Z-Count
The fundamental GPS time unit. It is a 29-bit binary number, of which the 10 most significant bits give the binary representation of the GPS week number, and the 19 least significant bits give the time-of-week (TOW) count in units of 1.5 seconds. A truncated version of the TOW with 6-second epochs is included in the navigation message hand-over word. Zenith
The point on the celestial sphere that is directly above the observer. Zenith telescope
A telescope for observing stars near the zenith. Zero Baseline
A Zero Baseline test can be used to study the precision of receiver measurements as well as the data processing software. The experimental setup involves connecting two GPS receivers to the same antenna. When two receivers share the same antenna, biases such as those which are satellite (clock and ephemeris) and atmospheric path (troposphere and ionosphere) dependent, as well as errors such as multipath cancel during data processing. The quality of the resulting “zero baseline” is therefore a function of random observation error (or noise), and the propagation of any receiver biases that do not cancel in double-differencing. |
