8、五分钟构建一张图

三维地理信息系统一般由基础地图、三维地形数据、专题数据等几个要素组成，通常也称之为一张图。

借助CesiumEarth快速加载图层的能力，可在短时间内构建一套完整的一张图。

构建步骤主要分以下三个步骤：

第一步：添加基础地图资源

互联网提供了许多免费使用的地图资源，文档中介绍了几种常见的资源地址，点击查看免费资源详情

本文选用天地图卫星影像、天地图注记两个图层

1、添加天地图卫星影像

点击添加图层，选择二维切片数据，选择自定义格式
输入Url参数
http://{s}.tianditu.com/DataServer?T=img_w&X={x}&Y={y}&L={z}&tk=0f84da9fd48038ea3bd8de15ff9fb4c2
输入前缀：t0,t1,t2,t3,t4,t5,t6,t7
点击确认后卫星影像添加完毕

此时效果如下：

2、添加天地图注记

点击添加图层，选择二维切片数据，选择自定义格式
输入Url参数
http://{s}.tianditu.com/DataServer?T=cia_w&X={x}&Y={y}&L={z}&tk=0f84da9fd48038ea3bd8de15ff9fb4c2
选中注记图选项
输入前缀：t0,t1,t2,t3,t4,t5,t6,t7
点击确认后注记图层添加完毕

此时效果如下：

第二步：添加三维地形

三维地形也就是高程数据，可使地图呈现三维效果，CesiumEarth自带Cesium Ion三维地形模块，直接添加即可加载

点击添加图层，选择地形数据
选择默认格式
Token参数中输入Cesium Ion申请的Token值 eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJqdGkiOiJjMWYwNDIxZS05N2NhLTQyY2UtYWEzMi01NzFiYzA5ZDVjNjIiLCJpZCI6NDcyNDQsImlhdCI6MTYxNzAwODE0Nn0.0VGcsvaBuAbCFp1AdfYQjFwjZF4Y7OyG8MNy3YKIsDI
点击确认后三维地形数据添加完毕

此时效果如下：

第三步：添加专题数据

专题数据是一张图元素的主要内容，可展现各种行业各种场景的要素数据。

本文以武汉大学东湖景点为例，导入的数据是提前准备好的东湖景点矢量点数据（geojson格式）。

1、添加东湖景点矢量数据

点击添加图层，选择矢量数据
数据来源选择本地数据
点击打开文件，选中geojson
点击确认后东湖景点添加完毕

此时效果如下：

2、修改景点显示样式

默认添加后的点数据比较简单，为了表达景点专题图的风格，需要对样式进行调整

选中东湖景点，点击图层设置，修改参数如下
pointShow = 0
bubbleShow = 1
bubbleImage = http://cesiumearth.com/resources/bubbles/Bub6.png (此处可以替换成自己喜欢的图标链接)
bubbleScale = 0.3
labelShow = 1
labelField = 名称 （geojson中的字段名称，支持中文字段）
labelPixelOffset = 0,-50
labelFillColor = #0088FF

此时效果如下：

第四步：总结

到此为止，一张图要素中的基础地图资源、高程数据、专题数据已经添加完毕。

本文中专题数据只举例了矢量点及其样式的修改，若涉及到更多专题数据，如线、面等其他矢量数据，也可在后续进行添加，以丰富一张图的数据内容。

以下为本例中的图层配置数据，可通过添加图层、配置数据功能快速添加：

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