The Global Positioning System (GPS) is the only fully functional Global Navigation Satellite System (GNSS). The GPS uses a constellation of between 24 and 32 Medium Earth Orbit satellites that transmit precise microwave signals, that enable GPS receivers to determine their location, speed, direction, and time. GPS was developed by the United States Department of Defense. Its official name is NAVSTAR-GPS. Although NAVSTAR-GPS is not an acronym[1], a few backronyms have been created for it[2]. The GPS satellite constellation is managed by the United States Air Force 50th Space Wing.

Similar satellite navigation systems include the Russian GLONASS (incomplete as of 2008), the upcoming European Galileo positioning system, the proposed COMPASS navigation system of China, and IRNSS of India.

Garmin Oregon 300 3” Touchscreen Handheld GPS Unit with a Built-in Basemap and Shaded Relief
Availability: Usually ships in 1 to 2 months
Ships from and sold by Amazon.com
2 new or used available from $492.95
Average customer review:
Oregon 300 features a preloaded worldwide basemap with shaded relief for incredibly detailed map presentation on the unit. The [...]

Garmin Oregon 200 3” Touchscreen Handheld GPS Unit with a Built-in Basemap
Availability: Usually ships in 1-2 business days
Ships from and sold by GizmosForLife
8 new or used available from $383.88
Get in touch with the great outdoors with the Garmin® Oregon 200 handheld GPS unit. This next-generation handheld features a rugged, touchscreen along with a built-in [...]

Garmin Oregon 400T 3” Touchscreen Handheld GPS Unit with Preloaded Topographic Maps
Availability: Usually ships in 1-2 business days
Ships from and sold by GizmosForLife
4 new or used available from $529.95
Oregon 400i Pre-loaded U.S. inland lake and navigable river maps provide boaters and anglers with shoreline details depth contours boat ramps and mile markers for thousand [...]

Garmin Oregon 400C 3” Touchscreen Handheld GPS Unit with BlueChart g2 Coastal Charts
Availability: Usually ships in 1-2 business days
Ships from and sold by 7GIFTS
6 new or used available from $547.99
The Garmin® Oregon 400t handheld GPS unit leads the way with a tough, 3-inch diagonal, sunlight-readable, color, touchscreen display. Its easy-to-use interface means you’ll spend [...]

Garmin Oregon 400i 3” Touchscreen Handheld GPS Unit with U.S. Inland Lakes and a Worldwide Basemap
Availability: Usually ships in 1 to 2 months
Ships from and sold by Amazon.com
2 new or used available from $589.99
Oregon 400C comes with preloaded detailed BlueChart g2 coverage for the coastal U.S. and the Bahamas. The newest member of the [...]