Jim. It is always nice to hear someone else give you the measurement of something. Saves one from spilling their drink or grinding the tools.
Only issue is they do not know how heavy/light you have your boat provisioned. They do not know what type of appliances you may have sticking above the mast.
For me going under a bridge presents a significant risk to the boat. I require my helms person to know the actual height for our boat. SO we measure the mast. We measure the distance from the water surface to the deck height at the mast. We know that we have a 3ft antenna above the mast head. And we add a foot to all that just to give us a bit of cushion.
We then review the minimum heights of all obstacles along our cruising path. We check the tidal/river heights for the day/time of transit. And we examine the weather just to be sure there is not wind event pushing the bay/river water to an offsetting height.
While I accept the mast height posted in sail boating data sheets, I verify the actual numbers so that I can trust the boat will have a safe passage.
But that is me. You can do as you please. That is the beauty of boating . Your boat your rules.
