Bounding Box

osmctools, osmium都会用到

A bounding box (usually shortened to bbox) is an area defined by two longitudes and two latitudes, where:

• Latitude is a decimal number between -90.0 and 90.0.
• Longitude is a decimal number between -180.0 and 180.0.
  They usually follow the standard format of:

  bbox = left,bottom,right,top
  bbox = min Longitude , min Latitude , max Longitude , max Latitude 

  即左下右上的经纬度