I'd like to call this dialing up a 63 year old memory. I ran across the setting in the picture on my morning walk. I came home and read more than I should know about sundials.
Seems the first mention of them is in the Bible (Isaiah 38:8 and II Kings 20:9) if you are into that documentation. Most of the physical remains from earlier times (pun) are in the form of obelisks and shadow clocks.
During one extended canoe trip at summer camp, our leader, a fella named Dave Catron, had us all paddle ashore as there was a good chance of mis-reading a map and we were just near what I would call a fork in the stream; one way was back to camp, the other would have found us in Lake Superior in a canoe. He took out his compass and we got our bearings and the map could be read.
One of the paddlers asked what time it was but we had set out with only a compass and map - nothing else allowed - a true adventure for a 12 year old.
He explained that we could make a sundial and tell the time of day (if we had enough time to make it back or should we find a place to camp). He aligned the compass to North and drew a line in the sand. We made a circle around the line, found a straight piece of dead branch called a gnomon (by the way - an excellent crossword puzzle word to know) and figured out that we were sticking it in the sand about 45 degrees toward the north.
The rest was pretty easy.
That was a zillion years ago. I had forgotten all about it until this morning's walk.
One of the paddlers asked what time it was but we had set out with only a compass and map - nothing else allowed - a true adventure for a 12 year old.