;
; TOBLER-FOUCAUT (1862)
; ====================
;
; Name:           Tobler-Foucaut(1862)
; Autor:          Fouaut 1862, publicated form Tobler 1973
; Quelle:         Tobler, W.; The Hyperelliptical and Other New Pseudo 
;                 Cylindrical Equal Area Map Projections.
;                 Journal of Geophys. Research, Vol. 78, No. 11, Apr. 10, 1973
;                 (Fig. 1)
; Direction:      Foreward (Direct) Transformation
;
; Scale and Zero-Longitude are inputable by user.
;

; (C) Rolf Böhm 2007

; Variables
; =========

	_name	Tobler-Foucaut_(1862)
	_var	phi		; Latude
	_var	lambda		; Longitude
	_var	sinphi
	_var 	cosphi	
	_var	scale		; Scale number (Note: 1000000, not 1/1000000)
	_var	lambda0		; Central Meridian
;
; x, y, x', y', Cx', Cy', °(, (°, pi, pi/2 etc. are pre-defined variables
;
; Init
; ====
;
	tstne	initial	077$
; Dialog
	pause	That~program~computes~a~foreward~transformation.¶
                ~It~must~use~a~direct~transformation~projection~engine. 
	input	scale	Scale~number
	input	lambda0	Central~longitude~in~degree
; Cilp~the~given~values
	clip	scale	1	1E12
	clip	lambda0	-180	180
; Programm is initialized
	mov	initial	1
077$:

;
; SIMD-Code
; =========

;
; Lambda/Phi
; ----------
;
	mov	lambda	x		; Receive the Longitude
	mov	phi	y		; Receive the Latitude
	sub	lambda	lambda0	
	cmod	lambda	-180	180

; Note: x, y have a double function: 
; - the general projection engine source co-ordinates (the Phi and Lambda in the formula),
; - also the map coordinates (will be written into the projection engine target co-ordinates x'/y')

;
; Degree into Arc
; ---------------
;
	mul	phi	°(		' The °( is a value in the RTA language!
	mul	lambda	°(
;
; Compute the Map Projection
; --------------------------
;
	mov	sinphi	phi
	sin	sinphi
	mov	cosphi	phi
	cos	cosphi
;
; x
;
	mov	r0	0.5
	mul	r0	cosphi
	add	r0	0.5
	mov	x	lambda
	mul	x	cosphi
	div	x	r0
;
; y
;
	mov	y	phi
	mul	y	0.5
	mul	sinphi	0.5
	add	y	sinphi		; not sinphi: sinphi/2
;
; Earth Radius, Scale division, Map centre
; ----------------------------------------
;
	mul	x	Rx'		; pre-defined by the projection engine
	div	x	scale		
	add	x	Cx'		; pre-defined ...	

	mul	y	Ry'
	div	y	scale
	add	y	Cy'
;
; Exit
; ----
;
	mov	x'	x
	mov	y'	y
	exit
	_end