function [rho]=alt_dens(h)
%
%	density = function (altitude(m)) ISA standard
%
sigma=h;
if h < 11000,
 sigma = (1 - h*2.2558e-5)^4.2559;
else
 sigma = 0.2971*exp((11000 - h)/6341.5987);
end;
rho=sigma*1.225;
end