MapServer Tutorial——MapServer7.2.1教程学习——第一节用例实践：Example1.6 Defining Projections and Extents

MapServer Tutorial——MapServer7.2.1教程学习——第一节用例实践：Example1.6 Defining Projections and Extents

一、前言

　　当在mapfile文件中定义PROJECTION对象时，MapServer将图层和投影信息传递给proj.4库执行重投影。详情请看：https://proj4.org/。

　　有数以千计的地理参考系统。为了将数据集与不同地理参考系统结合到地图中，必须将数据集转换（投影）到地图中选定的地理参考系统。

　　PROJECTION在MapServe中，则是制定使用哪种地理残念考系统。（同属理解，就是你当前的数据是使用哪种坐标信息。）

　　既然PROJECTION是用来指定数据所使用的坐标系信息，那么，它出现的位置就应该在需要使用显示数据的地方。

　　第一个就是mapfile的MAP标签里面，用来定义输出坐标系；第二个位置就是LAYER标签里面，定义输入坐标系。

二、在MapServer中使用投影（Projections with MapServer）

　　如果要使用PROJECTION，你必须在mapfile中MAP标签下面定义一个输出PROJECTION。然后每个LAYER里面必须定义输入坐标系。（注意是必须定义）

　　PROJECTION对象是有一系列的PROJ.4库关键字构成。要么直接用关键书写；要么引用EPSG文件。格式如下。（EPSG详见：https://www.mapserver.org/glossary.html#term-epsg）

　　EPSG代码是与坐标系定义相关联的数字代码。如：EPSG:4326（EPSG:4326就是WGS84）

　　ESPG相关资料：

• • 官网：http://www.epsg.org/
  • ESPG数据资料：http://spatialreference.org/

#直接使用PROJ.4库关键字构建PROJECTION

PROJECTION
  "proj=utm"
  "ellps=GRS80"
  "datum=NAD83"
  "zone=15"
  "units=m"
  "north"
  "no_defs"
END

#通过EPSG构建PROJECTION

PROJECTION
   "init=epsg:26915"
END

三、创建Example1.6站点

　　在cmd中输入：cd /d E:\SvnWorkspace\LY_WEB_GIS\branches\Documents\ms4w-mapserver-for-wimdows\release-1911-x64-gdal-2-3-3-mapserver-7-2-1\apps

　　在cmd中输入：md Example1.6

　　在cmd中输入：cd Example1.6

　　在cmd中输入：md data

　　在cmd中输入：md fonts

　　在cmd中输入：md symbols

　　在cmd中输入：md logs

　　在cmd中输入：cd.>web.config

　　在cmd中输入：cd.>example1_6.map

　　在cmd中输入：cd data

　　在cmd中输入：md raster

　　将 app/tutorial/fonts 文件夹中的所有文件拷贝到 apps/Example1.6/fonts 文件夹中

　　将 app/tutorial/symbols 文件夹中的 symbols35.sym 文件拷贝到 apps/Example1.6/symbols 文件夹中

　　将 app/tutorial/data 文件夹中的 states_ugl.dbf、states_ugl.shp、states_ugl.shx 文件拷贝到 apps/Example1.6/data 文件夹中

　　将 app/tutorial/data/raster 中的 mod09a12003161_ugl_ll_8bit.tif 文件拷贝到 apps/Example1.6/data/raster 文件夹中

　　修改 web.config 文件如下：

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.webServer>
        <handlers>
            <add name="MapServerFastCgi" path="*" verb="*" type="" modules="FastCgiModule" 
　　　　　　　　　　scriptProcessor="E:\SvnWorkspace\LY_WEB_GIS\branches\Documents\ms4w-mapserver-for-wimdows\release-1911-x64-gdal-2-3-3-mapserver-7-2-1\bin\mapserv.exe" 
　　　　　　　　　　resourceType="Unspecified" requireAccess="Script" allowPathInfo="false" preCondition=""  />
        </handlers>
        <caching enabled="true" enableKernelCache="true" />
    </system.webServer>
</configuration>

