I have a kestrel 2500 NV, the problem I'm having is with the altimeter part. The problem is it won't give consistent readings over time. I've done all the things I'm supposed too, I looked up my address on a topo map zero the reference baro so my alt reads what the topo map said my elevation, then go to the reference alt and set that so the baro reads correct but the dang thing is always off when I get back and check it! I called kestrel and they said you have to re calibrate it very often. But today at 1130 am I calibrated it and them checked it at 1100 pm and it was off by 90 ft ( calibrated at 233 ft and now reads 140 ft). Are other kestrel users having this issue? Seems almost like a useless feature if it loses it's ability to accurately give me the altitude/elevation. So what have other kestrel user found, and is this normal for these units? Can't imagine losing calibration in 12 hrs is acceptable or reliable!