;+
; NAME:
;	ThomsonSetupLOS
; PURPOSE:
;	Sets up common block used by href=ThomsonLOSDensity= to
;	calculate electron density at specified locations
; CATEGORY:
;	Physics: Thomson scattering
; CALLING SEQUENCE:
	PRO ThomsonSetupLOS, PosIn, DirIn, density=densityIn
; INPUTS:
;	Pos			array[3,n]; type: float
;					heliocentric location(s) of observer:
;					(longitude and latitude in radians;
;					and heliocentric distance in solar radii)
;	Dir			array[2,m]; type: float
;					topocentric longitude and latitude of
;					lines of sight relative to Sun-observer
;					direction (in radians)
;
; OPTIONAL INPUT PARAMETERS:
;	density=density
;			scalar; type: string; default: undefined
;				name of function to be called to calculate
;				the electron density. This function takes
;				a single argument:
;				R	array[3,n]; type: float
;						heliocentric locations where density is
;						to be evaluated, usually
;						ecliptic longitude and latitude (radians)
;						and heliocentric distance (solar radii)
; OUTPUTS:
;	(stored in common block)
; INCLUDE:
	@compile_opt.pro		; On error, return to caller
	@thomson_common.pro 	; Dummy comment
; CALLS:
;	boost, destroyvar, IsType
; SEE ALSO:
;	ThomsonLOSDensity
; PROCEDURE:
;	The input is stored in common block thomson_common.
;	ThomsonLOSDensity uses these together with an input
;	argument S (1-dim array[k]) specifying distances
;	along the line of sight, and calculates densities
;	at locations Loc[k,m,n] (k locations on m lines
;	of sight at n locations.
; MODIFICATION HISTORY:
;	JAN-1998, Paul Hick (UCSD)
;-

Pos_ = PosIn
Dir_ = DirIn

boost, Dir_, plus=1 ; [2,nlos] -> [3,nlos]

CASE IsType(densityIn, /defined) OF
0: destroyvar, density
1: density = densityIn[0]
ENDCASE

RETURN  &  END