1 Topic:Specifying a coordinate system
主题：指定个坐标系统
Release 9.2
发表：9.2版本
Last modified November 7, 2007
最后修改时间：11月，7日，2007年
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About coordinate systems and map projections
关于坐标系统和地图投影
Defining a coverage's coordinate system
定义某个coverage的坐标系统
Defining a shapefile's coordinate system
定义个某个shapefile的坐标系统
2 About specifying a coordinate system
关于指定（/声明）一个坐标系统。
If all the data you want to display on your map is stored in the same coordinate system—for example, if you're using your organization's database—you can just add it to a map and not consider whether the layers will overlay properly; they will. If, however, you've collected data from a variety of sources, you'll need to know what coordinate system each dataset uses to ensure ArcMap can display them together.
如果你要在你的地图中显示的所有数据存储于同一坐标系统之下——例如，你在使用你的组织（｜中国人通常称为单位、机关）的数据库——你正好能添加它到一个地图而不用考虑那个图层是否会被正确的覆盖；它们会。如果，无论如何，你从多个数据源收集到的数据，你将需要知道每个数据集使用什么坐标系统以确保ArcMap能一起（/同时）显示他们。
For more information on coordinate systems, see Map projections and coordinate systems.
更多关于坐标系统的信息，参见“地图投影和坐标系统”
coordinate system
坐标系统
A reference framework consisting of a set of points, lines, and/or surfaces, and a set of rules, used to define the positions of points in space in either two or three dimensions. The Cartesian coordinate system and the geographic coordinate system used on the earth's surface are common examples of coordinate systems.
由一套点、线和/或面，和一套规则构成的参考框架，用于定义任意二维或三维的空间的点的位置。用于地球表面的笛卡尔坐标系统和地理坐标系统是坐标系统的通用例子。
2.1 Coordinate systems and data frames
坐标系统和数据框
To display your data correctly, a data frame uses a coordinate system. This can be any coordinate system ArcGIS supports. The data frame's coordinate system need not be the same as the data you are using, although if ArcMap has to project your data on the fly, it does take longer to draw.
要正确的显示你的数据，一个数据框使用一个坐标系统。这个可以是任意ArcGIS支持的坐标系统。数据框的坐标系统不需要同你使用的数据（的坐标系统）相同，然而，如果ArcMap要即时投影你的数据，它需要更长的时间才能得出（提取｜逗号后面这点儿是Google翻译的）。
When ArcMap is started with a new, empty map, the coordinate system for the default data frame is not defined. When you add data with a defined coordinate system, ArcMap will automatically set the data frame's projection to be the same as that of the data. The first layer added to an empty data frame sets the coordinate system for the data frame, but you can change it if necessary. If the first layer does not have a coordinate system, ArcMap will set the coordinate system to Unknown.
当ArcMap以一个新的、空白的地图启动，默认的数据框的坐标系统并没有定义。当您添加一个定义了坐标系统的数据时，ArcMap将自动设置数据框的投影与那个数据（的坐标系统）相同。添加到一个空数据框的第一个层设置数据框的坐标系统，但如果需要你可以改变它。如果第一个层没有坐标系统，ArcMap将设置坐标系统为Unknown。
As you add subsequent layers, they are automatically transformed to the data frame's coordinate system as long as there's enough information associated with the layer's data source to determine its current coordinate system. If there isn't enough information, ArcMap will be unable to align the data and display it correctly. In this case, you'll have to supply the necessary coordinate system information yourself.
当你添加随后的层时，它们被自动转换到数据框的坐标系统，只要那有足够的与层的数据源相联系的信息来确定它当前的坐标系统。如果没有足够的信息，ArcMap将不能校正数据和正确的显示它。既然这样，你将需要自己提供必需的坐标系统信息。
When the data frame's coordinate system is unknown, you may set the map units (on the General tab of the Data Frame Properties dialog box), provided you know the units of the coordinate system in which the data is stored. Generally, if you have data that does not have a coordinate system defined and you know which coordinate system it is using, you should use the Define Projection tool in ArcToolbox to assign projection information to your data; this will make working with that data in ArcMap much easier.
当数据框的坐标系统为Unknown时，你可以设置图距单位（在Data Frame Properties对话框的General标签中），条件是你知道那个已经存储的数据的坐标系统的单位。一般情况下，如果你有数据，它没有被定义一个坐标系统而且您知道它使用使用哪个坐标系统，你能使用ArcToolbox中的Define Projection工具来指定投影信息到你的数据。这将使在ArcMap中通过这个数据的工作非常容易。
If you want to use a specific coordinate system for your map, you can use the Data Frame Properties dialog box to set the coordinate system. Once you do this or if ArcMap has already automatically defined the coordinate system for a data frame, ArcMap will not override the coordinate system settings.
