What does "FSW" stand for?

[SwimJim]

Then theres the ever popular FOW = feet of water

 

[Fish_Whisperer]

Then theres the ever popular FOW = feet of water

I like this one better.

 

[The Chairman]

Most (not all) depth gauges are calibrated to FSW. All tables that I have seen are also calibrated to FSW.

Knowing your FFW is nice, but keeping your Depth gauge in sync with your table is essential.

 

[miketsp]

..snip..
When I was flying, I would often state that I was ____ feet agl. (above ground level, as opposed to, above sea level)

Now that will confuse everyone. Were you bragging because you had a radar altimeter or did you mean feet above the height of the reference airport that gave you a QFE as opposed to a QNH?
Ground level is generally not the best reference as it has a nasty habit of varying. Especially around mountains.

 

[H2Andy]

Our computers and depth gauges read only the pressure to get the depth, right? I assumed mine's set to salt water, and I'm actually 2-1/2 percent deeper than it says if diving fresh, since fresh water's less dense?

yep... as NetDoc says, most computers are set to FSW.

some allow you to change between FSW and FFW (the Nitek He, for example)

 

[Fish_Whisperer]

Now that will confuse everyone. Were you bragging because you had a radar altimeter or did you mean feet above the height of the reference airport that gave you a QFE as opposed to a QNH?
Ground level is generally not the best reference as it has a nasty habit of varying. Especially around mountains.

Well, I was flying an ultralight with only five gallons of fuel and horrific drag ratios. (Powered parachute: Ram air chute with a steel cart beneath it.) All of my flights were local and over cow pastures, etc. Private airstrip, no tower.

 

[padiscubapro]

yep... as NetDoc says, most computers are set to FSW.

some allow you to change between FSW and FFW (the Nitek He, for example)

Don't forget there are also vary definitions what a foot of sw is..

The europeans use 1 specific gravity of water so that 10m of water is 1 bar, the definition by NOAA and the us navt is different.. there are actually 2 of tehse one is so that 33 fsw of water = 1 standard atmosphere, another is that 33.066 feet of sw = 1 atmosphere

here are the actual definitions

The actual defination is..

10 m of salt water having a specific gravity of 1.01972 is 1.00 bar


for comparison
the us NAVY assigns a specific gravity 1.02480 so 1atm = 33.066 fsw, which is normally refined to 33.00 fsw

so depending on which defination you use the conversion fsw to msw is

for 33.066 is 3.2633 fsw/msw
or
for 33.000 is 3.2568 fsw/msw

 

[blubberboy]

Most (not all) depth gauges are calibrated to FSW. All tables that I have seen are also calibrated to FSW.

I have never seen a table or depth gauge calibrated in FSW. You know there is a whole wide world out there that uses the (whispers) "metric system".

Shock horror!

PS: Is there any irony in the fact that the US uses the "Imperial system" :devil_3:

:mischief:

 

[Packhorse]

.

 

[SeanQ]

Most (not all) depth gauges are calibrated to FSW. All tables that I have seen are also calibrated to FSW.

Knowing your FFW is nice, but keeping your Depth gauge in sync with your table is essential.

My Uwatec bottom timer is metric and calibrated for metres fresh water.

The pressure is important, not the actual distance to the surface. While my bottom timer may say 10m while in the ocean, I know I am actually slightly shallower than 10m. If the gauge displays 10m, I'm at 2ata regardless of what the water tastes like.