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### MAP_VECTOR__DEFINE

MAP_VECTOR__DEFINE

## Name

MAP_VECTOR__DEFINE

## Purpose

This object is a wrapper for the CAT_ARROW routine in IDL. It provides a simple
way to draw arrows or vectors on images which use a MAPCOORD object to set up the map
projection space. A map coordinate space must be in effect at the time the
Draw method of this object is used.

## Author

FANNING SOFTWARE CONSULTING
David Fanning, Ph.D.
1645 Sheely Drive
Fort Collins, CO 80526 USA
Phone: 970-221-0438
E-mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com

Graphics

## Calling Sequence

mapCoord = Obj_New('MapCoord', 111, CENTER_LON=0, CENTER_LAT=90)
vectorObject = Obj_New('Map_Vector', lon, lat, u, v, mapCoord)
vectorObject -> Draw
ObjDestroy, mapCoord, vectorObject

## Auguments

lon: A vector (or scalar) containing the longitude location of the (x0,y0) end of a vector.

lat: A vector (or scalar) containing the latitude location of the (x0,y0) end of a vector.
u: A vector (or scalar) containing the horizontal (X or longitude) component of the vector.
v: A vector (or scalar) containing the vertical (Y or latitude) component of the vector.
mapCoordObj: A map coordinate object which can return a map structure for converting coordinates
to/from lat/lon coordinates to XY coordinates. Typically, a MAPCOORD object. An
alternative way of specifying a map coordinate object is to use the MAP_OBJECT
keyword. But don't do both. Note, this object is *not* destroyed when the MAP_VECTOR
object is destroyed. You are responsible for destroying the map coordinate object.
A map coordinate object is REQUIRED. So, if you don't specify this parameter, use the
MAP_OBJECT keyword to pass this object into the program.

## Keywords

All of the following INIT keywords can be set and obtained using the SETPROPERTY and GETPROPERTY methods.

CLIP: The coordinates of a rectangle used to clip the graphics output.
The rectangle is specified as a vector of the form [X0, Y0, X1, Y1],
giving coordinates of the lower left and upper right corners,
respectively. The default clipping rectangle is the plot window set
up by the MAPCOORD object.

COLOR: The name of the color to draw the arrow or vector in. Default: "white".
HSIZE: The value of this keyword sets the length of the arrowhead. See the documenation
for the ARROW command for further explanation. Default is -0.35.
LENGTH: The U and V vectors are mutiplied by LENGTH before they are used
to calculate the (x1,y1) endpoint of the vector. By default, the length is set
to 1/100th of the XRANGE of the MapCoord object. This means that the maximum
length of a vector will be approximately LENGTH * SQRT(2).

LINESTYLE: Set this keyword to the type of linestyle desired. See Graphics Keywords in
the on-line help for additional information. Default is 0, solid line.

MAP_OBJECT: A MAPCOORD object or equivalent which had the ability to provide a map
structure with a GetMapStructure method. Don't use this keyword if you have
passed a map coordinate object as a positional parameter.

NOCLIP: Set this keyword to surpress clipping of the arrow. Set to 0 by default.
PARENT: An object reference to an object that will be the parent of this object.

SOLID: Set this keyword to make a solid arrow, using polygon fills.

THICK: The thickness of the lines. Set to 1.0 by default.

UVCOORDS: Set this keyword if the LON and LAT arrays are specified in UV coordinates, rather than
longitude and latitude coordinates.

## Dependencies

The following programs (at least) are required from the Coyote Library:
http://www.idlcoyote.com/programs/error_message.pro
http://www.idlcoyote.com/programs/cgcolor.pro
http://www.idlcoyote.com/programs/cgsymcat.pro

## Modification History

Written by David W. Fanning, 14 June 2010.

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