speed? Easy! Use a mobile phone app!
they are not very good. It may get better as time goes by, but
there are basic issues.
are designed to give instantaneous speed. In a two second refresh
interval, the boat has probably moved 15 feet? The sat nav
coordinates are not changed much. The timestamps may be very
accurate, but the figures on the screen flicker too much.
need to know whether we are doing 4.3 mph or 4.4 mph.
that are not steady and flicker by 0.2 mph don’t inspire
are practical problems.
Motorways are well served with mobile
phone mast coverage.
river also flows – so upstream speeds are different to
winds have the same effect.
And another factor – rivers
are not straight. Far from it.
how do boats measure their speeds? Most river boats
boat speed meters use paddle wheels and are intended for far
have even calibrated a water flow meter paddle wheel with an
arduino and towed it
alongside Stirling craft. It worked, but
I have found a better way.
the Thames authorities instituted a speed limit on the Thames,
they had the same
The placed transit posts at various places along the river. The
spaced so that if you passed them more quickly
than one minute, then you were exceeding
the 5 mph speed
you need still water, no wind, and a decent straight run.
solution is a timer on my wrist watch and a notebook.
favourite place is upstream of a lock that has a long, relatively
straight, lock cut.
the boats exit the lock, going upstream, there is no water
Both banks are tree clad. Wind is low.
exiting the lock gates, I start the timer. When I reach the end of
the lock cut,
I note the time.
Bridges are equally good
markers. Or if there is a large boat moorings near you, they
often still water and you can pick a straight stretch.
home, I use Google maps to measure the distance.
“right button” gives a menu to measure distance. You
can trace a curve to follow the river bends. 2,184 feet in 5 mins
36 secs = 4.43 mph