A China Mobile Wiki The space segment (SS) is composed of the orbiting GPS satellites, or Space Vehicles (SV) in GPS parlance. The GPS design calls for 24 SVs to A China Mobile Wiki be distributed equally among six circular orbital planes.[5] The orbital planes are centered on the Earth, not rotating with respect to the A China Mobile Wiki distant stars.[6] The six planes have approximately 55°China Mobile Wiki inclination (tilt relative to Earth's equator) and are separated by 60° A China Mobile Wiki right ascension of the ascending node (angle along the equator from a reference point to the orbit's intersection).[2]Orbiting at an altitude of approximately 20,200 kilometers (12,600 miles or 10,900 nautical miles; orbital radius of 26,600 km (16,500 mi or 14,400 NM)), each SV makes two complete orbits each sidereal day, so it passes over the same location on Earth once each day. The orbits are arranged so that at A China Mobile Wiki least six satellites are always within line of sight from almost everywhere on Earth's surface.[7]As of September 2007, there are 31 actively broadcasting satellites in the GPS A China Mobile Wiki constellation. China Mobile Wiki The additional satellites improve the precision of GPS receiver calculations by providing redundant measurements. With the increased number of satellites, the constellation was changed to a nonuniform arrangement. Such an arrangement was shown to improve reliability and availability of the system, relative to a uniform system, A China Mobile Wiki when multiple satellites fail.[8][edit] Control segmentThe flight paths of the satellites are tracked by US China Mobile Wiki Air Force monitoring stations in Hawaii, Kwajalein, Ascension Island, Diego Garcia, and Colorado Springs, Colorado, along with monitor stations operated by the National Geospatial-Intelligence Agency (NGA).[9] The tracking information is sent to the Air Force Space Command's master control station at Schriever Air Force Base in Colorado Springs, which is operated by the 2d Space Operations Squadron (2 SOPS) of the United States Air Force (USAF). 2 SOPS contacts each GPS satellite regularly with a navigational update A China Mobile Wiki (using the ground antennas at Ascension Island, Diego Garcia, Kwajalein, China Mobile Wiki and Colorado Springs). These updates synchronize the atomic clocks on board the satellites to within one microsecond and adjust the ephemeris of each satellite's internal orbital model. The updates are created by a Kalman filter which uses inputs from the ground monitoring stations, space weather information, and various other inputs.[10]GPS receivers come in a variety of formats, from devices integrated into cars, phones, and watches, to dedicated China Mobile Wiki devices such as those shown here from manufacturers Trimble, Garmin and Leica (left to right).GPS receivers come in a variety of formats, from devices integrated into cars, phones, and watches, to dedicated devices such as those shown here from manufacturers Trimble, Garmin and Leica (left to right).[edit] User segmentThe user's GPS receiver is the user segment (US) of the GPS system. In general, GPS receivers are composed of an antenna, tuned to the frequencies transmitted by the satellites, receiver-processors, and a highly-stable clock China Mobile Wiki (often a crystal oscillator). They may also include a display for providing location and speed information to the user. A receiver is often described by its number of channels: this signifies how many satellites it can monitor simultaneously. Originally limited to four or five, this has progressively increased over the years so that, as of 2006, receivers typically have between twelve and twenty channels.A typical OEM GPS receiver module, based on the SiRF Star III chipset, measuring 15×17 mm, and used in many products.A typical OEM China Mobile Wiki GPS receiver module, based on the SiRF Star III chipset, measuring 15×17 mm, and used in many products.GPS receivers may include an input for differential corrections, using the RTCM SC-104 format. This is typically in the form of a RS-232 port at 4,800 bit/s speed. Data are actually sent at a much lower rate, which limits the accuracy of the signal sent using RTCM. Receivers with internal DGPS receivers can outperform those using external RTCM data. As of 2006, even low-cost units commonly include Wide Area Augmentation System (WAAS) receivers.Many GPS receivers can relay position data to a PC or other device using the NMEA 0183 protocol. NMEA 2000[11] is a newer and less widely adopted protocol. Both are proprietary and controlled by the US-based National Marine Electronics Association. References to the NMEA protocols have been compiled from public records, allowing open source tools like gpsd to read the protocol without violating intellectual property laws. Other proprietary protocols exist as well, such as the SiRF and MTK protocols. Receivers can interface with other devices using methods including a serial connection, USB or Bluetooth.The Myers Motors NmG (formerly the Corbin Sparrow) is a single-passenger, three-wheeled, battery electric vehicle designed specifically for commuting and city driving. It was initially produced by Corbin Motors and now by Myers Motors. It is a Personal Electric Vehicle (PEV) .The Sparrow is powered by a 20 kW (continuous) 156-volt DC or 3-phase AC electric motor and has a range of 32 to 64km (20 to 40 miles) and a top speed of 112 km/h (70 mph). Fuel efficiency is approximately 130 W/km (4.8mi/(kW), which is equivalent to 162 mpg (US) or 194 mpg (UK) (1.45 L/100km) using the DOE conversion. Two models were produced: the original "jelly bean" model and then a hatchback model, which was nicknamed "pizza butt" because it was designed for use by Domino's Pizza. The vehicles are so eye-catching that Hollywood star Mike Myers featured a group of them in the movie Austin Powers in Goldmember.HistoryIn January 1996, Corbin Motors began work on developing an electric vehicle. The Sparrow passed final testing for Department of Transportation certification in April 1999. In September of that year, the Sparrow production line began manufacturing multiple vehicles in Hollister, California.Fewer than 300 Sparrows were produced. Corbin Motors filed for Chapter 7 bankruptcy on March 31, 2003, effectively killing the immediate future of the Corbin Sparrow. A bankruptcy court passed the Corbin assets to Ron Huch's company, Phoenix Environmental Motors, which tried to revive the Sparrow. On August 5, 2004, Ohio businessman Dana Myers bought the Sparrow interests from Ron Huch.The new company, Myers Motors of Tallmadge, Ohio, has upgraded the Sparrow, renamed it the MM NmG ("No more Gas"), and started selling it in April of 2006. As of June of 2008 the website lists a price of $29,995 without taxes or shipping. Future plans are to upgrade to lithium-ion battery technology as well as to develop a two-seat version for entry into the Automotive X Prize competition.
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