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April 30, 2009

New Advances in Chart Overlays

Overlays offer key details from top to bottom

A Furuno NavNet 3D screen shows sea-surface temperature (transparency adjustable) and satellite-photo overlays with wind info.
This NavNet 3D satellite-photo overlay reveals shallow water and channel relief at Miami's busy port.
Though not real-time, this Raymarine transducer overlay shows estimated coverage in 3-D.
Capt. Bent has become a true Sirius believer: "When it first came out, Raymarine said I should have it. But I said, 'I've got radar and can see 70 miles.' They said, 'Put it on the boat,'" he explains. "One time in that first year [with weather service], I was 75 miles off the beach. At about 11 p.m., I saw a spot of green off the Virginia/Maryland border. A half-hour later, it's bigger. ... It's coming at us - 40 miles thick. I said, 'I'm goin' home.'

"By 1:30 or 2 a.m., I realized I was going to get nailed. I was able to find the narrowest part of this thing and run through that. The people who stayed out said three waterspouts came through where we had been sitting."

Raymarine's weather presentation does appear a little bit differently than other companies' displays. Raymarine chose to show weather in its own window; however, the data is GPS-aware, so your boat's position is shown in the weather window. Captains can mark a waypoint on the weather side, and it appears on the plotter display.

Data on Data
The software you choose - whether it comes on a separate chip from companies like C-MAP or Navionics or is initially  programmed into the hardware such as BlueChart for Garmin or MaxSea for Furuno - provides you with a load of overlay options including satellite photos, tides and currents, wrecks and hangs,  fishing contours and depth shading.

Photos and information for U.S. data often comes from government sources such as the U.S. Geological Survey and the National Oceanic and Atmospheric Administration. Those agencies update material "periodic-ally," so it can't be real-time...yet.

"What's kind of nice with the current and tide data is that there are several ways to render it - as a graph, table or an overlay," says Jim McGowan, marketing manager for Raymarine, which uses Navionics cartography. "It will show you the lat/lon of tide reference stations, and then visually it looks like a barber pole that represents the height of the tide at whatever time it is."

Current direction shows as multiple arrows. The system can call up the day's tides and show 10- or 15-minute time slices illustrating where tides will be at particular moments in the day.

While surface overlays seem particularly popular, manufacturers do find ways to better show depths and contours. Some provide additional chart data that maps the location of bottom structure; some offer depth shading, which adds a better visual reference; and some offer a transducer overlay that shows - in virtual terms - what your fish finder may be seeing.

One potential subsurface overlay that can only be done right now on MaxSea PC software involves taking real-time depth information from a sounder and literally correcting a static chart. With this personal bathymetric generator, "Guys will motor back and forth and redraw the bottom on their charts," says Furuno advertising and communications manager Jeff Kauzlaric. "If they're going over canyons or wrecks, it repaints the bathymetric data."

With all these overlays, anglers have a wealth of information for both navigating safer and catching more fish. And while that may challenge my friends to do more than pan and zoom, I think they'll be thankful and - ultimately - more successful.