coyote: CGKML_LOOKAT__DEFINE

Description
This program implements the KML abstract LookAt class. For 
reference, see  the `Google KML Reference Documentation `.
A LookAt object extends a KML Object. The purpose of this object is to allow
Google Earth to "fly to" a particular location.
Categories
Graphics, FileIO
Examples
See the `cgKML_File` object for examples of how to create a KML file.
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
Change History::
   Written, 31 December 2012 by David W. Fanning.
Copyright
Copyright (c) 2012, Fanning Software Consulting, Inc.
e purpose of this method is to establish a KML LookAt object class. For reference, see
tps://developers.google.com/kml/documentation/kmlreference#lookat.
Keywords
altitudemode: in, optional, type=string, default="relativeToGround"
     The mode of the altitude. Possible values are: "clampToGround", "relativeToGround"
     and "absolute".
heading: in, optional, type=float, default=0.0
     The angle of the view. Valid values 0 to 360.
height: in, optional, type=double, default=500.0
     The altitude (in km) of the eye with respect to the lat/lon point of the eye.
     Called "altitude" in the KML documentation, but called "height" here to differentiate
     keyword from "altitudeMode".  Positive values in kilometers.
latitude: in, optional, type=float, default=0.0
     The input latitude where the eye should be located. Valid values -90 to 90.
longitude: in, optional, type=float, default=0.0 
     The input longitude where the eye should be located. Valid values -180 to 180.
tilt: in, optional, type=float, default=0.0
     The tilt angle of the eye. Valid values 0 to 90.
 _ref_extra: in, optional
     Any keywords appropriate for superclass objects may be passed into the program.
he purpose of this method is to destroy anything we created that may leak
emory or need to be released from use.
he cgKML_LookAt class definition module. This is a class that allows the
oogle Earth application to "fly to" the position indicated.
Params
class: out, optional, type=structure
    The class definition returned as a structure variable. Occassionally useful.