摘要:
A method for obtaining integer ambiguity solutions based on externally provided constraints, e.g., altitude. Such constraints are useful in reducing the computational burden created by the search problem, and using constraints is particularly more effective when a more limited number of satellite vehicles are visible than is ordinarily the case. The constraints are exercised in a search algorithm. As the branches of the integer ambiguity search tree are traversed, an additional test is used to determine if the current search candidate is compatible with such external constraint. Because a three-dimensional position is associated with each search candidate, the branch clipping is straightforward. The ambiguity candidates are each only acceptable if their locations in space are within a confidence region bound set determined from the external constraint. Any sensor that can provide any combination of x, y, or z position information that is better than that obtainable from GPS code phase is a candidate source of such external constraints.
摘要:
A real-time kinematic system includes base and rover GPS units connected by a data link. The rover unit is typically moved to points of interest during a survey while the base remains over a fixed, and known location. An initialization testing program of the present invention is mounted on a personal computer platform that forces in the rover a loss of signal tracking, thus simulating losses in signal reception caused by obstructions of the satellite signals. A complete initialization is forced to occur. The test program uninitializes the RTK solution by causing a loss of integer ambiguities resolution by forcing a loss of lock on one or more satellites. The test program then monitors the subsequent initialization process, e.g., the time needed to search for phase ambiguity candidates, discovering the prevalent satellite geometry, determination of whether the correct ambiguity candidate was found, finding the ratio of the second best to best solution variances of the ambiguity candidates in the list throughout the candidate propagation process or similar statistical test, computing the RMS error of the solution at the time that initialization was declared and after initialization, and calculating the baseline vector between the rover and base at the time of initialization and after initialization. All such statistical parameters are logged and used in post and real-time analyses of the initialization algorithm.
摘要:
A real-time kinematic system includes base and rover GPS units connected by a data link. The rover unit is typically moved to points of interest during a survey while the base remains over a fixed, and known location. An initialization testing program of the present invention is mounted on a personal computer platform that forces in the rover a loss of signal tracking, thus simulating losses in signal reception caused by obstructions of the satellite signals. A complete initialization is forced to occur. The test program uninitializes the RTK solution by causing a loss of integer ambiguities resolution by forcing a loss of lock on one or more satellites. The test program then monitors the subsequent initialization process, e.g., the time needed to search for phase ambiguity candidates, discovering the prevalent satellite geometry, determination of whether the correct ambiguity candidate was found, finding the ratio of the second best to best solution variances of the ambiguity candidates in the list throughout the candidate propagation process or similar statistical test, computing the RMS error of the solution at the time that initialization was declared and after initialization, and calculating the baseline vector between the rover and base at the time of initialization and after initialization. All such statistical parameters are logged and used in post and real-time analyses of the initialization algorithm.
摘要:
A system embodiment of the present invention comprises a fixed and a roving pair of four-observable GPS receivers and a communication link between them for double differencing code and carrier measurements. Carrier phase integer ambiguities are resolved efficiently by searching the simultaneous narrow-lane intersections of both the L1 and L2 wave fronts propagated by the GPS satellites being tracked. External constraint information, such as elevation, is additionally used to speed up integer ambiguity resolution. Data between the reference station and the rover is communicated in compressed form at a regular interval, e.g., once a second at each epoch, and demi-measurements of carrier phase are obtained more frequently, e.g., ten times a second, and used to propagate solutions between epochs.
摘要:
A method for accurately determining the position of a roving receiver positioned on or above the Earth's surface, relative to the position of a reference receiver whose position is known with sufficient accuracy, using measurements of signal phase transmitted at one or more carrier frequencies and received from each of four or more satellites in a Satellite Positioning System (SPS). Phase double differences are formed, using the reference and roving receivers and any two satellites drawn from four or more satellites, using phase information obtained from either or both of the two carrier signal frequencies. Phase correction information, in the form of estimates of integer wavelength ambiguities, is then obtained from two sets of ambiguity estimates computed with the roving receiver antenna in each of two specified positions, with the reference receiver antenna lying between and being collinear with the two roving receiver-antenna positions. If the distance between the reference receiver antenna position and the two roving receiver antenna positions is sufficiently small, a set of estimates at only one of the roving receiver positions may suffice. If an azimuth angle measuring device is incorporated in the apparatus, a set of estimates at only one roving receiver position may again suffice. The method produces a set of simultaneous equations that can be solved for the coordinates of a roving receiver located at an arbitrary position. The reference receiver antenna is positioned at a fixed location and orientation while the roving antenna is correctly positioned at each of two specified locations and orientations. A Global Positioning System (GPS) or a Global Orbiting Navigational System (GLONASS) may serve as the SPS.
摘要:
A system embodiment of the present invention comprises a fixed and a roving pair of four-observable GPS receivers and a communication link between them for double differencing code and carrier measurements. Carrier phase integer ambiguities are resolved efficiently by searching the simultaneous narrow-lane intersections of both the L1 and L2 wave fronts propagated by the GPS satellites being tracked. External constraint information, such as elevation, is additionally used to speed up integer ambiguity resolution. Data between the reference station and the rover is communicated in compressed form at a regular interval, e.g., once a second at each epoch, and demi-measurements of carrier phase are obtained more frequently, e.g., ten times a second, and used to propagate solutions between epochs.
摘要:
A method for accurately determining the position of a roving signal receiver positioned on or above the Earth's surface, relative to the position of a reference receiver whose position is known with sufficient accuracy, using ranging information, transmitted at a pair of predetermined carrier signal frequencies and received from each of n satellites (n.gtoreq.4). Pseudorange double differences are formed, between each of the two receivers and each of a first satellite and the other three satellites, using pseudorange information obtained from either one of the two signal frequencies. Phase correction information, in the form of estimates of integer lane wavelength ambiguities, is then obtained from the pseudorange double differences and from certain measurable phase differences. This products n-1 simultaneous equations that can be solved for the roving receiver position cordinates. The method can be adapted to provide roving receiver position when signals carried by both of the two carrier frequencies are encrypted, where a separate non-encrypted signal is available on one of the two carrier frequencies.