摘要:

A study is conducted to estimate the accurate attitude of a ship's motion and the estimation is used to arrive at the corrections required for a farfield pattern of a coaxial circular array. The relevant analytical expression is developed for the computation of moving average filter weights to estimate the ship's attitude for beamsteerings at different sea conditions. Farfield patterns are presented for different steered directions for the coaxial circular array of the additive type, and the multiplicative array technique is also used for beamsteering for higher steering angles to observe its control on the sidelobes as well as for the main beamwidths. In order to introduce an adaptive filter to estimate the accurate attitude for stable sonar platform, an adaptive parameter is examined for bathymetric applications where nonstationary ship movement prevails.

ISSN:0149-0419    

DOI:10.1080/15210609409379732

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A four‐antenna GPS attitude determination system was used to estimate roll, pitch, and heading parameters of a 52‐meter surveying vessel in an operational marine environment. The least squares algorithm for platform attitude estimation using multiple baseline vector observables is presented. An efficient on‐the‐fly carrier phase ambiguity searching method is derived, which utilizes the Cholesky decomposition method and the known baseline constraints between the GPS antennas to construct the potential ambiguity sets on the sphere. The accuracy of the estimated attitude parameters from the GPS multi‐antenna system was assessed with an independent inertial navigation system (INS). Results from sea trials show that the proposed GPS multi‐antenna system and processing algorithms delivered a satisfactory performance under various ship maneuvers. The accuracy of GPS estimated ship attitude parameters is better than 0.06 degrees at an output rate of 10 Hz. Such a performance demonstrates a new alternative means to provide accurate, reliable, and cost‐effective ship attitude information for hydrographic applications.

ISSN:0149-0419    

DOI:10.1080/15210609409379733

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

At first, the term “accuracy measure”; is described for the one‐dimensional case. Then, the limitations under which conventional methodology of accuracy expressions is useful and the effects of various degrees of assumption failures are examined. Next the criteria of appropriateness, completeness, resistance, and efficiency are set forth as the generic requirements of an investigation into properly selecting scale estimators. Finally, reliable and efficient accuracy measures are proposed for expressing one‐dimensional position uncertainty.

ISSN:0149-0419    

DOI:10.1080/15210609409379734

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Accurate bench marks and water levels, which are important for tidal studies and other hydrographic purposes such as the establishment of chart datums, can be established along river shorelines if an adequate geoid model is available. Differential Global Positioning System (GPS) offers the possibility of determining bench marks and water level profiles with a centimeter‐level accuracy using carrier phase observations, provided that carrier phase ambiguities can be resolved on‐the‐fly. The results of a differential GPS survey conducted with a survey launch along an 80‐km section of the Fraser River, British Columbia, in March 1993 to test this concept are reported. Dual frequency receivers were used to permit quasi‐instantaneous carrier phase ambiguity resolution using widelane observables. Frequent ties to bench marks were made to assess independently the accuracy of the methodology. A 2‐cm accuracy shore‐to‐launch height transfer method that did not require landing of the launch was used. The repeatability of GPS, based on revisits of selected bench marks, was calculated as 5.5 cm RMS. The agreement between GPS‐derived and leveled orthometric heights at bench marks (B.M.’s) was found to be 6.4 cm RMS. This value, which is considered excellent, includes all DGPS error sources and unmodeled geoid biases.

ISSN:0149-0419    

DOI:10.1080/15210609409379735

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Global positioning system (GPS) has found applications in various areas including marine geodesy. GPS positioning accuracy, however, is greatly degraded by GPS ephemeris and clock errors, particularly errors due to Selective Availability (SA). Thus, it is crucial to use precise ephemeris and clock corrections for users who require high position accuracy. Presently, precise ephemeris and clock corrections are available only in post‐mission. This paper investigates the generation of precise real‐time ephemeris and clock corrections and the positioning accuracy using them. In this research, precise real‐time ephemeris is generated from accurate dynamic orbit prediction and clock corrections are calculated using instantaneous GPS measurements. Numerical analysis using data from an actual GPS tracking network is performed that indicates use of precise ephemeris and clock corrections can improve the positioning accuracy to the one meter level. This accuracy is attainable in real‐time as the precise real‐time ephemeris and clock corrections become available in the future.

ISSN:0149-0419    

DOI:10.1080/15210609409379736

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0149-0419    

DOI:10.1080/15210609409379731

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor