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[注意] 北京54和西安80<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">北京<span lang="EN-US">54</span>和西安<span lang="EN-US">80</span>是我国主要使用的两种坐标系统，它们其实指的是两个<span lang="EN-US">Datum</span>的概念。因此，北京<span lang="EN-US">54</span>和西安<span lang="EN-US">80</span>即可以指大地坐标系统（<span lang="EN-US">GCS</span>），又可以指投影坐标系统（<span lang="EN-US">PCS</span>）。我们先来看看<span lang="EN-US">ArcGIS</span>中对于北京<span lang="EN-US">54</span>在<span lang="EN-US">GCS</span>中的定义：</span><span style="FONT-FAMILY: 宋体; COLOR: #555555; FONT-SIZE: 9pt" lang="EN-US"><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p></span></p> <p style="LINE-HEIGHT: 22.5pt; TEXT-INDENT: 24pt; WORD-BREAK: break-all" class="MsoNormal"><span style="FONT-FAMILY: 宋体; COLOR: black; mso-bidi-font-family: Arial" lang="EN-US">Angular Unit: Degree (0.017453292519943299)<br/>Prime Meridian: Greenwich (0.000000000000000000)<br/>Datum: D_Beijing_1954<br/></span><span style="FONT-FAMILY: 宋体; COLOR: black; mso-bidi-font-family: Arial"> <span lang="EN-US"> Spheroid: Krasovsky_1940<br/></span> <span lang="EN-US"> Semimajor Axis: 6378245.000000000000000000<br/></span> <span lang="EN-US"> Semiminor Axis: 6356863.018773047300000000<br/>Inverse Flattening: 298.300000000000010000</span></span><span style="FONT-FAMILY: 宋体; COLOR: #555555; FONT-SIZE: 9pt; mso-bidi-font-family: Arial" lang="EN-US"><o:p></o:p></span></p> <p style="LINE-HEIGHT: 22.5pt; TEXT-INDENT: 24pt; WORD-BREAK: break-all" class="MsoNormal"><span style="FONT-FAMILY: 宋体; COLOR: black; mso-bidi-font-family: Arial">可以看到，<span lang="EN-US">Datum</span>是<span lang="EN-US">D_Beijing_1954</span>。北京<span lang="EN-US">54</span>使用的是克拉索夫斯基椭球，大地原点在西伯利亚。而西安<span lang="EN-US">80</span>使用的是<span lang="EN-US">IAG 75</span>椭球，大地原点在陕西泾阳。再来看北京<span lang="EN-US">54</span>在<span lang="EN-US">PCS</span>中的定义：</span><span style="FONT-FAMILY: 宋体; COLOR: #555555; FONT-SIZE: 9pt; mso-bidi-font-family: Arial" lang="EN-US"><o:p></o:p></span></p> <p style="LINE-HEIGHT: 22.5pt; TEXT-INDENT: 24pt; WORD-BREAK: break-all" class="MsoNormal"><span style="FONT-FAMILY: 宋体; COLOR: black; mso-bidi-font-family: Arial" lang="EN-US">Projection: Gauss_Kruger<br/>False_Easting: 500000.000000<br/>False_Northing: 0.000000<br/>Central_Meridian: 117.000000<br/>Scale_Factor: 1.000000<br/>Latitude_Of_Origin: 0.000000<br/>Linear Unit: Meter (1.000000)<br/></span><span style="FONT-FAMILY: 宋体; COLOR: black; mso-bidi-font-family: Arial"> </span><span style="FONT-FAMILY: 宋体; COLOR: #555555; mso-bidi-font-family: Arial" lang="EN-US"><br/></span><span style="FONT-FAMILY: 宋体; COLOR: black; mso-bidi-font-family: Arial" lang="EN-US">Geographic Coordinate System: GCS_Beijing_1954<br/>Angular Unit: Degree (0.017453292519943299)<br/>Prime Meridian: Greenwich (0.000000000000000000)<br/>Datum: D_Beijing_1954<br/></span><span style="FONT-FAMILY: 宋体; COLOR: black; mso-bidi-font-family: