GPS Global Positioning Systems

GPS devices communicate via a NMEA (National Marine Electronic Association) spec which costs about $250.

See also:

• http://vancouver-webpages.com/peter/nmeafaq.txt (cached 20010105112743)
• http://www.stv5730A.co.uk There are also a couple of PC programs for creating *.sti files for NMEA sentences available for download from the free demo code page
• http://www.schaltungen.de/schaltung/computer/gps-empfang.html circuit for a self built GPS.
• http://www.tech-tools.com/src5.htm by Brian Marbach KE4LWB.  This program takes GPS data, accelerometer, pressure, and temperature data. It uses this information to fire paracutes. Then, it sends it out by 1200 bps AX.25 packet beacon. It also saves the data onboard on 2 16k bit EEproms. The program updates all information once a second based on the timeing pulse out of the Garmin GPS LVC reciever. For remote launching, an NHRC repeater controller was used to give a lauch signal.
• http://spiff.rit.edu/richmond/ritobs/kiwi/kiwi.html Video overlay of GPS precision timestamps

Suppliers:

• Garmon produces a unit with integral antenna and serial NMEA output
• Rockwell, Jupiter - 12 channel aith NMEA serial output
• Trimble SK8
• http://www.sigem.ca VERY affordable. The entire receiver unit (12 sattelites!) costs about $135 in small quantities. The wiring diagram is a builder's dream! Coax connector for antenna is soldered on the board. Then there's a 10 pin header for power and data, and the data is already formatted in NMEA 0183 format.
• http://www.axiomnav.com/

Garmin GPS 16/17 to DB9 PC serial port interconnect:

Here is a Javascript function to calculate distance in miles. Change the multiplier to equal the number of your preferred units in one mile. For example, to get results in feet the multiplier would be 5280.

function calcDist(lon1,lat1,lon2,lat2) {
   var r = 3963.0;
   var multiplier = 1; 
   return multiplier * r * Math.acos(Math.sin(lat1/57.2958) *
           Math.sin(lat2/57.2958) +  Math.cos(lat1/57.2958) *
           Math.cos(lat2/57.2958) * Math.cos(lon2/57.2958 -
           lon1/57.2958));
}:

See:

• /techref/datafile/location.htm Location Data, Physical Address+
• Geocoding Images
• Navigation Methods

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