Dale:
It has been one of my pet hates for many years that commercial pressure gauges and pumps badly leak air from the tire, but I now have solved the problem.See my report:
http://home.earthlink.net/~caverhall/pressandcalib.htm
I will have a lot more to report in the near future.
Also, your tire pressure worries during race-course measurement would end if you were able to adopt the constant-pressure method described in the report.
Of course you can tape a course at any temperature, but accuracy will not be as good as if you do it at close to 68F under a cloudy sky.Measurement with correction for temperature deviation is not as good as that done without.Also on a hot intensely sunny day you never really know the temperature of the tape.