Low cost system and method for making dual band gps measurements

Abstract

A low-cost, solid-state position sensor system suitable for making precise code and carrier phase measurements in the L1 and L2 bands of GPS uses an ordinary, low-cost OEM card single-frequency carrier phase tracking C/A code receiver and includes low-cost hardware for sensing the L1 and L2 components of GPS carrier phase. Such measurements are suitable for general use in a variety of fields, including surveying. They are also of sufficient quality to be used in controlling heavy machinery, such as aircraft, farm tractors, and construction and mining equipment. A C/A code continuous tracking GPS receiver is used to produce GPS positioning fixes and real-time L1 carrier phase measurements. This C/A code receiver generates timing and reference information for a digital sampling component. This sampling component processes the L1 and L2 signals from the GPS signals in view. A digital signal processing component coupled to this sampling component processes the raw samples in synchronous, batch form including a step to precisely unwrap the P(Y) carrier phase to baseband. The receiver outputs synchronous, carrier phase measurements associated with each ranging source and signal observable. The synchronous raw carrier phase measurements from the continuous tracking C/A code receiver and the digital sampling component may be used to resolve the cycle ambiguities to each ranging source with respect to a reference station at a known location. Within a short interval typically tens of seconds from initial turn on, continuous, synchronous raw measurements are provided by the GPS receiver and processed into precise position fixes.