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Yang F.,Key Laboratory of Surveying and Mapping Technology on Island and Reef | Yang F.,Shandong University of Science and Technology | Lu X.,Key Laboratory of Surveying and Mapping Technology on Island and Reef | Lu X.,Shandong University of Science and Technology | And 3 more authors.
OCEANS'10 IEEE Sydney, OCEANSSYD 2010 | Year: 2010

Because of the advantage of acoustic signal traveling in the water, most techniques of precisely locating AUVs adopt GPS and acoustic measurements. The development of modern GNSS techniques, attitude measuring techniques and precise underwater ranging techniques make GPS-acoustic technology possible for accurate localization of an AUV. Because the transmit angles are unknown for transducers, it is complicated for us to solve the coordinates of the AUV. In order to rapidly and accurately obtain the positions of AUV at each epoch, in this paper, an algorithm for locating an AUV in an absolute reference frame is presented. It uses three surface buoys or vessels to range and adopts the iterative resection to solve the position of the AUVs. Acoustic ranges are calculated using the equivalent sound speed profile and travel times of sound rays. This simple equivalent SSP is usually adopted to have a constant gradient in the total water column. Under some approximate conditions, the initial Snell constant can be deduced so that the linear geometric distances can be obtained through ray trace after the Snell constant is iteratively solved. Finally, the precise position of the AUV at each epoch is calculated using the precise geometric distances. It is proved by simulation that this method is capable of real-time positioning of the AUV with an accuracy of ±20cm in the inner cover area of three transducers at a depth of 500m supposing the error of sound speed is 0.1m/s. The precision can be improved further if kalman filter is adopted. © 2010 IEEE.

Cheng C.,Chinese Academy of Surveying and Mapping Beijing | Cheng C.,China University of Mining and Technology | Zhang J.,Chinese Academy of Surveying and Mapping Beijing | Deng K.,China University of Mining and Technology | Zhang L.,Chinese Academy of Surveying and Mapping Beijing
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2010

Imaging equations are always considered as the most essential and basic part in photogrammetry and image mapping with remote sensing images. Rigourism and conciseness should be held as their basic characteristics.In this paper,using sensor exterior orientation including three lines and two attitude elements as the orientation parameters, new imaging equations for side-looking radar or SAR image positioning were derived. The model was based on the distance condition between sensor and object point and the azimuth condition of sensor scanning plane including antenna and radar beam center. Three forms of range-coplanarity equation were derived, the first form was in the tangent plane rectangular coordinate system, the second was in the geocentric rectangular coordinate system, and the third was the range-coplanarity equation with coordinates of image point as explicit function. The model could be easily used for side-looking radar and SAR image processing in photogrammetry field.

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