coyote: CGUTMZONE

Description
This function returns the correct UTM zone for UTM map projections, given a longitude
and latitude value. Southern hemisphere zones are indicated by a negative value.
Categories
Utility
Params
longitude: in, required, type=float
   The requested longitude value east of the central meridian.
latitude: in, required, type=float
   The requested latitude value in the range -90 to 90.
Keywords
formal: out, optional, type=string
  The formal UTM zone designation, with the zone number and band letter combined. For example, "32M".
Examples
For example, to find the UTM zone for London, England::
   Print, cgUTMZone(-1.062, 51.5171, FORMAL=strDesignation)
       30
   Print, strDesignation
       30U
Author
FANNING SOFTWARE CONSULTING::
   David W. Fanning 
   1645 Sheely Drive
   Fort Collins, CO 80526 USA
   Phone: 970-221-0438
   E-mail: david@idlcoyote.com
   Coyote's Guide to IDL Programming: http://www.idlcoyote.com
History
Written, 8 August 2012.
Modified to assure the UTM band index is always in range for polar map projections. 22 Sept 2012. DWF.
Copyright
Copyright (c) 2012, Fanning Software Consulting, Inc.