Arial"> <span lang="EN-US"> Spheroid: Krasovsky_1940<br/></span> <span lang="EN-US"> Semimajor Axis: 6378245.000000000000000000<br/></span> <span lang="EN-US"> Semiminor Axis: 6356863.018773047300000000<br/>Inverse Flattening: 298.300000000000010000</span></span><span style="FONT-FAMILY: 宋体; COLOR: #555555; FONT-SIZE: 9pt; mso-bidi-font-family: Arial" lang="EN-US"><o:p></o:p></span></p> <p class="MsoNormal"><span style="FONT-FAMILY: 宋体; COLOR: black; mso-bidi-font-family: Arial">可以看到，一个<span lang="EN-US">PCS</span>必然包含一个<span lang="EN-US">GCS</span>的定义，也就是说<span lang="EN-US">PCS=GCS+</span>地图投影。我国的基本比例尺地形图<span lang="EN-US">(1:5</span>千，<span lang="EN-US">1:1</span>万，<span lang="EN-US">1:2.5 </span>万，<span lang="EN-US">1:5</span>万，<span lang="EN-US">1:10</span>万，<span lang="EN-US">1:25</span>万，<span lang="EN-US">1:50</span>万，<span lang="EN-US">1:100</span>万<span lang="EN-US">)</span>中，大于等于<span lang="EN-US">50</span>万的均采用高斯<span lang="EN-US">-</span>克吕格投影，又叫横轴墨卡托投影<span lang="EN-US"> (Transverse Mercator)</span>；小于<span lang="EN-US"> 50</span>万的地形图采用正轴等角割圆锥投影，又叫兰勃特投影<span lang="EN-US">(Lambert Conformal Conic)</span>；海上</span><span style="FONT-FAMILY: 宋体; COLOR: black; FONT-SIZE: 9pt; mso-bidi-font-family: Arial" lang="EN-US"><br/></span><span style="FONT-FAMILY: 宋体; COLOR: black; mso-bidi-font-family: Arial">小于<span lang="EN-US">50</span>万的地形图多用正轴等角圆柱投影，又叫墨卡托投影<span lang="EN-US">(Mercator)</span>。在<span lang="EN-US">ArcGIS</span>软件中，北京<span lang="EN-US">54</span>和西安<span lang="EN-US">80</span>的<span lang="EN-US">PCS</span>坐标都是使用高斯<span lang="EN-US">-</span>克吕格投影。</span><span style="FONT-FAMILY: 宋体" lang="EN-US"><o:p></o:p></span></p> <p class="MsoNormal"><span style="FONT-FAMILY: 宋体" lang="EN-US"><o:p> </o:p></span></p> |
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1楼#
发布于：2013-04-02 14:54
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体; COLOR: black; mso-bidi-font-size: 10.5pt">为了方便大家读懂，特意名词解释一下：<span lang="EN-US"><br/></span>高斯克吕格<span lang="EN-US"><br/></span>（<span lang="EN-US">1</span>）高斯克吕格投影<span lang="EN-US"><br/></span>高斯<span lang="EN-US">-</span>克吕格投影是等角横轴切圆柱投影，该投影按照投影带中央子午线投影为直线且长 度不变和赤道投影为直线的条件，确定函数的形式，从而得到高斯<span lang="EN-US">- </span>克吕格投影公式。投影 后，除中央子午线和赤道为直线外，其他子午线均为对称于中央子午线的曲线。设想用一个 圆柱横切于椭球面上投影带的中央子午线，按上述投影条件，将中央子午线两侧一定经差范围内的椭球面投影于圆柱面。将圆柱面沿过南北极的母线剪开展平，即为高斯投影平面。取 中央子午线与赤道交点的投影为原点，中央子午线的投影为纵坐标<span lang="EN-US">x</span>轴，赤道的投影为横坐标<span lang="EN-US"> y</span>轴，构成高斯克吕格平面直角坐标系。<span lang="EN-US"><br/></span>（<span lang="EN-US">2</span>）高斯克吕格分带<span lang="EN-US"><br/></span>高斯<span lang="EN-US">-</span>克吕格投影在长度和面积上变形很小，中央经线无变形，自中央经线向投影带边缘 ，变形逐渐增加，变形最大之处在投影带内赤道的两端。为了减少投影后的变形，高斯克吕格采用了分带投影的方式，有<span lang="EN-US">6</span>度分带和<span lang="EN-US">3</span>度分带两种。<span lang="EN-US">6</span>度带自<span lang="EN-US">0</span>度子午线起每隔经差<span lang="EN-US">6</span>度自西向东分带，带号依次编为第<span lang="EN-US"> 1</span>、<span lang="EN-US">2…60</span>带。