models/johnpye/spherical.a4c

REQUIRE "atoms.a4l";

(* 
	simple model for some spherical geometry: latitude and longitude angles
	subtended by North-South distance (dy) and East-West distance (dx) on
	a sphere of given radius, given the local latutide (phi) and longitude
	(theta).

	The 'on load' configuration of this model gives the dimensions N-S and E-W
	corresponding to a 1 deg-lat x 1 deg-long square in Sydney.

	TODO:
	More useful calculators such as distance between two points,
	area of trianges, etc.
*)
MODEL spherical;
	dx, dy IS_A delta_distance; (* E-W, N-S *)
	R IS_A distance;

	phi, theta IS_A angle; (* latitude, longitude *)
	dphi, dtheta IS_A angle;

	dx = R*cos(phi)*dtheta;
	dy = R*dphi;
METHODS
METHOD on_load;
	RUN default_self; RUN reset; RUN values;
END on_load;
METHOD default_self;
	R := 1 {m};
	theta := 0{deg}; phi := 0{deg};
	dtheta := 1{deg}; dphi := 1{deg};
END default_self;
METHOD specify;
	FIX R,theta,phi,dtheta,dphi;
END specify;
METHOD values;
	R := 6372.795477598 {km}; (* earth's quadratic mean radius *)
	theta := -33.9189{deg};  
	phi := 151.2295{deg};
END values;
END spherical;
1	REQUIRE "atoms.a4l";
2
3	(*
4	simple model for some spherical geometry: latitude and longitude angles
5	subtended by North-South distance (dy) and East-West distance (dx) on
6	a sphere of given radius, given the local latutide (phi) and longitude
7	(theta).
8
9	The 'on load' configuration of this model gives the dimensions N-S and E-W
10	corresponding to a 1 deg-lat x 1 deg-long square in Sydney.
11
12	TODO:
13	More useful calculators such as distance between two points,
14	area of trianges, etc.
15	*)
16	MODEL spherical;
17	dx, dy IS_A delta_distance; (* E-W, N-S *)
18	R IS_A distance;
19
20	phi, theta IS_A angle; (* latitude, longitude *)
21	dphi, dtheta IS_A angle;
22
23	dx = Rcos(phi)dtheta;
24	dy = R*dphi;
25	METHODS
26	METHOD on_load;
27	RUN default_self; RUN reset; RUN values;
28	END on_load;
29	METHOD default_self;
30	R := 1 {m};
31	theta := 0{deg}; phi := 0{deg};
32	dtheta := 1{deg}; dphi := 1{deg};
33	END default_self;
34	METHOD specify;
35	FIX R,theta,phi,dtheta,dphi;
36	END specify;
37	METHOD values;
38	R := 6372.795477598 {km}; (* earth's quadratic mean radius *)
39	theta := -33.9189{deg};
40	phi := 151.2295{deg};
41	END values;
42	END spherical;