Re: the difference between gauges/measurements, it's a bit like that old saying ...
" If you have one watch - you know what the time is, if you have two watches, you are never quite sure! "
Perhaps you already are aware of this but I put it here as I think it provides good info to folk who are having troubles with the rain gauge.
Rain gauge faults - Davis Weather Stations Knowledgebase - 1
WWW.MANULA.COM
Apparent inaccurate readings The commonest support issue with rain gauges is suspected inaccurate readings. In many cases the rain gauge is actually not at fault...
Hope it helps you or orthers.
Ohm