Search results
Results from the WOW.Com Content Network
Vehicle navigation on a personal navigation assistant Garmin eTrex10 edition handheld. A satellite navigation device or satnav device, also known as a satellite navigation receiver or satnav receiver or simply a GPS device, is a user equipment that uses satellites of the Global Positioning System (GPS) or similar global navigation satellite systems (GNSS).
The GPS OCX program represents a critical part of GPS modernization and provides information assurance improvements over the current GPS OCS program. OCX will have the ability to control and manage GPS legacy satellites as well as the next generation of GPS III satellites, while enabling the full array of military signals.
The United States' Global Positioning System (GPS) consists of up to 32 medium Earth orbit satellites in six different orbital planes. The exact number of satellites varies as older satellites are retired and replaced. Operational since 1978 and globally available since 1994, GPS is the world's most utilized satellite navigation system.
The GPS system space segment is composed of 24 to 32 satellites in medium Earth orbit at an altitude of approximately 20,200 km (12,600 mi). The satellites are in six specific orbits and transmit highly accurate time and satellite location information which can be used to derive distances and calculate position.
GPS encodes this information into the navigation message and modulates it onto both the C/A and P(Y) ranging codes at 50 bit/s. The navigation message format described in this section is called LNAV data (for legacy navigation). The navigation message conveys information of three types: The GPS date and time, and the satellite's status.
In the field of geodesy, Receiver Independent Exchange Format (RINEX) is a data interchange format for raw satellite navigation system data. This allows the user to post-process the received data to produce a more accurate result — usually with other data unknown to the original receiver, such as better models of the atmospheric conditions at time of measurement.
The TTFF is commonly broken down into three more specific scenarios, as defined in the GPS equipment guide: Cold or factory The receiver is missing or has inaccurate estimates of its position, velocity, the time, or the visibility of any of the GPS satellites. As such, the receiver must systematically search for all possible satellites.
GPS Landing and Navigation System GLNU GPS Landing and Navigation Unit GLS GBAS Landing System GLU GPS landing unit GM guidance material GMM general maintenance manual GMT Greenwich Mean Time: GND ground: Airfield operations GP glide path See instrument landing system: GPP general practices and procedures GPS Global Positioning System: Avionics GPU