cgutmzone.pro
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; docformat = 'rst'
;
; NAME:
; cgUTMZone
;
; PURPOSE:
;
; 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.
;******************************************************************************************;
; ;
; Copyright (c) 2012, by Fanning Software Consulting, Inc. All rights reserved. ;
; ;
; Redistribution and use in source and binary forms, with or without ;
; modification, are permitted provided that the following conditions are met: ;
; ;
; * Redistributions of source code must retain the above copyright ;
; notice, this list of conditions and the following disclaimer. ;
; * Redistributions in binary form must reproduce the above copyright ;
; notice, this list of conditions and the following disclaimer in the ;
; documentation and/or other materials provided with the distribution. ;
; * Neither the name of Fanning Software Consulting, Inc. nor the names of its ;
; contributors may be used to endorse or promote products derived from this ;
; software without specific prior written permission. ;
; ;
; THIS SOFTWARE IS PROVIDED BY FANNING SOFTWARE CONSULTING, INC. ''AS IS'' AND ANY ;
; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES ;
; OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT ;
; SHALL FANNING SOFTWARE CONSULTING, INC. BE LIABLE FOR ANY DIRECT, INDIRECT, ;
; INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED ;
; TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; ;
; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ;
; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ;
; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS ;
; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. ;
;******************************************************************************************;
;
;+
; 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.
;-
FUNCTION cgUTMZone, longitude, latitude, FORMAL=formal
Compile_Opt idl2
Catch, theError
IF theError NE 0 THEN BEGIN
Catch, /CANCEL
void = cgErrorMsg()
RETURN, 0
ENDIF
; Must pass a lon/lat pair of values.
IF N_Params() NE 2 THEN Message, "Must past longitude and latitude as input parameters."
; Set up the latitudes.
latnotes = ['AB', 'C','D','E','F','G','H','J','K','L','M','N','P','Q','R','S','T','U','V','W','X','YZ' ]
latbands = [-90, cgScaleVector(Findgen(21), -80, 80), 90] ; Zones every 8 degrees, except for poles.
latbands[20] = 84 ; Last zone extended 4 degrees.
; Find the latitude band.
latbandIndex = 0 > Value_Locate(latbands, latitude) < (N_Elements(latnotes)-1)
latBand = latnotes[latbandIndex]
IF latBand EQ 'AB' THEN BEGIN
IF (longitude LT 0) THEN latBand = 'A' ELSE latBand = 'B'
ENDIF
IF latBand EQ 'YZ' THEN BEGIN
IF (longitude LT 0) THEN latBand = 'X' ELSE latBand = 'Z'
ENDIF
; Get longitude in the range -180 to 180.
IF longitude GT 180 THEN longitude = longitude - (Long(longitude)/180)*360.0
; Find the zone, with exceptions.
lonbands = cgScaleVector(Findgen(61),-180, 180)
IF latBand EQ 'V' THEN lonbands[32] = 9.00
; Find the zone.
zone = ((Value_Locate(lonbands, longitude) + 1))[0]
; This program does NOT correct for exceptions in the Svalbard region in the X latitude band.
; Warn the user.
IF latBand EQ 'X' && ((zone GE 32) && (zone LE 37)) THEN $
Message, 'UTM zone designations for the Svalbard region are not correct.', /Informational
; The formal designation.
formal = StrTrim(zone,2) + latband
; For IDL's purpose, southern hemisphere is indicated by negative value.
IF (latBand LT 'N') THEN zone = -zone
RETURN, zone
END