GPS测量的基本概念.ppt

Basic Concepts For GPS Surveying GPS测量的 基本概念 GPS测量 导航卫星GPS GPS坐标 参考高程 GPS测量类型 静态 快速静态 动 态 后处理动态 实时动态 GPS (The Global Positioning System) 全 球 定 位 系 统 GPS 坐 标 系 地球质心为原点的坐标系统（直角坐标系） Ellipse in 3-D: 三维椭球 直角坐标系和大地坐标系  直角坐标(X,Y,Z) 大地坐标（f,l,H） 参 考 平 面 不同的水准面 GPS参考高程 GPS 不同水准面 大地水准面和椭球面之差 GPS 确 定 海 拔 高 局部椭球数学模型 GPS 向 量： GPS 卫 星 信 号 特 征 整 周 模 糊 度 整 周 模 糊 度 GPS测量条件 至少需要两台接收机 须跟踪锁定四颗分布良好的卫星 数据接收必需同步 Conditions for surveying with GPS测量条件 接收机必须有较强的接收波段的能力（不仅仅是C/A码） 至少一个点的坐标是已知的 在坐标转换时需两个平面控制点和三个高程控制点七个控制参数 测量方法 静态测量 快速静态 动态测量 后处理 实时 静态测量（一） 静态测量（二） 快速静态测量 动态 (后处理一) 动态 (后处理二) 动态（实时一） 动态（实时二） 3 This slide shows the three distinct segments of GPS, the Control Segment, the Space Segment, and the User Segment. If one of these segments did not operate, you would not be able to use GPS. Satellite information and orbital corrections are sent UP to the satellites from the control segment, and the satellites provide the necessary information to obtain positions on the earth as well as relative baselines between points 4 5 The GPS Satellites are rotating about a fixed Cartesian Axis System, where each satellite at any epoch (or “snapshot”) in time has a unique X, Y, and Z value. This ECEF coordinate system is used in GPS computations to provide a position on the earth in terms of something we can understand more clearly, such as latitude, longitude, and height. This can be later translated into N, E, Elev. by use of a user defined projection. 6 If we rotate an ellipse about the Z axis of the ECEF Coordinate System, we can obtain an “ellipsoid of revolution”, as shown in this slide. There are many ellipsoids that represent the size and shape of the earth, but the fundamental GPS ellipsoid that is used is the World Geodetic System 84 Ellipsoid (WGS-84). The elements of this ellipsoid are as follows: Latitudes, Longitudes, and Heights are given by a GPS receiver unless a “Datum Transformation” is applied. Parameters for the Datum transformation are provid