By knowing the distance and position of 3 or more satellites, the GPS receiver can then calculate your position by using a technique called satellite ranging. This calculation, or triangulation, simply measures your position in reference to a set of known objects (the GPS satellites).

Some GPS Positions (central places)
Place Latitude Longitude
San Francisco N 37 48,000' W 122 24,000'
Garmin (Kansas) N 38 57,003' W 94 44,767'
Sydney (Australia) S 34 00,000' E 151 12,000'
Vienna (Austria) N 48 11,858' E 16 20,294'
Amstetten (120 km west of Vienna) N 48 07,000' E 14 52,000'
My Home (Amstetten) N 48 07,478' E 14 52,740'

Distance calculation

Formulas:
  g = acos[sin(ns1) * sin(ns2) + cos(ns1) * cos(ns2) * cos(ew2 - ew1)]
Radius R = 6371 km
Distance dist = 2 * ¶ * R * g / 360
Angle deg = asin[cos(ns2) * sin(ew2 - ew1) / sin g]

Input:
Source ns1, ew1 means degrees north-south and east-west (i.e.: 48,12463 / 14,87900)
Destination ns2, ew2 is the same type as the source

Important:
ns1, ns2 If ns1 or ns2 is north input it positive, if south then negative
ew1, ew2 If ew1 or ew2 is west input it positive, if east then negative

Some distances
Longitude (Meridians) Latitude (only N 47, Austria)
1 111 km (60,0 nmi) 1 75 km
10' 18,5 km (10,0 nmi) 10' 12,5 km
1' 1,85 km (1,0 nmi) 1' 1,25 km
0,1' 185 m (0,1 nmi) 0,1' 125 m
0,01' 18,5 m (0,01 nmi) 0,01' 12,5 m
0,001' 1,85 m (0,001 nmi) 0,001' 1,25 m

nmi = nautical mile (1,85 km)

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