Measuring current

[Scoobahdood]

Is there such a thing as a hand-held ocean current measuring gage? If not, what is the trick to getting a true since of the current speed. It seems if you dive with a group of 10 divers you get 11 different answers on how fast the current was. Is there an easy answer to this question? :cool2:

 

[Thalassamania]

Yes, there are several sorts of current measures.

Wiki: Until the mid-19th century vessel speed at sea was measured using a chip log. This consisted of a wooden panel, weighted on one edge to float upright, and thus present substantial resistance to moving with respect to the water around it, attached by line to a reel. The chip log was "cast" over the stern of the moving vessel and the line allowed to pay out. Knots placed at a distance of 47 feet 3 inches (14.4018 m) passed through a sailor's fingers, while another sailor used a 30 second sandglass (28 second sandglass is the current accepted timing) to time the operation. The knot count would be reported and used in the sailing master's dead reckoning and navigation. This method gives a value for the knot of 20.25 in/s, or 1.85166 km/h. The difference from the modern definition is less than 0.02%.

Today there are propeller driven current meters. The easiest way for a diver is to remember that a knot is a little bit more than 3 feet per second. Watch something on the surface float by and time it over 6 feet.

 

[Echoo]

Far as surface speed goes just come to a stop and watch the GPS to see how fast you are drifting.... not a exact science but will give you a idea

 

[ShakaZulu]

Lay on your back with your iPhone and run the MotionX application from Garmin

 

[Salmonboy97]

Ive been on the water many times and seen the current running one way and the boat "drifting" another at anchor. So just stopping on the water wont give you an accurate idea of how fast the current below the boat is because it doesnt take into account the wind effects on the vessel.

 

[deepstops]

The easiest way for a diver is to remember that a knot is a little bit more than 3 feet per second. Watch something on the surface float by and time it over 6 feet.

Incorrect Thal, it's just under 1.7 feet per second = 6120'/hour

An actual nautical mile is 6,076'.

 

[Echoo]

Ive been on the water many times and seen the current running one way and the boat "drifting" another at anchor. So just stopping on the water wont give you an accurate idea of how fast the current below the boat is because it doesnt take into account the wind effects on the vessel.

Yes you are correct. I have seen that many times myself..... I guess I kinda forgot that issue... My current boat does not really catch the wind to bad and the boat generally goes with the current. The way I am sure of that is cause I normally drop a buoy and use that to get the direction of the current and anchor accordingly.

Honestly I did not put alot of thought into that first comment. My plotter gives me estimates as to what the current speed is at the tide stations. Granted these are estimates and the open water is diffferant than where the stations are, However it gives me a idea and I plan my trips accordingly

 

[Thalassamania]

Sorry ... must have had a senior moment there, I meant to say a little less than 2.

 

[The Chairman]

I am not aware of a hand held gauge to assist you. I would love to hear about one.

 

[Zieg]

Is there such a thing as a hand-held ocean current measuring gage? If not, what is the trick to getting a true since of the current speed. It seems if you dive with a group of 10 divers you get 11 different answers on how fast the current was. Is there an easy answer to this question? :cool2:

Here's one. General Oceanics Model 2135 flowmeter with a waterproof houseing good to 225 ft.