Automatic-Position-Determination自动定位技术毕业论文外文文献翻译及原文

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　　翻译日期： 2017.02.14

　　Automatic Position Determination

　　1 Position Determination

　　The traditional method for the direct determination of position has been by astronomical observation. The relative positions and movements of the stars as well catalogued and so with a combination of altitude, direction and time observations to the stars, the position in terms of latitude and longitude of a ground station can be calculated. There if less call for direct position determination nowadays since most countries are covered by a primary horizontal control scheme, and the absolute position of any new local survey word can be established by including a national reference point in the local survey.

　　In very remote areas, or where the terrain is totally unsuitable for the classic survey methods of triangulation and traverse, there is, however, a need for direct position determination. For the majority of this work, visual observation to the stars has been replaced by electromagnetic measurements to or from artificial earth satellites. In addition, the relative positions of survey stations can be determined directly by inertial techniques originally developed for aircraft navigation.

　　1.1 Inertial Positioning

　　A pair of gyros are incorporated in a position fixing device known as the Auto-Surveyor manufactured by Litton Systems. It has originated from an aircraft navigation system, which was developed for military applications into its present three-dimensional survey system. ‘Hardware’ consists of (i)the inertial measuring unit, (ii)a computer ,(iii)a cassette recorder,(iv)a display and control unit and (v) the power supply .These items can be placed anywhere within a road vehicle or helicopter providing that the operator is close to (iv).

　　The measuring unit contains a gyro-stabilized platform with two air-bearing gyroscopes in four gimbal mountings which keep its three orthogonal axis oriented in space in a north-east=downwards relationship . Each axis also has a sensor-torquer type of acclerometer which defines acceleration in the particular direction via a quantitizer system feeding the computer .This is pre-programmed to compute the survey as it

　　is carried out and to control the system (see Fig.1)

　　Before staring the survey an alignment drill carried out at the origin station. This is said to have a duration of about one hour (that for the survey is restricted to some four hours or so) and the platform levels itself with respect to the local vertical and aligns its nothing axis with the local meridian so that the