oops , I'll get me coat
Just shows you not to trust what a 2nd year engineering undergraduate says at midnight.
I imagine the temperature of the gas in the oleo could be monitered straightforwardly allowing compensation. Of course none of this gives you an inflight reading, and a bit of rain would add a fair chunk to the weight too.
Out of interest are aircraft weighed at at any maitenance checks? As I understand that light aircfaft have a habit of putting on weight throughout their lives, does the same aply to the big stuff?