point map symbol japanese triangulation Japanese Map Symbol Triangulation Point clip art vector graphic can be downloaded for free 日语 符号 三角剖分 日本地图符号三角点
Demonstrates how GPS works using trilateration. Each satellite is at the center of a sphere and where they all intersect is the position of the GPS receiver 全球导航卫星系统 全球定位系统 gps satellites GPS 卫星-三边测量法