gps

device gps pda
gps hiking review
portable gps
gps unit for sale
lowrance gps fish finder
garmin gpsmap 60cs gps receiver
discount gps navigation portable system
cobra gps
treo 600 gps software
magellan gps 300 manual
360 blue dock gps receiver tooth
download garmin gps map
garmin gps auto
best gps unit
gps pda handheld pcs
20 gps software
gps software
gps solution tracking vehicle
garmin gps blue tooth
best pda gps software
device gps gps recreational
330 gps magellan map
magellan gps receiver
coordinate gps map
gps product
gps mobile navigation system
gps oem receiver
gps for laptop pc
garman gps
gilsson gps antenna
gps laptop tracking
gps aerial map
magellan sportrak map gps
gps topographic map
gps tracking of laptop
trimble gps receiver
aviation gps pda software
60cs garmin gps map
cingular cell phone gps tracking
ram gps mount
blue tooth gps receiver
cheap portable gps
gps pda accessory
gps system tracking uk vehicle
pc pocket gps navigation
gps map pda
gps navigation review system
gps antenna mount
emerson gps touch screen navigation system
cnet gps review
car stereo with gps
garmin gps for laptop computer
gps it site tracking
gps tracking software
gps greece map
gps navigation dvd
3600 garmin gps ique receiver
tom tom gps system
gps vehicle tracking
auto gps rating
motorcycle gps review
pda gps adapter
gps car antenna
data gps tracking vehicle
garmin aviation gps
gps navigation portable system
gps cell phone cingular
europe gps software
gps for ipaq review
holux gps receiver
gps rider tom tom
gps locator for kid
antenna gps receiver
fishing gps map
discount lowrance gps
gps software laptop
garmin gps 72
magellan explorist 100 gps
gps mobile locator
tom tom gps map
golf gps pda
computer gps laptop navigation
pocket pc gps navigation software
computer gps reciever
best device gps
garmin gps i2 streetpilot

The GPS or Global Positioning System is a global navigation system used for military and civilian applications alike.

As a positioning system, GPS allows users to map waypoints, tracking their position on a map to within a few meters of their exact location. Civilian use GPS systems are made by companies such as Magellan, Garmin and Trimble.

One of biggest problems for GPS accuracy is that changing atmospheric conditions change the speed of the GPS signals unpredictably as they pass through the ionosphere. The effect is minimized when the satellite is directly overhead and becomes greater toward the horizon, as the satellite signals must travel through the greater "thickness" of the ionosphere as the angle increases. Once the receiver's rough location is known, an internal mathematical model can be used to estimate and correct for the error.

In late 2005, the US government introduced the first in a series of new generation GPS staellites offering new capabilities. Chief among these is a second civilian GPS signal called L2C for greater accuracy and reliability.

The GPS system uses a satellite constellation of 24 satellites in intermediate circular orbits. The orbits are designed so at least four satellites are always within line of sight from almost any place on earth. The constellation also includes three spare satellites in orbit.

The first experimental Block-I GPS satellite was launched in February 1978. The GPS satellites were initially manufactured by Rockwell International and now manufactured by Lockheed Martin.

GPS is coming into common use in cars these days. Most new cars allow you to purchase GPS technology that will help you plot your trip from one location to the next.

In 1996, President Bill Clinton issued a policy directive declaring GPS to be a dual-use system, meaning that it could be made avilable for a wide range of civilian and military purposes.

Selective Availablity typically added signal errors of up to about 10 m horizontally and 30 m vertically. The inaccuracy of the civilian signal was deliberately encoded so as not to change very quickly, for instance the entire eastern US area might read 30 m off, but 30 m off everywhere and in the same direction. In order to improve the usefulness of GPS for civilian navigation, Differential GPS was used by many civilian GPS receivers to greatly improve accuracy.

When it was first deployed, GPS included a feature called Selective Availability (or SA) that introduced intentional errors of up to a hundred meters into the publicly available navigation signals, making it difficult to use for guiding long range missiles to precise targets. Additional accuracy was available in the signal, but in an encrypted form that was only available to the United States military, its allies and a few others, mostly government users.

In early years, the US military made the civilian application purposefully less powerful than it could. But since August 2000, the GPS civilian application provides the accuracy of GPS signals to within 2 meters (6 ft). Fact is, GPS accuracy can be improved further, to about 1 cm (half an inch) over short distances, using techniques such as Differential GPS (DGPS).

During the Gulf War, the shortage of military GPS units and the wide availability of civilian ones among personnel resulted in disabling the Selective Availability. In the 1990s the FAA started pressuring the military to turn off SA permanently. This would save the FAA millions of dollars every year in maintenance of their own, less accurate, radio navigation systems. The military resisted for most of the 1990s, but SA was eventually turned off in 2000 following an announcement by then US President Bill Clinton, allowing all users to enjoy nearly the same level of access.

GPS has become a vital global utility, indispensable for modern navigation on land, sea, and air around the world, as well as an important tool for map-making, and land surveying. GPS also provides an extremely precise time reference, required for telecommunications and some scientific research, including the study of earthquakes.

The US military has developed the ability to locally deny GPS (and other navigation services) to hostile forces in a specific area of crisis without affecting the rest of the world or its own military systems. Such Navigation Warfare uses techniques such as local jamming to replace the blunt, world-wide degradation of civilian GPS service that SA represented.

More accurate GPS receivers are used these days in surveying to accurately locate boundaries, structures and so on.

The author would have loved to have used GPS years ago in college. We had a class where we used maps and compasses. We were given precise coordinates and had to plot a course through woods and streams and swamps to find and sign in at specific latitude and longitude coordinates. Today, this sport, now called "geocaching", is a popular activity, particularly for outdoor hiking enthusiasts.

Hand-held GPS units are often used by hikers and mountain climbers to plot their courses and to accurately reflect exactly where they are. The author once used GPS to organize a helicopter evacuation of an injured motorcycle rider in a remote region of the La Sal mountains in Utah. A reading was taken, coordinates given, and the pilot was able to find us with ease.

garmin gps i2 streetpilot online resources.
Site map