In case you don't know about these altimeters, they have to be calibrated every day to a know elevation and if there large weather fronts moving through your area, you have to calibrate more than once a day. (Not small calibrations, large ones, sometimes very large) So then if you don't know your current altitude, you can only gauge the relative change from an arbitrary fixed starting point. Kinda fun for a day or so, then after that, boring. Just one person's opinion though.
Greg