　　修改MapFIle（example1_6.map）文件如下：

# The annotated map file (sort of)
# Created by Pericles S. Nacionales for the MapServer tutorial
# 20050408
#
# MapServer map file uses the pound sign (#) to denote the start of a line
# comment--each line that needs to be commented has to be prepended with a "#".
#
# Map files begin with MAP keyword to signify the start of the map object.
# Well, the entire map file is THE map object.  Enclosed between MAP and END
# at the very bottom of this map file, are keyword/value pairs and other
# objects.
MAP
  #IMAGETYPE      PNG24
  IMAGETYPE      PNG
  #EXTENT       -97.238976 41.619778 -82.122902 49.385620                       # WGS84            经纬度坐标数据
  #EXTENT        201621.496941 -294488.285333 1425518.020722 498254.511514      # LAEA 原始官网mapfile中的数据
  EXTENT         230147.11 -371641.81 1285308.08 632638.93                      # LAEA 自己通过命令计算的坐标数据
  #EXTENT        -97.5 41.619778 -82.122902 49.38562                            # Geographic
  SIZE           400 300
  SHAPEPATH      "./data"
  SYMBOLSET      "./symbols/symbols35.sym"
  FONTSET        "./fonts/fonts.list"

  # The projection object is typically used within the map and the layer
  # objects. You only define it once within the map object and this definition
  # becomes your output projection--MapServer will render your maps in this
  # projection.  You also use the projection object within the layer object to
  # define your input projection.  Your layers can be in different
  # projections--MapServer will reproject them into your output projection.
  # If no projection is defined within the layer object, MapServer assumes
  # your input projection is the same as your output projection.  This is not
  # a required object unless you're creating a map file that supports one of
  # the OGC interoperability web services specifications (WMS/WFS/WCS).
  #
  # This is the output PROJECTION definition ------
  PROJECTION
    # Projection parameters can be defined in two ways...
    # This is the traditional PROJ.4 definition of Lambert Azimuthal Equal-Area
    # projection for the Continental U.S.
      "proj=laea"
      "ellps=clrk66"
      "lat_0=45"
      "lon_0=-100"

    # Alternatively, you can specify an EPSG code.
    # This is the EPSG code for Lambert Azimuthal Equal-Area
    # projection for the U.S.
    #
    # "init=epsg:2163"
  END # End of the output Projection definition ---

  # Layer objects are defined beneath the map object.  You need at least one
  # layer defined in your map file before you can display a map...  You can
  # define as many layers as you'd like although a limit is typically hard-coded
  # in map.h in the MapServer source.  The default limit is set at 100.  You'd
  # have to have a very specialized application to need more than 100 layers in
  # your application.
  #
  # Start of LAYER DEFINITIONS ---------------------------------------------
  LAYER # States polygon layer begins here
    NAME         states_polygon
    DATA         states_ugl
    STATUS       OFF
    TYPE         POLYGON

    # Here's an example of the input projection definition.
    # EPSG:4326 is code for geographic (latlong) projection
    # using the WGS84 datum.
    #
    # PROJECTION objects within the LAYER object define the input
    # projection--this is the native projection of your data.
    PROJECTION
      "init=epsg:4326"
    END

    # CLASSITEM defines the non-spatial attribute that you will be using to
    # separate a layer into classes.  This attribute will be in the DBF file
    # of your shapefile (it will be different for each data format).  In this
    # example the shapefile states_ugl has an associated database
    # (states_ugl.dbf) that contains an attribute called "CLASS".  You will be
    # using two values in the CLASS attribute to separate the classes (also
    # called themes) used in this layer--land and water.  CLASSITEM is used in
    # association with the EXPRESSION parameter in the CLASS object.  See below.
    CLASSITEM    "CLASS"

    # The class object is defined within the layer object.  You can define as
    # many classes as you need (well, there are limits as with layers, but it's
    # senseless to define more than ten on a "normal" layer.  There are
    # situations, however, where you might have to do it.)
    CLASS
      NAME 'States'
      EXPRESSION 'land'

      # There are styles in a class, just like there are classes in a layer,
      # just like there are layers in a map.  You can define multiple styles in
      # a class just as you can define multiple classes in a layer and multiple
      # layers in a map.
      STYLE
        COLOR      232 232 232
      END
    END
  END # States polygon layer ends here

