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Handheld GPS
, 08 26th, 2009
How 
handheld GPS units work
Global Positioning System (GPS) is a navigation technology that provides precise time and location data by using 24 Navigation Satellite Timing and Ranging (NAVSTAR) satellites. Each satellite completes one Earth orbit every 12 hours. They are positioned at an altitude that allows them to cover the same ground once every 24 hours (minus four minutes).
Each satellite carries an atomic clock, transmitting both its position and a time signal, which a GPS receiver picks up. They are positioned so that at least four can be seen from any spot on the Earth. Since a handheld GPS unit can receive data from multiple satellites and each satellite provides information that is appropriate to its own location and distance, the GPS unit performs the mathematics and arrives at a position fix to within 50 to 100 feet. Many factors can have an impact on accuracy, including atmospheric conditions, buildings, tunnels and heavy foliage. However, reviewers say that the latest high-sensitivity GPS receiver chips all but eliminate those issues.
Most GPS units also use Wide Area Augmentation System (WAAS). This system is based on a network of 25 ground-reference stations. Each station receives GPS satellite signals, corrects any errors, and then forwards corrected signals to a Wide Area Master Station, which makes some additional calculations and uploads the newly corrected data to a satellite. The message is finally broadcast on the same GPS frequency and picked up by GPS receivers capable of reading WAAS signals and within the broadcast coverage area of the WAAS. The difference in accuracy can be significant: a WAAS-enabled GPS receiver can fix your position to less than 10 feet. While that might not make a big difference if you’re driving in a car, it’s a big deal if you’re on the ground trying to find the turn to your base camp.
Most handheld GPS units provide the ability to store up to 1,000 or more waypoints , which are simply coordinates for a selected location. You can program waypoints while you’re traveling, or you can program them before you leave home or camp. It’s a fundamental marker that aids the unit in plotting the routes that interest you — sort of a virtual breadcrumb trail.
August 28th, 2009 at 2:19 am
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August 28th, 2009 at 2:20 am
Handheld GPS | Marine Accessories…
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August 28th, 2009 at 2:20 am
Handheld GPS | Marine Accessories…
Only in this site will you be getting the best selection and variety of marine accessories which you may need. In here, it’s all the greatest and the most needed will you ever enjoy shopping….
August 28th, 2009 at 2:21 am
Handheld GPS | Marine Accessories…
Only in this site will you be getting the best selection and variety of marine accessories which you may need. In here, it’s all the greatest and the most needed will you ever enjoy shopping….
August 28th, 2009 at 2:21 am
Handheld GPS | Marine Accessories…
Only in this site will you be getting the best selection and variety of marine accessories which you may need. In here, it’s all the greatest and the most needed will you ever enjoy shopping….