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The key difference between them is the requirement for on-board performance monitoring and alerting. A navigation specification that includes a requirement for on-board navigation performance monitoring and alerting is referred to as an RNP specification. One not having such a requirement is referred to as an RNAV specification.
A simple diagram showing the main difference between traditional navigation and RNAV methods. Area navigation (RNAV, usually pronounced as / ˈ ɑːr n æ v / "ar-nav") is a method of instrument flight rules (IFR) navigation that allows an aircraft to choose any course within a network of navigation beacons, rather than navigate directly to and from the beacons.
The test statistic used is a function of the pseudorange measurement residual (the difference between the expected measurement and the observed measurement) and the amount of redundancy. The test statistic is compared with a threshold value, which is determined based on the requirements for the probability of false alarm (Pfa) and the expected ...
An example of this is the term "P-RNAV" (Precision RNAV) that Europe still uses (2019), which elsewhere is called "RNAV 1". The terms RNAV and RNP was earlier used with little functional difference. RNP required a certain level of performance but made no attempt to define how it was to be guaranteed. The two upper chart strips show the current ...
GNSS-2 is the second generation of systems that independently provide a full civilian satellite navigation system, exemplified by the European Galileo positioning system. [5] These systems will provide the accuracy and integrity monitoring necessary for civil navigation; including aircraft.
A "GNSS compass" uses a pair of antennas separated by about 50 cm to detect the phase difference in the carrier signal from a particular GNSS satellite. [8] Given the positions of the satellite, the position of the antenna, and the phase difference, the orientation of the two antennas can be computed.
The receiver clock is then adjusted so its TOT matches the satellite TOT (which is known by the GPS message). By finding the clock offset, GNSS receivers are a source of time as well as position information. Computing the TOT is a practical difference between GNSSs and earlier TDOA multilateration systems, but is not a fundamental difference.
The use of GNSS in aircraft is becoming increasingly common. GNSS provides very precise aircraft position, altitude, heading and ground speed information. GNSS makes navigation precision once reserved to large RNAV-equipped aircraft available to the GA pilot. Recently, many airports include GNSS instrument approaches.