  # In addition to vector data (shapefiles are vector data), MapServer supports
  # a host of raster formats.  In GIS world, one of the most common raster
  # formats is GeoTIFF, a TIFF image with geospatial headers.  MapServer also
  # supports JPEG, PNG, GIF, and other common formats.  Other raster formats
  # supported by MapServer include ESRI Arc/Info grid, HDF and HDF-EOS, NetCDF,
  # Generic raster binaries, OGC Web Map Service (WMS) layers, etc.  Pretty much
  # any raster format you can think of is probably supported, thanks to the
  # impressive Geospatial Data Abstraction Library (GDAL, pronounced "GOODALL"
  # or GOODLE?).  More information on GDAL is available at http://www.gdal.org.
  #
  # MapServer 4.x can read and display bitmapped (like GIFs), RGB/A (true
  # color), and multispectral (images with more than 3 bands, like raw LandSat
  # images) rasters.
  LAYER # MODIS raster layer begins here
    NAME         modis
    DATA         "raster/mod09a12003161_ugl_ll_8bit.tif"
    STATUS       OFF
    TYPE         RASTER
    PROCESSING   "BANDS=1,2,3"
    OFFSITE      71 74 65

    PROJECTION
      "init=epsg:4326"
    END
  END # MODIS raster layer ends here

  LAYER # States line layer begins here
    NAME         states_line
    DATA         states_ugl
    STATUS       OFF
    TYPE         LINE

    PROJECTION
      "init=epsg:4326"
    END

    CLASSITEM    "CLASS"
    CLASS
      NAME       'State Boundary'
      EXPRESSION 'land'
      STYLE
        SYMBOL     'line5'
        COLOR      64 64 64
        SIZE       1
      END
    END
  END # States line layer ends here

  LAYER # States label layer begins here
    NAME         states_label
    DATA         states_ugl
    STATUS       OFF
    TYPE         POLYGON

    PROJECTION
      "init=epsg:4326"
    END

    CLASSITEM    "CLASS"

    # Just like CLASSITEM, LABELITEM defines the database attribute that you
    # will be using to draw labels.  In this case, the values of the attribute
    # "STATE" will be used to label the states polygons.
    LABELITEM    "STATE"
    CLASS
      EXPRESSION 'land'
      STYLE
        COLOR      -1 -1 -1
      END

      # There can be labels in a class, just like there are classes in a layer,
      # just like there are layers in a map.  You can define multiple labels in
      # a class just as you can define multiple classes in a layer and multiple
      # layers in a map.
      # MapServer has a very flexible labeling system.  With that flexibility
      # comes complexity, specially when using truetype fonts.  Please read
      # through the LABEL section of the MapServer map file documentation at
      # http://www.mapserver.org/mapfile for more information.
      LABEL
        COLOR 132 31 31
        #SHADOWCOLOR 218 218 218
        #SHADOWSIZE 2 2
        TYPE TRUETYPE
        FONT arial-bold
        SIZE 12
        ANTIALIAS TRUE
        POSITION CL
        PARTIALS FALSE
        MINDISTANCE 300
        BUFFER 4
      END # end of label
    END # end of class
  END # States label layer ends here
  # End of LAYER DEFINITIONS -------------------------------
  DEBUG 5
  CONFIG "MS_ERRORFILE" "logs\ms.log"
END # All map files must come to an end just as all other things must come to...

　　在 IIS 中创建站点 Example1.6，端口为8016，应用程序池为 Example1.6

　　设置应用程序池对 apps/Example1.6/logs 文件夹的读写权限

　　在cmd中输入：icacls "E:\SvnWorkspace\LY_WEB_GIS\branches\Documents\ms4w-mapserver-for-wimdows\release-1911-x64-gdal-2-3-3-mapserver-7-2-1\apps\Example1.6\logs" /grant "IIS AppPool\Example1.6":(OI)(CI)RW

　　在浏览器中打开：http://localhost:8016/mapserv?map=../apps/Example1.6/example1_6.map&layer=states_polygon&layer=modis&layer=states_line&layer=states_label&mode=map