如果你想为你的地图使用一个具体（相对于一般特殊的、明确的）的坐标系统，您能使用Data Frame Properties 对话框来设置坐标系统。一旦你这样做或如果ArcMap已经自动为一个数据框定义了坐标系统，ArcMap不会忽略坐标系设置（Yahoo翻译的）。
data frame
数据框
A map element that defines a geographic extent, a page extent, a coordinate system, and other display properties for one or more layers in ArcMap. A dataset can be represented in one or more data frames. In data view, only one data frame is displayed at a time; in layout view, all a map's data frames are displayed at the same time. Many cartography texts use the term "map body" to refer to what ESRI calls a data frame.
一个地图要素，它定义了一个地理范围，一个页面范围、一个坐标系统和其它ArcMap中的一个或多个显示属性。一个数据组（｜数据集）可以表现到一个或多少数据框。在数据视图，一次只有查看一个数据组；在布局视图，同时显示一个地图的所有数据框。一些地图制作课本使用学术“map body（｜地图正文）就是指的ESRI所称的数据框。
projection
投影
A method by which the curved surface of the earth is portrayed on a flat surface. This generally requires a systematic mathematical transformation of the earth's graticule of lines of longitude and latitude onto a plane. Some projections can be visualized as a transparent globe with a light bulb at its center (though not all projections emanate from the globe's center) casting lines of latitude and longitude onto a sheet of paper. Generally, the paper is either flat and placed tangent to the globe (a planar or azimuthal projection) or formed into a cone or cylinder and placed over the globe (cylindrical and conical projections). Every map projection distorts distance, area, shape, direction, or some combination thereof.
是一种方法，通过它地球的弯曲表面被描绘于一个平坦的表面。这通常需要在一个在某个平面一个地球丝网的系统的数学的转换。一些投影能形象的表示为一个透明的地球和一个放置于中心的灯泡（并不是所有的投影都是从地球的中心散发），投射经纬度到一页纸。通常纸为任意平面而且正切于地球（平面或方位角投影）或被做成圆锥或圆筒放置于地球外（圆柱或圆锥投影）。每个地图投影都弯曲距离、面积、形状、方向或它们的组合。
2.2 Map units
The map units are the units in which the spatial data in the data frame is drawn. The map units are determined by the coordinate system specified on the Coordinate System tab of the Data Frame Properties dialog box. The Map Units drop-down list is disabled once a coordinate system has been specified; map units cannot be changed once a coordinate system has been specified for the map.
图距单位是被制图于数据框中的空间数据中的单位。图距单位视在Data Frame Properties 中坐标系统标签被指定的坐标系统而定。一旦一个坐标系统被指定，图距单位列表就会被显示；一旦某个地图被指定一个坐标系统，图距单位就不能被改变。
The map units will be shown as unknown if no coordinate system has been specified for the data frame, or if the coordinate system is unknown because the data in your map doesn't have spatial reference information. When the map units are unknown, you should either specify a coordinate system for the data frame or—if the data frame contains no data—add your first layer to the data frame, which will set the coordinate system automatically if the data has spatial reference information. In some situations, you can set the map units manually. For example, you can specify what the map units will be in for any graphics you draw or features that you edit.
如果没有一个坐标系统指定给数据框或者因为您的地图中的数据没有空间参考信息而使得坐标系统未知，图距单位将显示为“unknown”。当图距单位为Unknown，你该，或者为数据框指定一个坐标系统或者——如果数据框不包含数据——添加你的第一个层（｜数据）到数据框，如果数据有空间参考信息它将自动设置坐标系统。在一些情境下，你可以手动设置图距单位。例如，你可以指定什么图距单位将显示在一些您画的图或您编辑的要素。
2.3 How coordinate system information for a data source is stored
一个数据源的坐标系统信息是如何存储的？
ArcMap expects coordinate system information to be stored with the data source. For a layer in a geodatabase, this information is part of the layer's metadata and is stored in the geodatabase. For shapefiles, it's stored on disk in a separate file named after the data source but with a .prj file extension, for example, streets.prj. Coverages and ESRI Grids store the coordinate information in a .prj.adf file located in the data source's folder. Other raster formats store the coordinate system information in the .aux file or the raster header (the beginning of the raster file). These files are optional files; and you may still need to define the coordinate system for one of these data sources. You can define a coordinate system using ArcCatalog or with geoprocessing tools.
