An attempt to implement the International Standard Atmosphere in Octave.
In the Aeropsace toolbox for MATLAB, there is a function called atmosisa.
This should work as a drop in replacement for that function, and hopefully implement the ISA correctly.
To the best of my knowledge MATLABs atmosisa only works for altitudes between 0 and 20000 m.
This Octave version should, however, work for the complete range from -610 to 84000 m.