排序方式： 共有40条查询结果，搜索用时 31 毫秒
1.
An algorithm for considering time-correlated errors in a Kalman filter is presented. The algorithm differs from previous implementations
in that it does not suffer from numerical problems; does not contain inherent time latency or require reinterpretation of
Kalman filter parameters, and gives full consideration to additive white noise that is often still present but ignored in
previous implementations. Simulation results indicate that the application of the new algorithm yields more realistic and
therefore useful state and covariance information than the standard implementation. Results from a field test of the algorithm
applied to the problem of kinematic differential GPS demonstrate that the algorithm provides slightly pessimistic covariance
estimates whereas the standard Kalman filter provides optimistic covariance estimates. 相似文献
2.
Shipborne GPS attitude determination during MMST-93 总被引：1，自引：0，他引：1
Lachapelle G. Cannon M.E. Lu G. Loncarevic B. 《Oceanic Engineering, IEEE Journal of》1996,21(1):100-104
The attitude parameters of a ship underway were measured using a configuration of four 10-channel NovAtel Model 951 narrow-correlator-spacing receivers. These C/A code receivers have output rates of up to 10 Hz and maintain effective carrier phase lock under relatively harsh ship dynamics. The attitude parameters are calculated independently at each epoch using differential carrier phase measurements, carrier phase ambiguities are resolved on-the-fly by constraining the approximately known distances between the antennas that are rigidly mounted on the ship. Carrier phase thermal noise and multipath are minimized by mounting the antennas as far apart as possible. The four-antenna configuration provides redundancy and further improves accuracy. During the Matthew Motion Sensor Trials (MMST-93) conducted off the coast of Halifax, Nova Scotia, in June-July 1993, the GPS-derived attitude parameters were compared with those obtained with a Honeywell HG1050 ring laser gyro inertial navigation system (INS) which provides roll and pitch with an accuracy of 15 arcsecs and heading with an accuracy of 2 arcmins. To simulate rough weather conditions, sharp maneuvers were performed to induce roll angles in excess of 10°. No accuracy degradation nor any loss of GPS measurements occurred. The RMS agreement between GPS and INS derived attitude parameters is better than 2 arcmins in heading, 1 arcmin in pitch and 3 arcmins in roll. This level of accuracy demonstrates the capability of GPS for cost-effective shipborne attitude determination at an accuracy level of 0.05 相似文献
3.
Carrier phase ambiguity resolution on the fly is investigated using two receiver technologies, namely dual-frequency P code and high performance, single frequency, C/A code receivers. Both receiver types were used simultaneously in a series of land kinematic trials. A least-squares search technique is used to find the correct double difference carrier phase ambiguities. Both C/A and single frequency P code technologies are found to be equivalent and capable of resolving the integer ambiguities on the fly using some 30 to 200 seconds of data under benign multipath conditions. Successful ambiguity resolution on the fly results in cm-level accuracy kinematic positioning. The ambiguity resolution time required and success rate are however found to be strongly dependent on the level of carrier phase multipath and, as a consequence, on the error variance assigned to the carrier phase measurements. The use of widelaning with the dual frequency P code results in ambiguity resolution in seconds. The performance of widelaning is also superior in a comparatively high carrier phase multipath environment. 相似文献
4.
A least-squares prediction method is described to estimate horizontal coordinate distortions at lower order points of a network
using known coordinate differences (NAD27 coordinate distortions Δϕ′s and Δλ′s) at higher order points between NAD27 coordinates
and coordinates derived from a recent (MAY 76), relatively distortion free, adjustment of these points. Empirical autocovariance
functions of Δϕ and Δλ and crosscovariance function between Δϕ and Δλ are derived from some 5,250 data points and modelled
using series of exponential functions. Empirical mean square values of Δϕ and Δλ, which are a measure of the distortions in
NAD27 ϕ and λ, are 0.051 and 0.645 arcsecs2 respectively. The corresponding mean value of the product ΔϕΔλ, which is a measure of the correlation between Δϕ and Δλ,
is 0.056 arcsecs2. The accuracy obtainable for predicted Δϕ and Δλ at an arbitrary point (e.g., lower order station) is a function of the accuracy
and configuration of known Δϕ′s and Δλ′s in the surrounding area. Accuracies obtainable for various types of data configuration
are given. Under favorable conditions taking place in about 60% of cases, accuracies in terms of ms agreement with known values
of 0″.02 (0.6 m) and 0″.01 (0.2 m along parallel at latitude 50°) for the predicted latitude and longitude distortions are
obtainable. Finally, a comparison with a method based on the use of complex polynomials is made.
