The GPS System is composed of:

• Satellites
• Earth Monitoring Stations
• GPS Receivers

What Is a GPS Satellite?

There are currently 24 satellites orbiting the earth in 6 distinct trajectories. Each satellite completes two orbits around the earth each day, traveling at a speed of about 7,000 MPH. At the highest point in their orbit they are more than 12,000 miles above the earth. From this height, the satellite signals can be received over a large percentage of the surface of the earth. A GPS unit works by receiving multiple satellite signals and calculating the receiver’s position based on triangulation of the different signals. Accuracy is increased with each additional satellite signal that is received so the orbits of the satellites are set so that at most points on the earth there are at least 4 signals that can be received. Of course, this is in theory only since the landscape around you can block some or all of the GPS signals.

What Is a GPS Earth Monitoring Station?

There are four unmanned monitoring stations in the US and one manned master station which is located in Colorado Springs, Colorado. The four unmanned stations relay position data from the satellites to the master station. The master station uses the relayed information to correct the position of the sat tiles and sends the corrected information back to the satellites. This synchronizes the data that each satellite transmits to your GPS receiver and ensures that your receiver is always working with accurate information.

What Is a GPS Receiver?

GPS satellites transmit low power radio signals that can only be picked up if your GPS unit has a direct “line of sight” to the satellite. The signals can penetrate things like glass, plastic and clouds but not solid structures like buildings or rocks. A GPS unit works by triangulating your location based on the position of at least three satellites in the GPS system. It compares the time it takes to receive a signal from each of the satellites in range and calculates your location based on the data.

If you are only able to pick up three satellite signals, your GPS unit can report your location in latitude and longitude. However, when the GPS unit picks up signals from at least four satellites it also calculates your altitude. Now it can report your trip distance, distance to a destination, travel speed and even your altitude if your GPS receiver features an altimeter.

How accurate a GPS unit is depends on its ability to find and lock onto a satellite’s signal. As you might expect, you get what you pay for and the more expensive GPS units are generally more accurate. The best consumer units claim accuracy to within a few feet while the older or less expensive units can be off up to 30-40 feet or more. Where you plan to use your GPS receiver could determine if it’s worth shelling out the extra money for increased accuracy. If you’re using your GPS unit in flatter terrain with a good open view of the sky a less expensive unit could perform nearly as well as the top of the line receiver. However, if you plan to use your receiver in dense tree cover, while hiking in ravines or narrow valleys, or among tall buildings you’ll gain much better accuracy with a more higher end GPS unit.

Now you know the basics about how GPS works and can answer the question “What is GPS?”.

Garmin GPSMap 76 Handheld GPS Navigator
List Price: $251.81
Price: $193.7

Detailed mapping in a completely portable handheld unit! These handheld marvels take the best features from the GPS 76, including its enhanced, high-resolution screen for improved legibility, and gives them full mapping capability. Several navigation pages clearly show your position on a moving map along with important information such as position, speed, heading, distance and more. The units are preloaded with a database of worldwide cities, navaids, tide data for the US, celestial navigation data and a hunting/fishing calendar. They also boast an internal memory capacity of 8MB for uploading mapping data from optional MapSource CD-ROMs, including BlueChart® marine nautical charts and Recreational Lakes with Fishing Hot Spots. With optional MapSource® CDs, you can get highly-detailed maps of highways, city streets, restaurants and hotels or buoys, navaids, wrecks and suggested fishing spots for selected lakes. The built-in quad helix antenna offers superior reception, precise GPS positioning using WAAS technology and accepts an external antenna. You can store up to 1000 waypoints with 50 reversible routes and use the TracBack mode to retrace your path. Display Type: Monochrome Screen Size: 1.6″W x 2.2″H Screen Resolution: 180 x 240 Display Mode: Satellite status, map, highway, compass, active routes Cartography: BlueChart, Topo and more Antenna: Internal quad-helix with MCX external antenna connection Battery Type: Two AA batteries (sold separately) 

Ram Mount Ram Holder For Garmin Dakota 10 And 20
Price: $10.19
This RAM high strength composite cradle is designed to hold the following devices: Garmin Dakota 10 Garmin Dakota 20. Material: High Strength Composite

Lowrance Endura Safari
List Price: $500.49
Price: $384.99
2.7 color touchscreen optimized for outdoor use combined with physical buttons advanced basemap with detailed hillshade primary & secondary roads & key pois directly accepts gpx trails & pois from web communities or other sources plug-&-play & downloadable mapping options such as fishing hot spots multimedia mp3/voice notes picture & video players trip computer records trails altitudes trip times speed & distance traveled power standby mode saves battery life while allowing ultra-fast startup fully turn-by-turn navigation capable for car motorcycle cycling etc. (with optional purchase)

Scott Roy, Product Marketing Manager with Navico, is interviewed with Rural Life TV and Radio to introduce the new Lowrance Endura GPS handheld series. This new handheld GPS series of products includes brilliant touch-screens and packed full of the best topographic mapping data.

Garmin Oregon 200
List Price: $509.86
Price: $390.24
Oregon 200 the newest member of the premium handheld line. this rugged unit with a high-sensitivity gps receiver offers innovative features such as a sunlight readable touchscreen for easy operation as well as the ability to exchange waypoints tracks routes and geocaches wirelessly between units. in addition you can customize your oregon with five different user profiles: automotive marine recreation fitness or geocache. the microsd card makes it simple to load optional maps for different types of adventures. the oregon s detailed mapping and high-resolution color display enhance any outdoor adventure whether on land or water. includes usb cable lanyard owner s manual on disk quick start guide

iPhone 4 and VoxTrek Navigation GPS with offline search and offline routing!

The GPSMAP 60CSx is an upgrade of the GPSMAP 60CS, one of the best selling handheld GPS units for outdoor and marine use. This unit features a removable microSD card so you can expand the mapping memory. This has been one of the most requested features by Garmin customers and is reason enough to upgrade from the GPSMAP 60CS. The microSD card slot is located inside the waterproof battery compartment and users can load map data and transfer routes and waypoints through the unit’s fast USB connection.

Perhaps the most exciting feature of the GPSMAP 60CSx is the new, highly sensitive, third-generation GPS receiver chip by SiRF. This SiRFStar III chip locks on to satellite signals faster and lets users track their position in more challenging conditions like heavy tree cover or deep canyons. The GPSMAP 60CSx also features a barometric altimeter for accurate elevation data and an electronic compass that can be used while stationary.

The GPSMAP 60CSx sports a large color TFT screen and turn-by-turn routing. Each unit ships with a blank 64 MB microSD card. It is possible to purchase new microSD cards that are pre-loaded with MapSource Topo and inland lake maps, BlueChart marine cartography, and City Navigator street maps. You can also take advantage of the removable microSD memory and upload map data to a blank card from your PC. The contains maps of all of the USA on one CD for not much more than just one section of the country on a preloaded microSD card.

Garmin GPSMAP 60CSx Portable Navigator – 2.66 Active Matrix TFT – 12
Price: $380.18
The gpsmap 60csx portable navigator is one of most popular models for outdoor and marine use.  It contains a removable microsd card for detailed mapping memory and a waterproof rugged housing. The microsd card slot is located inside the waterproof battery compartment. It features a new highly sensitive gps receiver that acquires satellites faster and lets users track their location in challenging conditions such as heavy foliage or deep canyons. Owners of new x-series handhelds can also purchase new microsd cards that are pre-loaded with mapsource topo and inland lake maps, bluechart marine cartography, and city navigator street maps.