这是android开发的谷歌地图，可以选择地图上任意一点再计算与指定经纬度的距离。-This is a Google Maps android development, you can select and then calculate the distance between any point on the map with the specified latitude and longitude.

通过输入大地经纬度，中央子午线，计算出改点子午线收敛角(The convergent angle of meridional line is calculated by entering the longitude and latitude of the earth and the central meridian.)