Start(): convention for lat/lon range

In Start(), to assign the region you want to load, you put the numbers (lon.min, lon,max, lat.min, and lat.max) in parameters latitude and longitude. For now, the range of the numbers is unclear, and it rarely returns error and warning when strange range is assigned (e.g., lon > 360).

The regulation should be found and written in the document. Also some warnings should be added in the code, so users can have a clear picture that what lat/lon range they actually load.