绘制漂亮的中学操场轮廓，生成带经纬度数据

下图是一个中学的建筑、操场、绿地polygon数据，这些数据都是基于geobuilding绘制的，这里介绍下操场的绘制方法。

操场可以理解为2个半圆加一个长方形合并，我们使用参考线工具来绘制, 通过【左转】、【右转】调整地图旋转，确保操场水平线和水平刻度重合。拖动参考球(绿色)到合适的矩形位置。拖动到合适位置后，【锁定参考线】。如下图

下面开始绘制左边的圆，步骤

拖动参考球410*410,正方形框，1点击【绘制图形】按钮，2、然后选中刚绘制的矩形，输入正40边，点击【框内正】按钮

选中这个圆形，点击参考线工具【左右对称复制】生成右侧圆形

下面我们需要中间的长方形，还要确保长方形的四个顶点正好在圆的上下点上。拖动参考线十字距离左侧205px；右侧参考球到圆的上下点。拖动好了以后，点击【创建图形】得到矩形

按着shift键，同时选择2个圆形和中间的矩形，点击【面合并】按钮

合并后隐藏参考线，如下图，我们得到了漂亮的操场轮廓。

本教程地图信息，打开geobuilding，在右侧地图信息粘贴可直达该位置。 {"zoom":17.06123136912676,"center":[116.14629597404104,39.72563348924925],"pitch":0} 绘制的跑道geojson数据 {"id":"b34dcb8a432a1a216310cf80d2ccc14a","type":"Feature","properties":{"floor":1,"name":"","id":"b34dcb8a432a1a216310cf80d2ccc14a"},"geometry":{"coordinates":[[[116.14557110400716,39.72538878432343],[116.14557129756217,39.725388783946336],[116.1455771175672,39.725330004406715],[116.14559539120063,39.72527080266312],[116.14562548117965,39.72521452836315],[116.14566664659083,39.72516256717577],[116.1457178738039,39.72511619856854],[116.14577790143557,39.72507656430338],[116.14584525140629,39.72504464031917],[116.14591826533592,39.72502121270233],[116.14599514537991,39.725006858326196],[116.1460739984962,39.72500193064994],[116.146152883058,39.725006551011006],[116.1462298566683,39.72502060563855],[116.14630302397796,39.725043748456045],[116.14637058336751,39.725075409601374],[116.1464308713002,39.72511480946042],[116.14648240328614,39.72516097786615],[116.14652391043694,39.72521277798688],[116.14655437071013,39.72526893432095],[116.14657303407103,39.72532806410271],[116.1465792411826,39.72538682021288],[116.14657943473634,39.72538681983579],[116.1465820014106,39.72616612222848],[116.14658180785683,39.72616612260556],[116.14658200764103,39.72616801372865],[116.14657600031313,39.72622868443011],[116.14655772668124,39.726287885350644],[116.14652763670068,39.726344158774566],[116.14648647129104,39.72639611907155],[116.14643524407637,39.72644248681803],[116.14637521644465,39.72648212029736],[116.14630786647405,39.72651404361605],[116.1462348525443,39.72653747072627],[116.1461579725003,39.7265518247838],[116.14607911938566,39.72655675234927],[116.14600023482228,39.72655213209211],[116.14592326121198,39.7265380777761],[116.14585009390225,39.726514935460756],[116.1457825345127,39.72648327497646],[116.14572224658167,39.726443875899406],[116.14567071459578,39.72639770835198],[116.14562920744333,39.726345909121505],[116.14559874717179,39.72628975366521],[116.14558008380925,39.72623062470754],[116.14557367691185,39.72616997819466],[116.14557386423661,39.7261680863168],[116.14557367067982,39.72616808669389],[116.14557110400716,39.72538878432343]]],"type":"Polygon"}}

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