 四、EXTENT的改变

　　查看mapfile（example1_6.map）文件后，首先，你会发现最明显的改变是 MAP 标签下面的 EXTENT 标签的数据。

　　EXTENT 表示当前数据文件的显示范围。现在的显示方为值如下：

EXTENT       201621.496941 -294488.285333 1425518.020722 498254.511514

#Example1.5 中是：EXTENT         -97.238976 41.619778 -82.122902 49.385620

　　为什么会发生这样的改变呢，应为我们修改了MapServer 的输出坐标系，即添加了 PROJECTION 对象。

　　EXTENT对象的输出单位必须与 MapServer 中的输出坐标系一致。

　　先前的坐标系是经纬度。现在 PROJECTION  设置为：

  # The projection object is typically used within the map and the layer
  # objects. You only define it once within the map object and this definition
  # becomes your output projection--MapServer will render your maps in this
  # projection.  You also use the projection object within the layer object to
  # define your input projection.  Your layers can be in different
  # projections--MapServer will reproject them into your output projection.
  # If no projection is defined within the layer object, MapServer assumes
  # your input projection is the same as your output projection.  This is not
  # a required object unless you're creating a map file that supports one of
  # the OGC interoperability web services specifications (WMS/WFS/WCS).
  #
  # This is the output PROJECTION definition ------
  PROJECTION
    # Projection parameters can be defined in two ways...
    # This is the traditional PROJ.4 definition of Lambert Azimuthal Equal-Area
    # projection for the Continental U.S.
      "proj=laea"
      "ellps=clrk66"
      "lat_0=45"
      "lon_0=-100"

    # Alternatively, you can specify an EPSG code.
    # This is the EPSG code for Lambert Azimuthal Equal-Area
    # projection for the U.S.
    #
    # "init=epsg:2163"
  END # End of the output Projection definition ---

　　现在的 PROJECTION 设置为：Lambert Azimuthal Equal-Area，其单位为米，所以我们现在的范围 EXTENT 也要设置为米。

　　可以通过 ArcView、PROJ4 的 cs2cs 或其他GIS包做转换。下面的命令可用于重新投影原始范围值：

#第一步
#在cmd中输入：cd /d E:\SvnWorkspace\LY_WEB_GIS\branches\Documents\ms4w-mapserver-for-wimdows\release-1911-x64-gdal-2-3-3-mapserver-7-2-1\apps\tutorial\data
#在cmd中输入：ogrinfo -ro -al -so states_ugl.shp
#获取到states_ugl.shp 的范围信息：Extent: (-97.238976, 41.619778) - (-82.122902, 49.385620)。 Extent的格式为：<Lower Left X> <Lower Left Y> <Upper Right X> <Upper Right Y>

#然后在cmd中输入下面的命令，回车

cs2cs +proj=latlong +datum=WGS84 +to +proj=laea +ellps=clrk66 +lat_0=45 +lon_0=-100

#执行当前计算转换，是在数据命令后，在输出原始范围的西南坐标值。即左下角坐标值，用空格分割开

-97.238976 41.619778 

#回车后得到三个值，分别为：西南方向 X、Y、单位精度，其中第三个参数可以忽略。

230147.11       -371641.81 0.00

#接着再输入东北方向坐标参数

-82.122902 49.385620

#得到东北方向的转换输出范围：

1285308.08      632638.93 0.00

#所以转换后的EXTENT值为：

EXTENT 230147.11 -371641.81 1285308.08 632638.93

#转换完毕

#但是原始官网mapfile文件中给出的 EXTENT 值与计算值不符合。这是为什么呢？

EXTENT 201621.496941 -294488.285333 1425518.020722 498254.511514      # LAEA 原始官网mapfile中的数据

#因为地图在数据范围中并不居中，你可以适当的增加其范围，加以调整使其居中。官网案例是通过ArcView获取的。

　　当使用自己计算的范围时和官网通过ArcView修改后的范围，其显示为分别如下：

    

　　对比会发现，官网给定的做了相关边距接线的调整。

五、后记

　　在做本样例中，对MapServer又有了新的认识：

• • 可以自定义投影坐标系的输出类型。
  • PROJECTION中是如何通过PROJ4关键词参数定义输出坐标系的。
  • PROJECTION是如何EPSG文件。
  • EPSG文件到底是个什么东西：http://www.epsg.org/
  • EPSG文件也可以自定义其目录位置。
  • PROJ4中cs2cs命令的使用

MAP
  CONFIG "PROJ_LIB" "/usr/share/proj/"  #UNIX的绝对路径，如果是未定义，则按照安装MapServer中的 E:\SvnWorkspace\LY_WEB_GIS\branches\Documents\ms4w-mapserver-for-wimdows\release-1911-x64-gdal-2-3-3-mapserver-7-2-1\bin\proj\SHARE 路径查找（个人理解）
  PROJECTION
    "init=epsg:3857"
  END # PROJECTION
  ...

　　　　后面还想写一篇关于关于PROJ4坐标转换的文章。一部一部学习。