<span lang="EN-US">3</span>度带是在<span lang="EN-US">6</span>度带的基础上分成的，它的中央 子午线与六度带的中央子午线和分带子午线重合，即自<span lang="EN-US"> 1.5</span>度子午线起每隔经差<span lang="EN-US">3</span>度自西向东 分带，带号依次编为三度带第<span lang="EN-US"> 1</span>、<span lang="EN-US">2…120</span>带。我国的经度范围西起<span lang="EN-US"> 73°</span>东至<span lang="EN-US"> 135°</span>，可分成六度带十一个，各带中央经线依次为<span lang="EN-US">75°</span>、<span lang="EN-US">81°</span>、<span lang="EN-US">87°</span>、<span lang="EN-US"> ……</span>、<span lang="EN-US">117°</span>、<span lang="EN-US">123°</span>、<span lang="EN-US">129°</span>、<span lang="EN-US">135°</span>，或三度带二十二个。六度 带可用于中小比例尺（如<span lang="EN-US"> 1</span>：<span lang="EN-US">250000</span>）测图，三度带可用于大比例尺（如<span lang="EN-US"> 1</span>：<span lang="EN-US">10000</span>）测图， 城建坐标多采用三度带的高斯投影。<span lang="EN-US"><br/></span>（<span lang="EN-US">3</span>）高斯克吕格坐标<span lang="EN-US"><br/></span>高斯克吕格坐标中，纵坐标以赤道为零起算，赤道以北为正，以南为负。我国位于北半球 ，纵坐标均为正值。横坐标如以中央经线为零起算，中央经线以东为正，以西为负，为了避免横坐标出现负值，故规定将坐标纵轴西移<?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:chmetcnv w:st="on" tcsc="0" numbertype="1" negative="False" hasspace="False" sourcevalue="500" unitname="公里"><span lang="EN-US">500</span>公里</st1:chmetcnv>当作起始轴，凡是带内的横坐标值均加<span lang="EN-US"> <st1:chmetcnv w:st="on" tcsc="0" numbertype="1" negative="False" hasspace="False" sourcevalue="500" unitname="公里">500<span lang="EN-US"><span lang="EN-US">公里</span></span></st1:chmetcnv><span lang="EN-US">。由于高斯-</span></span>克吕格投影每一个投影带的坐标都是对本带坐标原点的相对值，所以各 带的坐标完全相同，为了区别某一坐标系统属于哪一带，在横轴坐标前加上带号，如<span lang="EN-US"> (<st1:chmetcnv w:st="on" tcsc="0" numbertype="1" negative="False" hasspace="False" sourcevalue="4231898" unitname="m">4231898m</st1:chmetcnv>,<st1:chmetcnv w:st="on" tcsc="0" numbertype="1" negative="False" hasspace="False" sourcevalue="21655933" unitname="m">21655933m</st1:chmetcnv>)</span>，其中<span lang="EN-US">21</span>即为带号。<span lang="EN-US"><br/></span>（<span lang="EN-US">4</span>）<span lang="EN-US">ArcGIS</span>中的描述<span lang="EN-US"><br/></span>下面以北京<span lang="EN-US">54</span>为例，来说明<span lang="EN-US">ArcGIS</span>中对于高斯克吕格这种投影坐标的描述：<span lang="EN-US"><br/>Beijing 1954 3 Degree GK CM 75E.prj<br/>Beijing 1954 3 Degree GK Zone 25.prj<br/>Beijing 1954 GK Zone 13.prj<br/>Beijing 1954 GK Zone 13N.prj<br/></span>它们分别指的是：<span lang="EN-US"><br/></span>三度分带法的北京<span lang="EN-US">54</span>坐标系，中央经线在东<span lang="EN-US">75</span>度的分带坐标，横坐标前不加带号；<span lang="EN-US"><br/></span>三度分带法的北京<span lang="EN-US">54</span>坐标系，中央经线在东<span lang="EN-US">75</span>度的分带坐标，横坐标前加带号；<span lang="EN-US"><br/></span>六度分带法的北京<span lang="EN-US">54</span>坐标系，分带号为<span lang="EN-US">13</span>，横坐标前加带号；<span lang="EN-US"><br/></span>六度分带法的北京<span lang="EN-US">54</span>坐标系，分带号为<span lang="EN-US">13</span>，横坐标前不加带号。<span lang="EN-US"><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p></span></span></p> <p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p> |
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