This paper presents a low-cost scheme of an autonomous integrated global positioning system (GPS)/geomagnetism navigation system for small satellites to improve the performance of stand-alone GPS or geomagnetism navigation using the existing hardware equipment. In the paper, the use of the GPS and autonomous navigation systems based on magnetic ®eld measurements (ANSMFM) to determine low Earth orbits (LEO) is discussed. The paper combines the GPS with the ANSMFM and constructs a new autonomous GPS/geomagnetism integrated navigation system (AGGINS) using two integration approaches: loosely and tightly coupled integrations. The improved extended Kalman ®lter completes the data processing for the optimal integration. The paper analyses the bene®ts of the AGGINS and ®nally gives simulation results that demonstrate the eectiveness and practicability of the method.
Underwater topography survey is a basics part of hydrological research, and plays an important role in the development of resources in marine lakes and inland rivers. In this paper, the water depth was measured in some waters of Linyi Beng river by using Real time kinematic (RTK) based Qianxun Continuously Operating Reference System (CORS) services and depth sounder, and the underwater topographic map was obtained. In order to test the accuracy of underwater topographic survey, some of the checkpoints were simultaneously observed by the traditional sounding rope method, and the sounding accuracy of these checkpoints was analyzed. The results show that the average accuracy of the sounding with the CORS-RTK+ sounder is 0.12m, compared with the traditional method, which satisfies the accuracy requirements of underwater topography. On this basis, the items that need attention during the practical sounding are given. The above research results can provide a technical reference for underwater topography survey.
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