Presented at International Symposium on Geodetic Networks and Computations, Munich, August–September 1981. 相似文献
5.
This paper is aimed at investigating the stability of point positions over time in support of applications that require high
position stability when differential GPS is not feasible. One such application is the use of a P3-Orion aircraft offshore
for magnetic measurement in support of submarine detection. Temporal changes in several GPS errors lead to variability in
the computed positions, so it is not the absolute errors, but rather their temporal variations that are of importance. Furthermore,
the temporal variability of the different error sources may dictate a certain algorithm approach and processing strategy.
This paper analyzes the temporal variations of the broadcast satellite clock model and orbit parameters, as well as ionospheric
errors, because these will typically be the dominant errors for real-time point positioning. These three errors are analyzed
independently. A tropospheric correction is applied when computing all of the position results, so the tropospheric error
itself is not investigated. Satellite clock and orbit errors are analyzed by comparing broadcast and precise post-mission
SV clock corrections and orbits. For the ionosphere, the effect is separated using dual-frequency data. The analysis comprises
primarily of assessing error behaviors and magnitudes through time and frequency analyses. In this way, the differences in
variability of the errors are easily determined. The effect of each error in the position domain is also investigated in addition
to the combined effect. Results show that, on a typical day when single frequency data are processed with broadcast orbit
and clock data, the root mean square (RMS) of the changes in the position errors over a 50-s interval is about 5.8 cm in northing,
4.0 in easting, and 11.0 cm in height. When using precise orbits and clocks, in addition to dual frequency data, these values
improve by 46–56% to 2.7 cm in northing, 2.2 cm in easting, and 4.9 cm in height. Under severe ionospheric activity, the RMS
of the errors decrease from 8.1 to 3.3 cm in northing, 5.7 to 2.6 cm in easting, and 17.0 to 4.9 cm in height, which are improvements
of 54–71%.
Electronic Publication 相似文献
6.
Precise aircraft single-point positioning using GPS post-mission orbits and satellite clock corrections 总被引：3，自引：0，他引：3
Summary Aircraft single point position accuracy is assessed through a comparison of the single point coordinates with corresponding DGPS-derived coordinates. The platform utilized for this evaluation is a Naval Air Warfare Center P-3 Orion aircraft. Data was collected over a period of about 40 hours, spread over six days, off Florida's East Coast in July 94, using DGPS reference stations in Jacksonville, FL, and Warminster, PA. The analysis of results shows that the consistency between aircraft single point and DGPS coordinates obtained in single point positioning mode and DGPS mode is about 1 m (rms) in latitude and longitude, and 2 m (rms) in height, with instantaneous errors of up to a few metres due to the effect of the ionosphere on the single point L1 solutions. 相似文献
7.
8.
There is an emerging requirement for processing global navigation satellite system (GNSS) signals indoor where the signal
is very weak and subjected to spatial fading. Typically, longer coherent integration intervals provide the additional processing
gain required for the detection and processing of such weak signals. However, the arbitrary physical motion of the handset
imputed by the user limits the effectiveness of longer coherent integration intervals due to the spatial decorrelation of
the multipath-faded GNSS signal. In this paper, limits of coherent integration due to spatial decorrelation are derived and
corroborated with experimental verification. A general result is that the processing gain resulting from direct coherent integration
saturates after the antenna has moved through a certain distance, which for typical indoor propagation, is about half a carrier
wavelength. However, a refined Doppler search coupled with a prolonged coherent integration interval extends this limit, which
is effectively a manifestation of selective diversity. 相似文献
9.
A Kalman filter-based method combining the energy of both L1 C/A and L2C GPS signals in a combined tracking loop method to
enhance performance under adverse conditions is developed. Standard tracking methods and the ionospheric effect on GPS signals
are reviewed and compared to a new Kalman filter that simultaneously estimates delay, phase and total electron content by
combining L1 C/A and L2C code and phase discriminator outputs. The new filter is tested and compared to standard methods for
tracking L1 C/A and L2C using both simulated and real data. The new method is found to have improved sensitivity of 3 dB compared
to standard L1 tracking and 4.5 dB compared to standard L2C tracking while at the same time providing an accurate estimate
of the total electron content along the signal path. 相似文献
10.