I went to a training session for a local ambulance squad that is starting up a light search and rescue team. They want to do rescues in their immediate area that just involve guiding lost people out of the woods, or carrying injured people out of the woods. No high-angle or through-the-ice rescues. I'm a member of Civil Air Patrol and went so I'd be aware of what nearby agencies were doing.
One of the folks asked about datums, and was under the impression that all the stuff printed in the margin of a map, such as latitude, longitude, scale, etc. was the datum. I tried to explain, off the cuff, that a datum was the system used to decide the exact latitude and longitude of any point on the ground, but I'm not sure I made it clear.
So, does anyone know of a simple explanation of what a datum is, that only emphasizes the differences that people looking for a person with a hiking GPS will care about?
Also, is a term that collectively includes most of the stuff you find in the margins of a map?