View Full Version : Question about reading nautical charts


Rockport24
05-07-2007, 12:40 PM
Hey guys, what do depth numbers in parenthesis mean?

MakoMike
05-07-2007, 12:43 PM
Don't understand what you mean.

Rockport24
05-07-2007, 12:47 PM
The numbers that indicate the depth of the water, some times they are in parenthesis like it will say 5, then right next to it (7) or something like that.

Sweetwater
05-07-2007, 01:04 PM
Sometimes when data are presented in charts and graphs numbers in parenthesis will indicate the number of measurements taken (in this instance the number of soundings taken to derive the avg. depth). But I'm only guessing as far as a nautical chart goes.

Rockport24
05-07-2007, 01:10 PM
yeah, if it helps, a lot of the numbers in parenthesis are near rocks

Rick Ackley
05-07-2007, 01:22 PM
Could you be looking at small humps and the numbers are breaking the outline?

daceman63
05-07-2007, 01:25 PM
the legend on the chart will describe ever detail. check there for the specifics for your chart. Usually for lights and or other extra detail are in parenthesis that might tell you their flash codes.... ie: Fl (1+4+3) for Minots...with other info such as the height and how far it can be seen...not usually in parenthises...

as well as the aforementoned warnings for rocks and such...

but definately check out the legend on the chart you are referring to...

Gunpowder
05-07-2007, 08:29 PM
also sometimes when the parenthesis are near rocks, it means that the top of the rock is three feet below the water line at mean low tide. when there is an * , it means the rock is above the water line at mean low tide and is visible.

Gunpowder
05-07-2007, 08:30 PM
shoulda said if the chart looks like this: (3) , it means that the rock is three feet below, but this number changes where the rocks are, its obv not always three feet for every rock if i had confused anyone in my last post.

Clueless
05-07-2007, 09:27 PM
Parens are used for some types of depth soundings (http://chartmaker.ncd.noaa.gov/mcd/chart1/hydro/I.pdf) or rocks that are above water at some point (http://chartmaker.ncd.noaa.gov/mcd/chart1/hydro/K.pdf). Might be some other reasons too.

Roger
05-08-2007, 07:02 AM
Parentheses identify soundings or height that are out of position. IOW, the numbers are not directly over the spot to which they refer, but usually adjacent to them. On some charts a line is drawn to the referred structure instead of parentheses.

Rockport24
05-08-2007, 08:53 AM
thanks for all the help guys, I think I got it now!