[folivier]

I think the problem with adjusting tire pressures due to either temp or altitude comes with where are you going? Are you staying at the same altitude for a day or more of driving? Or will the temperature rise to 80 or higher while driving?
I've never adjusted my pressures due to altitude or temp and have found low pressures would climb to the acceptable ranges after an hour or so of driving. But if I had raised the press then they could be over inflated once they warm up or I descend to a lower altitude. These are all readings using a TPMS.
Richard has a good idea to compare axles, just be aware if the sun is warming up the tires on one side the pressure may be higher due to the increased temp.