It never fails to amaze me how oblivious the vast majority of folks are when using them there smart phones. The conversation went something like:
Guest: It's really hot, is there somewhere we can swim in the mountains?
Me: Sure, there's a place called Caramella with waterfalls and pools about 12km away. You have a GPS in the car, right?
Guest: Yes, and on my phone.
Me: Here are the latitude and longitude co-ordinates... (on a piece of paper with co-ordinates in decimal form)
Guest: What are co-ordinates/latitude/longitude?
Twenty minutes pass and guest returns.
Guest: My GPS doesn't work with co-ordinates.
Me: You may need to convert to degrees/minutes/seconds format.
Guest: What are degrees, minutes and seconds? And what do N, S, E and W mean?
This is the point at which it just becomes easier to take the guest's car keys and programme the GPS myself. I predict a "We're lost!" phone call later in the day.