今天开始学习第三课，下面是课程结束之后老师的总结。
Finding data is its own challenge that you will always be trying to master.
第一节是重复一遍如何找到数据的，具体方法在第一堂课的指南中提到。
You now know how to use data frames, create basic layout views, andexport maps as PDFs.
这一小节有一些重点：
layer property：层的属性，其中包含coordinate system
data frame的设置：借助view——layout view调出，其中可以添加title并且能通过pdf导出
We covered navigation in layout view and adding legends, scale bars,north arrows, and text store map layouts.One thing to remember is that if you want to change the properties oroptions of something in layout view, that's accessed by double clicking on it.See you in the next activity.
这一小节主要讲了如何修正layout view，以及如何增加图例、比例尺以及指北符号。