ArcMap认为（｜默认）坐标系统信息与数据源一起存储。对一个地理数据库的一个层，这个信息是层的元数据的一部分并存储于地理数据库。对于一个Shapefiles文件，则以数据源的名字命名、但以a.prj为扩展名的单独文件存储于磁盘，例如，streets.prj。Coverages 和ESRI Grids 存储坐标信息在一个a.prj.adf文件装载在数据源文件夹。其它删格格式存储其坐标系统信息在一个.aux 文件或栅格（｜文件）头部（栅格文件的开始部分）。这个文件是可选(|非强制性的）文件；而且你可能仍然需要为一个这个数据源的一个定义坐标系统。你能使用ArcCatalog或geoprocessing工具来定义一个坐标系统。
Learn how to define a shapefile's coordinate system
Learn how to define a coverage's coordinate system
If no coordinate system information is associated with a data source, ArcMap will examine the coordinate values to see if they fall within the proper range: -180 to 180 for x-values and -90 to 90 for y-values. If they do, ArcMap assumes that these are geographic coordinates of latitude and longitude. If they don't, ArcMap simply treats the values as planar x,y coordinates. The map and display units are set to Unknown.
如果数据源没有被坐标系统联系，如果它们在适当的范围：X值在-１８０到１８０,Y值在-90到90,ArcMap将审查坐标值来查看。如果是这样，ArcMap认为这里有经度和纬度的地理坐标。如果不是，ArcMap简单的看作坐标值为平面XY坐标。地图和显示单位设置为“Unknown”。
3 How to specify a coordinate system
如何指定一个坐标系统
3.1 Setting a data frame's coordinate system
设置数据框的坐标系统
Right-click the data frame in the table of contents and click Properties.
在内容表中右击数据框再单击属性
Click the Coordinate System tab on the Data Frame Properties dialog box.
在“数据框属性”对话框中单击“坐标系统”标签
Choose a coordinate system from the tree or click the Import button and browse to a data source that is defined with the coordinate system you want to use.
在树中选择一个坐标系统或单击“输入”按钮定位到一个定义了你想使用的坐标系统的数据源。
Once you have chosen a coordinate system, its parameters are displayed in the Current coordinate system box.
一旦您选择了一个坐标系统，它的参数就显示于“当前坐标系统”框中。
Click OK.
单击OK。
Tip
提示
To set the coordinate system of a data frame you must not currently be editing, since changing the coordinate system used by your map while you are editing could introduce alignment and accuracy problems. To end your editing session, click Stop Editing from the Editor menu.
要设置一个数据框的坐标系统你不能正在编辑它，此前更改的坐标系统被应用于您的地图，当您编辑的时候可能导致对齐或精确性问题。要结束你的编辑过程，从“编辑”菜单中单击“结束编辑”。
3.2 Finding out what coordinate system your data is currently displayed with
找出您的数据当前显示于什么坐标系统
Right-click the data frame for which you want to determine the coordinate system and click Properties.
右击你要确定坐标系统的数据框再单击属性
Click the Coordinate System tab.
单击坐标系统标签
The details of the current data frame coordinate system display on the dialog box.
当前数据框坐标系统的详细信息显示在对话框中。
Tips
提示
Changing the coordinate system of a data frame doesn't alter the coordinate system of the source data contained in it.
改变数据框的坐标系统不影响包含其中的源数据的坐标系统。
To see if your data source has a coordinate system defined, right-click the layer in the ArcMap table of contents and click Properties. Click the Source tab, then look in the Data Source box. You can also use ArcCatalog to see if your data has a coordinate system defined.
要看是否，您的数据源有一个被定义的坐标系统，单击ArcMap内容表中的那个层，再单击属性。单击“源”标签，再查看数据源框。你同样能用ArcCatolog来查看是否，您的数据源有一个被定义的坐标系统.
3.3 Finding out what map units your data is currently displayed with
找出你的数据当前显示于什么图距单位。
Right-click the data frame for which you want to determine the map units and click Properties.
右击你要确定图距单位的数据框再单击属性。
Click the General tab.
单击“一般”标签。
The current map units are shown.
