Depth Soundings by Color Code for the World ?

[H Romberg]

Hi folks. I heard this was a nice place to talk sailing in a polite environment. Looking around, it seems like a good crowd. Thanks for setting it up.

On to the question: Does anybody know of a chart product that color codes the waters of the earth by color? I'm buying a boat that is kind of deep,(6'6") and I'd be interested to see how much each foot of draft shrinks my cruising grounds. It'd be great to be able to zoom in on an area and have chart soundings shown as colors, but I haven't found a product that does it.

On second thought, Maybe I don't want to see it.

[GordMay]

Hal:
I think we (as cruisers) would probably be more concerned with Coastal water depths, rather than with world oceanic depths (see below). Unfortunately, the scale of such a world coastline chart would be totally unworkable.

Practically speaking, your draft of 6 ½ feet will be considered “deep” for many favourite coastal cruising areas. However, many shallower coastal waters can be safely (though inconveniently) piloted, by playing the tides.

Oceans cover about 140 million square miles (362 million sq km) ), nearly 71% of the Earth's surface, to an average depth of 12,200 feet (3,720 m), with the deepest sounding being 36,198 feet (11,033 m) in the Mariana Trench (Western Pacific Ocean).

There are shallow seas around most continents, that cover gently sloping areas called continental shelves, which reach depths of about 650 feet (200 m). The World has over 882,000 nautical miles (1,634,700 km) of Coastline*.

* Measuring coastline is a fractal problem.
ie: You could measure a coastline with a stick 1km long, get an answer, then try one 1m long and get another answer, then one 1cm long, 1mm long, and so on. Each time, the "answer" would be longer - notwithstanding the difficulty of deciding where the actual boundary between sea and land lies.

Canada's coastline is the world's longest at 131,553 nm (243,792 km or 151,485 mi.), including the coastline of the country's 52,455 islands.
The coastline of the U.S.A. is about 10,755 nm (19,924 km or 12,383 mi.).

There are over 175,000 square nautical miles (600,000 square kilometers) of coral reefs in the world’s tropical and semi-tropical seas.

Tidal ranges are usually small in the middle of the ocean, but can be very large where tidal waters are funneled into a bay or river estuary. Hawaii has hardly any tidal range at all, while the water in the Bay of Fundy (Canada) has a range of about 40 feet.

Because the survey vessels, that gather hydrographic depth data, have great difficulty maneuvering near-shore, the “traditionally” charted depths are often less accurate for shallower waters. In recent years airborne bathymetric surveys have gained considerable commercial success in the mapping of shallow waters. Satellite radar data is also being successfully used in many parts of the world, offering an alternative, faster and lower cost way to map large areas of shallow waters.

[Alan Wheeler]

Gord, your just a wealth of information
Romburg, when you said "cruising ground" do you mean an area you frequent, or are you talking the world, as in Gords reply. For a local cruising ground, you could buy a Bathemtry chart. It uses colour to show depth to a greater scale than a standard chart. But I suspect you are asking for Software by a couple of things you said. So sorry I can't help you there. Good to see you here by the way.

[delmarrey]

Hal,

What your looking for is Bathymetric Data. Try these links below for a start.

http://www.ngdc.noaa.gov/mgg/mggd.html

http://www.ngdc.noaa.gov/mgg/bathymetry/multibeam.html

http://topex.ucsd.edu/marine_topo/mar_topo.html

And welcome aboard................._/)

[Bev & Bill]

Over the last couple of years they have begun selling forward seeking sonar which samples depth forward from surface to 90 degrees. The price seems fairly reasonable for such an advanced technology and we believe will prove to be very beneficial as a safety factor for questionable charts and shallow water.

[Alan Wheeler]

I understand the forward looking devices. I understand how a standard Depthsounder/fish finder works. But what is the difference with a device when it is called Sonar. Is it the way the info is processed and displayed, is it what frequency and how it is deployed?? Or is it just name? What is the difference

[Talbot]

The nearest to your product is that supplied by Winchart Nexus

[Jentine]

SOund NAvigation Ranging - a method or device for detecting and locating objects especially underwater by means of sound waves sent out to be reflected by the objects; also : a device for detecting the presence of a vessel (as a submarine) by the sound it emits in water
side scan SONAR - a sonar that scans the ocean floor to the side of a ship's track and is used especially for mapping the ocean bottom

Depth sounders use a radio frequency to detect the bottom. Other than the frequency and the means of interpreting the data, I can see no difference. IMHO

Jim Kane

Side scan SONAR - Next toy

[Wahoo Sails]

A few comments.
When I first saw the 3D bathrymic computer programs I said WOW! Figured I would have to have one ... then I queried where the data for those charts came from ... turns out in our area the data comes from the NOAA charts. Since we have a soft sand bottom, the contours change with every storm ... and consequently NOAA makes no effort to keep the depth contours current ... they would have to sound this area every few weeks during the Summer months ... an impossible task. Such programs are available for our area, but I always advised my customers "If you want to know what the bottom was like in the 1950's .. this is great .. but that's not what it looks like now."
As for "forward scanning sonar", on the first page of the owners manual, it advises the owner that it will take some time & patience to learn to read what they are seeing. Guess my customers didn't have the time or patience, most of the units were returned to us as "defective" ... no, there wasn't anything wrong with the units, the customers simply couldn't figure them out.

L S/V Eva Luna

Bob

[gpshephe]

I'm interested in this too. For another reason than coastal waters. I.e., where are the shallows in the middle of oceans, 50 foot waves start to peak and break, where are oil rigs located? Things like that . without having to buy all the maps of the world where can this be found? I have google earth and I've been using it a lot, but it doesn't seem to keep ocean depth well. Places that I know are 40-50 feet, it shows as 0. Things of this nature. Please don't tell me CPM. I cant make that work which is a topic for another thread.