由於IGS 組織對所提供之衛星星曆與鐘差改正精度，已大幅提升，現在之星曆差已小於5 公分、鐘差小於0.1ns，即使是推估精度星曆差亦小於10 公分、鐘差小於5ns，因此對於需高精度星曆之精密單點定位，相當有助益。由於單點定位僅需一部衛星接收儀，即可獲得絕對位置，不若相對定位需同時若干部一起作業，減少工作負擔，而且所獲精度若不輸於相對定位精度，則將來之應用空間更廣。
自2005年九月美國國防部開始部署新一代GPS Block IIR-M型衛星起，至今此類衛星已有6顆在天空運行，對民間使用者而言，它最大之吸引力為增加第二民用碼L2C，它可有效處理有關大氣層對信號產生折射的問題，以及正確解算週波未定值。此項發展，對於需精密定位精度之測量，提供了相當良好的工具。
本研究僅針對L1C與L2C結合解算之可行性，作深入之探討，以及與僅有L1C之解算精度作一比較，驗證雙頻雙碼結合之優越性。 The International GNSS Service (IGS) has been providing the most precise satellite ephemerides and clock collection（ephemeris error ＜5cm, clock error ＜0.1ns）, even the predicted ephemeris and clock data（ephemeris error ＜10cm, clock error ＜5ns） available from IGS in real time are improved dramatically. It has the benefit for increasing the accuracy of precise point positioning (PPP). The success of this technique will provide a more flexible operation for precise positioning.
The new generation GPS satellite Block-IIR-M1 launched at Sept. 26, 2005. Up to now, there are at least 6 operation satellites of Block-IIR-M in the sky. The new era of duel frequencies duel codes is coming. It will improve the accuracy and reliability of satellite positioning dramatically. Since the declaration of Initial Operation Capability (IOC) of GPS in 1993, the anti-spoofing (AS) has come into operation. It makes trouble for precise positioning. For overcome those problems, the special techniques of signal processing were developed, such as, squaring technique. The navigation signals broadcast of the Block-IIR-M satellites will increase the second civilian signal L2C. It is the good news for people who want to improve the reliability of positioning. The new civilian signals include two carrier phase (L1 and L2) and two codes (L1C and L2C). Therefore, a linear combination of both phases and codes observables can be organized. This combination eliminates the effect of the ionosphere, the geometry, the clocks and the troposphere. It is help for rapid positioning.
