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1、Chapter 2Coordinate Systems坐坐 标标 系系 统统浙江水利水电专科学校PowerPoint by 僧德文1CHAPTER 2:Coordinate Systems 坐标系统坐标系统Chapter Outline 概要概要2.1 Geographic Coordinate System 地理坐标系统地理坐标系统2.2 Map Projections 地图投影地图投影2.3 Commonly Used Map Projections 常用地图投影常用地图投影2.4 Projected Coordinate Systems 投影坐标系统投影坐标系统2.5 Working w
2、ith Coordinate Systems in GIS 在在GIS中使用坐标系统中使用坐标系统2Basic Principle基本原理基本原理Map layers must align spatially 地图必须以空间排列地图必须以空间排列Concept of registration 注册的概念注册的概念3Figure 2.1The top map shows the road networks in Idaho and Montana based on different coordinate systems.The bottom map shows the road network
3、s based on the same coordinate system.42D versus 3DMaps are two-dimensional 地图是二维的地图是二维的Map feature location identified with x-and y-coordinates 地图要素位置以地图要素位置以 x x 和和 y y 坐标值识别坐标值识别Earths surface is three-dimensional 地球表面是三维的地球表面是三维的Feature location expressed in latitude and longitude 要素位置以经纬度表达要素位置
4、以经纬度表达How do we register the three-dimensional Earth to the two-dimensional map?如何把三维的地球注册成二维的地图？如何把三维的地球注册成二维的地图？How do we register data that comes in different coordinate systems?如何注册不同坐标系统的数据？如何注册不同坐标系统的数据？52.1 Geographic Coordinate System 地理坐标系统地理坐标系统Location reference system for spatial feature
5、s on earths surface 作为地球表面空间要素的位置参照系统作为地球表面空间要素的位置参照系统Angular measurement from an origin to a given point 由原点到特定点的角度测量由原点到特定点的角度测量Latitude(parallels)纬线纬线Longitude(meridians)经线经线Measured in DMS,DD,or radians 以以“度分秒度分秒”、“10进制度进制度”或或“弧度弧度”为量纲为量纲6Figure 2.2The geographic coordinate system.7Figure 2.3A l
6、ongitude reading is represented by a on the left,and a latitude reading is represented by b on the right.Both longitude and latitude readings are angular measures.82.1.1 Approximation of the Earth 地球的近似表示地球的近似表示Shape of Earth not perfectly circularSpheroid(ellipsoid)椭球体椭球体Major axis(a)Minor axis(b)F
7、lattening(f)扁率扁率(a-b)/aGeographic coordinates 地理坐标地理坐标Figure 2.4The flattening is based on the difference between the semimajor axis a and the semiminor axis b.92.1.2 Datum 大地水准面大地水准面Mathematical model of Earth 地球的数学模型地球的数学模型Serves as reference for calculating geographic coordinatesDefinition of a d
8、atum 大地水准面的定义大地水准面的定义origin 坐标原点坐标原点parameters of spheroid 椭球参数椭球参数separation of earth from spheroid at origin 地球与椭球原点的偏离地球与椭球原点的偏离102.1.2 Datum 大地水准面大地水准面Clarke 1866NAD 27NAD 83GRS 80WGS 84Local datums 地方基准地方基准Significance of datum choice 选择基准的意义选择基准的意义 我国我国1980年后采用年后采用“1975年大地坐标系（年大地坐标系（IAG/IUGG)”
9、112.2 Map Projections 地图投影地图投影Conversion(projection)from round Earth(3D)to flat map(2D)从圆的地球到平的地图的转换从圆的地球到平的地图的转换Inherent distortions in the process 投影过程的固有变形投影过程的固有变形Size,shape,distance,direction 大小、形状、距离、方向大小、形状、距离、方向We can preserve one or two of these properties at the expense of the others 可保持其中
10、一两种性质不变而以牺牲其他性质为代价可保持其中一两种性质不变而以牺牲其他性质为代价122.2.1 Projection Types 投影类型投影类型Conformal(true shape)等角等角Equivalent(equal area)等积等积Equidistant 等距等距Azimuthal or true direction 方位角或真方向方位角或真方向Conformal and equivalent mutually exclusive 等角与等积相互排斥等角与等积相互排斥132.2.1 Projection TypesReference globe 参考球体参考球体Cylindr
11、ical 圆柱的圆柱的Conic 圆锥的圆锥的Azimuthal(planar)方位角的（平面的）方位角的（平面的）Hybrid 混合的混合的14Case情景情景Figure 2.6Case and projection.15Aspect朝向朝向Figure 2.7Aspect and projection.162.2.2 Map Projection Parameters 地图投影参数地图投影参数Standard line or point 标准线或点标准线或点Standard parallel 标准纬线标准纬线Standard meridian 标准经线标准经线Principal scal
12、e 主比例尺主比例尺Scale factor 比例因子比例因子17Figure 2.8The central meridian（b)in this secant case transverse Mercator projection has a scale factor of 0.9996.The two standard lines on either side of the central meridian have a scale factor of 1.0.182.3 Commonly Used Map Projections 常用地图投影（中国）常用地图投影（中国）地图投影的选择主要
13、考虑地图的用途、比例尺、区地图投影的选择主要考虑地图的用途、比例尺、区域形状与大小、地理位置及其他特殊要求。域形状与大小、地理位置及其他特殊要求。2.3.1 正轴等面积割圆锥投影正轴等面积割圆锥投影 常用于行政区划图及其常用于行政区划图及其他要求无面积变形的地图他要求无面积变形的地图（如：土地利用图、森林分（如：土地利用图、森林分布图等）。地图出版社出版布图等）。地图出版社出版的中国全图、省区行政区划的中国全图、省区行政区划图均采用之。图均采用之。192.3.2 正轴正轴等角等角割圆锥投影割圆锥投影 标准纬线上无变形，要在图上量测长度和面积，必须标准纬线上无变形，要在图上量测长度和面积，必须进
