Folks,
Time and distance are fixed so groundspeed is the issue. If you have little or no ability to vary the groundspeed then you need to determine your rate of progress to determine your arrival time at some point. Distance markers make it easy to determine that rate of progress. If on the other hand, you can vary the groundspeed to control your rate of progress, then time markers make it easy to achieve your time on target.
The only time that time and distance markers are interchangeable is when everything matches the plan. Otherwise, inappropriate markers create confusion, the very antithesis of marking the map in the first place.
Navigation cycles should be related to the clock.
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Stay Alive,
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