%Model file: trapezod.m
%Comments: The model file, trapezod.m, is an example of trapezohedron
%model from Coggon (1976). This example shows how
%model parameters are to be given. The variables are Ncor = number 
% of corners of the model; Hintn = total intensity of
%ambient magnetic induction, gamma; Hincl = inclination of
%Hintn, degrees, downward from horizontal; Decl=declination
%of Hintn, clockwise from north; Susc = magnetic volume susceptibility
%in units SI, a dimensionlessnumberequal to ((c)ör  -1),
%where (c)^r = magnetic permeability of the model relative to
%free space; Mstrength, Mincl, Mdecl = magnitude (gamma),
%inclination and declination (degrees), respectively, of remnant
%magnetic induction; Nf = number of faces; Fht D height of observation
%plane above origin, meters; and dens = density of
%model, g/cm3.
calgrv=1; % Change to zero if gravity field is not required
calmag=0; % Change to zero if magnetic field is not required
Ncor=8; Hintn=50000; Hincl=50; Decl=0; Susc=0.01;
Mstrength=0; Mincl=0; Mdecl=0;

%Comments: Corner is an array of x, y, z coordinates of corners
%in meters, one in each row, in a right-handed system with
%x-axis northward, y-axis eastward, and z-axis downward. Corners
%may be given in any order.
Corner = [-1000 -1000 0; -1000 1000 0; 1000 1000 0; 1000 -1000 0; -1000 -1000 1;
-1000 1000 1; 1000 1000 1; 1000 -1000 1];
fht=2; dens=2.67;
Nf = 6;

% Add fht to depths of all corners
Corner(:,3)=Corner(:,3)+fht;

%Comments: In each row of Face, the first number is the number
%of corners forming a face; the following are row numbers of the
%Corner array with coordinates of the corners which form that
%face, seen in ccw order from outside the object. The faces may
%have any orientation and may be given in any order, but all
%faces must be included.
Face=zeros([50,9]); % Initialize a sufficiently large array
Face(1,1:4)=[1 2 3 4]; Face(2,1:4)=[8 7 6 5];
Face(3,1:4)=[2 6 7 3]; Face(4,1:4)=[1 4 8 5];
Face(5,1:4)=[4 3 7 8]; Face(6,1:4)=[1 2 6 5];

%Comments: Rectangular grid of stations for computing fields.
%Profiles are along the x-axis (north-south direction). All values
%are in meters.
s_end= -320; % Starting value of x; south end of profiles
stn_spcng = 40; % Stepsize in north direction; stn interval
n_end= 320; % Last x; maximum north coordinate
w_end= -500; % y value for westernmost profile
prof_spcng=50; % Profile spacing
e_end= 500; % y value for easternmost profile