14、行纠正。进行纠正。常用于我国的地势图与各种气象、气候图，以及各省常用于我国的地势图与各种气象、气候图，以及各省区的地势图。区的地势图。202.3.3 横切横切等角等角椭圆柱投影（高斯椭圆柱投影（高斯-克吕格投影）克吕格投影）该投影是以经差该投影是以经差6度或度或3度为一带投影到椭圆柱面上，然后展开成度为一带投影到椭圆柱面上，然后展开成平面的。中央经线长度不变，其他经线最大长度变形达平面的。中央经线长度不变，其他经线最大长度变形达0.14%，最，最大面积变形达大面积变形达0.27%。在这种图上进行量测精度较高。我国。在这种图上进行量测精度较高。我国1:5000到到1:50万比例尺地形图均采用此投
15、影。万比例尺地形图均采用此投影。212.3 Commonly Used Map Projections （美国）（美国）2.3.1 Transverse Mercator2.3.2 Lambert Conformal Conic2.3.3 Albers Equal-Area Conic2.3.4 Equidistant Conic22Figure 2.10The Mercator and the transverse Mercator projection of the United States.For both projections,the central meridian is 90W
16、 and the latitude of true scale is the equator.23Figure 2.11The Lambert conformal conic projection of the conterminous United States.The central meridian is 96W,the two standard parallels are 33N and 45N,and the latitude of projections origin is 39N.242.4 Projected Coordinate Systems 投影坐标系统投影坐标系统Als
17、o called plane coordinate system 平面坐标系统平面坐标系统Built on specific map projections 建立在特定地图投影上建立在特定地图投影上Designed for detailed calculations and positioning 为详细计算和定位而设计为详细计算和定位而设计Based on two-dimensional cartesian space(x,y coordinates)基于二维迪卡尔空间（基于二维迪卡尔空间（x、y坐标）坐标）25Figure 2.9The central parallel and the c
18、entral meridian divide a map projection into four quadrants.Points within the NE quadrant have positive x-and y-coordinates,points within the NW quadrant have negative x-coordinates and positive y-coordinates,points within the SE quadrant have positive x-coordinates and negative y-coordinates,and po
19、ints within the SW quadrant have negative x-and y-coordinates.The purpose of having a false origin is to place all points within the NE quadrant.伪原点262.4.1 Universal Transverse Mercator (UTM)Grid System2.4.2 Universal Polar Stereographic(UPS)Grid System2.4.3 State Plane Coordinate(SPC)System2.4.4 Pu
20、blic Land Survey System(PLSS)27Figure 2.12UTM zones range from zone 10N to 19N in the conterminous United States.28Figure 2.13A UTM zone represents a secant case transverse Mercator projection.CM is the central meridian,and AB and DE are the standard meridians.The standard meridians are placed 180 k
21、ilometers west and east of the central meridian.Each UTM zone covers 6 of longitude and extends from 84N to 80S.The size and shape of the UTM zone are exaggerated for illustration purposes.29Figure 2.14SPC83 zones in the conterminous United States.The thinner lines are county boundaries,and the gray
22、 lines are state boundaries.This map corresponds to the SPC83 table on the inside of this books back cover.30Figure 2.15The shaded survey township has the designation of T1S,R2E.T1S means that the survey township is south of the base line by one unit.R2E means that the survey township is east of the
23、 Boise(principal)meridian by 2 units.Each survey township is divided into 36 sections.Each section measures 1 mile by 1 mile and has a numeric designation.312.5 Working with Coordinate Systems in GIS 在在GIS中使用坐标系统中使用坐标系统Precisely establishing location 准确建立位置准确建立位置Registration 注册注册2.5.1 Projection Fil
24、e 投影文件投影文件2.5.2 Predefined Coordinate Systems 预定义坐标系统预定义坐标系统2.5.3 On-the-Fly Projection 快速投影快速投影322.5.1 Projection File 投影文件投影文件Text file that stores information on the coordinate system on which the data set is based 储存数据所依据的坐标系统信息的文本储存数据所依据的坐标系统信息的文本332.5.2 Predefined Coordinate Systems 预定义坐标系统预定义
25、坐标系统GIS package groups coordinate systems into predefined and custom GIS GIS 软件包把坐标系统分为预定义的和自定义的软件包把坐标系统分为预定义的和自定义的Predefined means that parameter values are known and already coded into the GIS package 预定义是指参数取值是已知的，并编码到预定义是指参数取值是已知的，并编码到GISGIS软件包软件包342.5.3 On-the-Fly Projection 快速投影快速投影Designed for displaying data sets based on different coordinate systems 为显示基于不同坐标系统的数据集而设计为显示基于不同坐标系统的数据集而设计 Automatically converts data sets to a common coordinate system 自动将数据集转换成共同的坐标系统自动将数据集转换成共同的坐标系统 实质上是两个平面场之间点的坐标变换（基于两实质上是两个平面场之间点的坐标变换（基于两种地图投影点坐标的关系式）种地图投影点坐标的关系式）35