I tend to leave my GPS on all day when in the field.

I'll download the track data for future presentations in the classroom.

I find that my batteries last through the day. At the end of the day I'll dump the batteries and put new ones in and then calibrate the GPS receiver's compass.

That way I am ready to go the next day and don't have to fuss around calibrating.

Blake

www.outdoorquest.blogspot.com