I've heard the term "dead reckoning" forever but never knew what it meant: I guess it's a 4-state Kalman Filter.

The time aspect of distance estimation was the one I never appreciated much until the event that caused me to begin this thread. It was a dark, cloudy night in unfamiliar territory. My phone was dead and so I didn't have the map or GPS I'd used to select and reach the off-trail spot where I was. Recovering from a stomach bug,thirsty, and finally able to hold down water and move I knew I had to find an obscure road trace off of a long, straight pipeline trace with few landmarks. Thanks to a paper map I knew that the junction was just about two miles from where I was. It's surprisingly hard for me to estimate the passage of 45 minutes in my head. I was glad to have my mechanical watch and tiny watchband compass. I still overshot a few times, but I eventually found the road trace and the creek I was looking for and was quite a bit more comfortable at the pickup point the next morning.