User`s guide

Appendix
Motorola GPS Products - M12+ User's Guide Revision 6.X 09FEB05
206
Mean Anomaly
M = n(t - T), where n is the mean motion, t is the time, and T is the instant of perigee
passage.
Mean Motion
n = 2/P, where P is the period of revolution.
Microstrip Antenna
A two-dimensional, flat, precisely-cut piece of metal foil glued to a substrate.
Monitor Station
Any of a worldwide group of stations used in the GPS control segment to monitor satellite
clock and orbital parameters. Data collected at these sites are linked to a master station
where corrections are calculated and controlled. These data are uploaded to each
satellite at least once per day from an uplink station.
Multichannel Receiver
A receiver containing many independent channels. Such a receiver offers the highest
signal-to-noise ratio (SNR) because each channel tracks one satellite continuously.
Multipath
Interference similar to ghosts on a television screen, which occurs when multiple signals
arrive at an antenna after having traversed different paths. In GPS, the signal traversing
the longer path will yield a larger pseudorange estimate and increase the error. Multiple
paths may arise from reflections from structures near the antenna or the ground.
Multipath Error
A positioning error resulting from interference between radio waves that have traveled
between the transmitter and the receiver by paths of different electrical lengths.
Multiplexing Channel
A receiver channel that is sequenced through several satellite channels (each from a
specific satellite and at a specific frequency) at a rate which is synchronous with the
satellite message bit rate (50 bits per second, or 20 milliseconds per bit). Thus, one
complete sequence is completed in a multiple of 20 milliseconds.
NAD-83
North American Datum, 1983
NAVDATA
The 1500-bit navigation message broadcast by each satellite at 50 bps on both the L1
and L2 signals. The message contains system time, clock correction parameters,
ionospheric delay model parameters, and the satellite's ephemeris and health. This
information is used by the GPS receiver in processing GPS signals to obtain user
position, velocity, and time.