当前图距单位显示。
Tip
提示
The data frame's display units, which were known as distance units in ArcView GIS 3 and ArcGIS 8, can be set independently of the map units. The display units are the units in which distances and coordinates will be displayed in ArcMap.
数据框的显示单位，在ArcView GIS 3和ArcGIS 8它被认为是距离单位，能独立于图距单位而设置。显示单位是ArcMap中距离和坐标被显示的单位。
3.4 Finding out the coordinate system of a layer's data source
指出某个层的数据源的坐标系统
Right-click a layer in the table of contents and click Properties.
右击内容表中的某个层，再单击属性。
Click the Source tab.
单击“源”标签
Scroll the information in the Data Source box. The coordinate system details are at the bottom of the list.
在数据源框中滚动信息，其坐标系统详细信息在列表底部。
3.5 Displaying data with a predefined coordinate system
以某个预定义的坐标系统显示数据。
Right-click the data frame for which you want to set the coordinate system and click Properties.
你要设置坐标系统的，右击数据框再单击属性
Click the Coordinate System tab.
单击坐标系统标签
Double-click Predefined.
双击预定义
Navigate through the folders until you find the coordinate system you want, then click it.
浏览整个文件夹直到找到你要的坐标系统，再单击它。
Click OK.
单击OK
All layers in the data frame will now be displayed with that coordinate system.
数据框中的所有层，现在将以这个坐标系统被显示。
Tip
提示
Changing the coordinate system of a data frame doesn't alter the coordinate system of the source data contained in it.
改变数据框的坐标系统不影响包含其中的源数据的坐标系统。
3.6 Modifying the parameters of a coordinate system
修改坐标系统的参数
Right-click the data frame for which you want to modify the coordinate system and click Properties.
你要修改坐标系统，右击数据框再单击属性。
Click the Coordinate System tab.
单击坐标系统标签
Click Modify.
单击修改
Adjust the coordinate system properties as appropriate and click OK.
恰当的调整坐标系统属性，再单击OK.
Click OK on the Data Frame Properties dialog box.
在数据框属性对话框中单击OK。
Tip
提示
Changing the coordinate system of a data frame doesn't alter the coordinate system of the source data contained in it.
改变数据框的坐标系统不影响包含其中的源数据的坐标系统。
3.7 Setting the units for reporting distance and displaying coordinates
设置单位来报告距离（｜即在测量地图的某些点的距离）和显示坐标。
Right-click the data frame and click Properties.
右击数据框再单击属性。
Click the General tab.
单击一般标签。
Click the Display drop-down arrow and click the appropriate units.
单击“显示”下拉箭头再单击适当的单位。
If this drop-down arrow is unavailable, the map units of your data frame are currently set to Unknown because no coordinate system has been specified for it.
如果这个下拉菜单不能获得（不可用），你的数据框的图距单位当前设置为Unknown，是因为没有为它设定一个坐标系统。
Click OK.
单击OK
Tips
提示
The data frame's display units, which were known as distance units in ArcView GIS 3.x and ArcInfo 8.x, can be set independently of the map units. The display units are used by the Measure tool, provide the default units used by scale bars, and are the units in which the map coordinate readout and the area and dimensions of graphics you draw are shown in the status bar.
数据框的显示单位，在ArcView GIS 3和ArcGIS 8它被认为是距离单位，能被独立于图距单位而设置。显示单位被测量工具使用、提供用于比例尺条的默认单位、是地图坐标和区域的读出（｜显示读数）和你制的图的尺寸的单位，显示在信息栏。
To set additional options for coordinate display in the status bar, click the Tools menu, then Options, and the Data View tab. There, you can set the number of decimal places shown (three is the default) and turn on thousand separators and zero padding. These settings are stored in the current map document (.mxd file) and apply to all the data frames in the map.
要为在信息栏中的坐标显示设置附加选项，单击“工具”菜单，再“设置”，再“数据查看”标签。在这里，你能设置小数（默认）和打开 thousand separators and zero padding。这些设置于当前地图文件（.mxd 文件）和应用于所有地图中的数据框。
When the display units are Degrees Minutes Seconds, the seconds are shown with three decimal places by default and respect what is specified on the Tools > Options > Data View tab.
当显示单位为度分秒，秒默认以3位小数显示，关于有哪些被设置，在Tools > Options > Data View 标签。
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Copyright ? Environmental Systems Research Institute, Inc.
unit of measure
测量单位
A standard quantity used for measurements such as length, area, and height.
一个标准的量用于没有如长度、区域和高度。