function rho = density(h)

%	This is the density calculator based on height.  It is based on the US 
%	Standard Atmosphere of 1976.
%	Source: http://scipp.ucsc.edu/outreach/BALLOON/Atmosphere/1976%20Standard%20Atmosphere.htm
%

%	VARIABLES and UNITS
%
%	conventions:	Large arrays are in all caps
%						Vectors and other variables are in mixed case, as appropriate
%
%	h					:The height above sea level, in m.
%  rho				:Density of the atmosphere, in kg/m3.
%	rho_o				:Density of the atmosphere at sea level, in kg/m3.


global data;
global index;


%	CONSTANTS
rho_o = data(1,92);		% kg/m3 



% MAIN PROGRAM
   
if (h <= 11000)
   rho = rho_o * (1 - h/44329)^(4.255876);
   
elseif (h <= 20000)
   rho = rho_o * (0.297076)*exp((10999-h)/6341.4);
   
elseif h <= 32000
   rho = rho_o * (0.978261 + h/201010)^(-35.16319);
   
elseif h <= 47000
   rho = rho_o * (0.857003 + h/57944)^(-13.20114);
   
elseif h <= 51000
   rho = rho_o * (0.00116533)*exp((46998-h)/7922);
   
elseif h <= 71000
   rho = rho_o * (0.79899 - h/184800)^11.20114;
   
else 
   rho = rho_o * (0.79899 - h/184800)^11.20114;			% same as <=71000
   
end


data(index,92) = rho;