Geodetic Data Collection Techniques - Geodesy: Introduction to Geodetic Datum and Geodetic Systems - page 42

3. Display the positioning results. As soon as the receiver locks onto four (or more
than four) satellites, it will begin the positioning and display the results. Position
and velocity are generally displayed. The receiver constantly updates position-
ing and velocity results based on the selected data update rate.
Phase Measurement Receiver
Since the carrier wave is much shorter in wavelength than the pseudo-random code,
in the case of the same resolution the observation accuracy of the carrier phase is
much higher than that of the code phase. For example, the wavelength of the carrier
L 1 is 19 cm, so the error of the corresponding distance observations is about 2 mm,
whereas for the carrier L 2 the corresponding error is about 2.3 mm. The carrier
phase measurement is the most accurate method nowadays and many companies
have produced GPS phase measurement receivers of different types. The
MacrometerV-1000 produced by the American company Litton Aero Service is a
single frequency (L 1 ) phase measurement receiver and is the earliest manufactured
for commercial use.
2.3.2 Satellite Laser Ranging
Satellite Laser Ranging (SLR), rising in the mid-1960s, is a new space geodetic
technique that determines the distance between laser station and a satellite using the
laser ranger to trace and observe the satellites installed with laser reflectors. To
begin with, SLR employed the BE-C satellite. Then, in 1976 NASA launched a
laser geodynamic satellite LAGEOS-1; in 1992 America cooperated with Italy and
launched the satellite LAGEOS-2 to expand the observation range of SLR on the
Earth. Meanwhile, France, the former Soviet Union, Japan, and Germany succes-
sively launched their SLR satellites. During its development over more than
40 years, the SLR system has improved from 1 m to the present 1 cm in distance
accuracy. It is now one of the main technical means of precise satellite positioning
as well as the most precise among the current various space observation technol-
ogies in terms of data sampling rate and absolute positioning. It not only plays a
decisive role in establishing and maintaining the Global Geocentric Coordinate
System (GGCS) but has also led to great achievements in the field surveying of
modern plate motion, improvements in the Earth gravity model and geocentric
gravitational constant, and the accurate measurement of Earth's rotation parameters
(ERP), etc. (see e.g., Ye and Huang 2000).