User`s guide

Appendix
Motorola GPS Products - M12+ User's Guide Revision 6.X 09FEB05
199
Binary Pulse Code Modulation
Pulse modulation using a string of binary numbers (codes). This coding is usually
represented by ones and zeros with definite meanings assigned to them, such as
changes in phase or direction of a wave.
Bluebook
A slang term derived from a blue NGS reference book. The book contains information
and formats required by NGS for survey data that is submitted to be considered for use in
the national network.
C/A Code
The Coarse/Acquisition (or Clear/Acquisition) code modulated onto the GPS L1 signal.
This code is a sequence of 1023 pseudorandom binary bi-phase modulations on the GPS
carrier at a chipping rate of 1.023 MHz, thus having a code repetition period of one
millisecond. This code was selected to provide good acquisition properties.
Carrier
A radio wave having at least one characteristic (such as frequency, amplitude, phase)
that may be varied from a known reference value by modulation.
Carrier Beat Phase
The phase of the signal that remains when the incoming Doppler-shifted satellite carrier
signal is beat (the difference frequency signal is generated) with the nominally constant
reference frequency generated in the receiver.
Carrier Frequency
The frequency of the unmodulated fundamental output of a radio transmitter. The GPS L1
carrier frequency is 1575.42 MHz.
Celestial Equator
The great circle that is the projection of the earth's geographical equator of rotation onto
the celestial sphere. Its poles are the north and south celestial poles.
Celestial Meridian
The vertical great circle on the celestial sphere that passes through the celestial poles,
the astronomical zenith, and the nadir.
Chip
The length of time required to transmit either a one or a zero in binary pulse code. One
chip of the C/A code is about 977 ns long, which corresponds to a distance of 293m.
Chip Rate
Number of chips per second (e.g., the C/A code chip rate = 1.023 MHz).
Clock Offset
Constant difference in time readings between two clocks.