2. Data Analysis: Theory2.1 Introdu

2. Data Analysis: Theory
2.1 Introduction to GPS Measurements
High-precision geodetic measurements with GPS are performed using the carrier beat phase, the
output from a single phase-tracking channel of a GPS receiver. It is the difference between the
phase of the carrier wave implicit in the signal received from the satellite, and the phase of a local
oscillator within the receiver. The carrier beat phase can be measured with sufficient precision that
the instrumental resolution is a millimeter or less in equivalent path length. For the highest relativepositioning
accuracies, carrier beat phase observations must be obtained simultaneously at each
epoch from several stations (at least two), for several satellites (at least two), and at both the L1
(1575.42 MHz) and L2 (1227.6 MHz) GPS frequencies. The dominant source of error in a phase
measurement or series of measurements between a single satellite and ground station is the
unpredictable behavior of the time and frequency standards ("clocks") serving as reference for the
transmitter and receiver. Even though the GPS satellites carry atomic frequency standards, the
instability of these standards would still limit positioning to the several meter level were it not for
the possibility of eliminating their effect through signal differencing.
A second type of GPS measurement is the pseudo-range, obtained using the 300-m-wavelength CA
("coarse acquisition") code or 30-m-wavelength P ("protected") code transmitted by the satellites.
Pseudo-ranges provide the primary GPS observation for navigation but are not precise enough to be
used alone in geodetic surveys. However, they are useful for synchronizing receiver clocks,
resolving ambiguities and repairing cycle slips in phase observations, and as an adjunct to phase
observations in estimating satellite orbits.
For a single satellite, differencing the phases (or pseudo-ranges) of signals received simultaneously
at each of two ground stations eliminates the effect of bias or instabilities in the satellite clock. This
measurement is commonly called the between-stations-difference, or single-difference observable.
If the stations are closely spaced, differencing between stations also reduces the effects of
tropospheric and ionospheric refraction on the propagation of the radio signals If the ground
stations have hydrogen-maser oscillators (with stabilities approaching 1 part in 1015 over several
hours), then single differences can, in principle, be useful, as they are for VLBI. In practice,
however, it is seldom cost effective to use hydrogen masers and single difference observations in
GPS surveys. Rather, we form a double difference by differencing the between-station differences
also between satellites to cancel completely the effects of variations in the station clocks. In this
case the observations are just as accurate with low-cost crystal oscillators as with an atomic
frequency standard (though the use of the latter may make editing a bit easier).

結果 (中文) 1:

2.数据分析： 理论2.1 GPS 测量简介用载体拍阶段，进行 gps 高精度大地测量从单个相位跟踪通道 GPS 接收机的输出。之间的区别是它隐含在从卫星上接收到的信号的载波相位和本地的阶段在接收器内的振荡器。载波击败相位可以测量具有足够的精度，仪器的分辨率是一毫米或更小的等价路径长度。为最高 relativepositioning准确性，承运人击败相位观测值必须同时得到在每个从几个地点 （至少两个），几个卫星 （至少两个），并在这两个 L1 的时代(1575.42 MHz) 和 L2 (1227.6 MHz) GPS 频率。在一个阶段错误的主要来源测量或测量单个卫星与地面接收站之间系列不可预知的行为，作为参考时间和频率的标准 ("时钟")发射机和接收机。尽管 GPS 卫星携带原子频率标准这些标准的不稳定性将仍然限制定位到几米一级不消除他们通过信号差分法的作用的可能性。GPS 测量的二种类型是伪距，获得使用 300-m-波长 CA（"粗习得"） 代码或 30-m-波长 P （"受保护"） 通过卫星传送的代码。伪范围提供初级的 GPS 观测用于导航，但并非不够明确，因此在大地测量中单独使用。然而，它们被用于同步接收机时钟解决含糊不清和修理周期滑相位观测值，以及辅助阶段在估计的观测卫星的轨道。一颗卫星，差分法同时接收到的信号的阶段 （或伪范围）在每两个地面站就消除了偏见或卫星时钟中的不稳定性的影响。这测量通常称为之间站-差分或单差观测。如果站相距甚近，差分站之间也减少的影响对流层和电离层折射对传播的无线电信号如果地面驻地有氢微波激射器振荡器 （与稳定性接近 1 部分 1015 年数小时），然后单差异，原则上，可能有用，因为它们是为 VLBI。在实践中，然而，很少成本有效地使用氢脉泽和单一的不同意见Gps 观测结果。相反，我们形成双差差分站之间的差异此外之间卫星完全取消驻地时钟的变化的影响。在这案例的意见是与低成本晶体振荡器随着原子一样精确频率标准 （尽管后者的使用可能会使编辑有点更容易）。

結果 (中文) 3:

2。数据分析：2.1介绍GPS测量理论

高精度大地测量GPS是利用载波相位进行相位跟踪，从一个单一的GPS接收机信道
输出。它是从卫星接收到的载波信号中的隐含
相位之间的差异，和相位的本地振荡器在接收机
。的载波相位可以以足够的精度测量，仪器的分辨率是
毫米或等效路径长度小于。对于最高relativepositioning
载波相位观测值的精度，必须同时获得在每个
时代几个站（至少两个），多颗卫星（至少两个），和在两L1
（1575.42兆赫）和L2（1227。GPS频率6兆赫）。在一个阶段
测量或一个单一的卫星和地面站之间的系列测量误差的主要来源是
不可预知的行为的时间和频率标准（“时钟”）为
发射机和接收机参考。虽然GPS卫星携带的原子频率标准，其
这些标准的不稳定性仍然限制定位到几米的水平不是通过信号差分
消除其影响的可能性。
第二类GPS伪距测量，获得使用300-m-wavelength CA
（“粗捕获”）代码或30-m-wavelength P（“保护”）的卫星
传输代码。伪范围提供导航主要GPS观测但不够精确是
单独使用的大地测量。然而，它们可用于同步接收机时钟，解决歧义和
相位观测值的周跳修复，并在估计卫星轨道观测相
辅助
为一个单一的卫星，差分相位（或伪范围）的信号同时接收
在每两个地面站，消除了在卫星钟差或不稳定性的影响。这是通常被称为
测量站之间的差异，或单差观测。
如果站站之间的紧密间隔的，差也减少
的影响对流层和电离层如果地面
站氢脉泽振荡器的无线电信号传播的折射（稳定的接近1的一部分在1015小时，然后在几个
）单差异，原则上，是有用的，因为它们是VLBI。在实践中，但它很少
，成本有效的使用在
氢脉泽和单差观测值GPS调查。相反，我们形成一个双差分的差分之间的差异也站
卫星之间取消完全在钟变化的影响。在这情况下，观测
一样精确的低成本晶体振荡器作为频率标准原子
（虽然后者的使用可以使编辑更容易一点）。