posted 02-13-2014 03:17 PM ET (US)        

For Rip Van Winkle it took a 20-year nap for him to become out of touch with his society. In the field of modern marine electronics, you can become confused if you are out of touch for 20-days. In that regard, I am not sure when Garmin first mentioned their GPSMAP 840xs product, but it has really got my attention today.

With a suggested retail price of only $1,500, the Garmin GPSMAP 840xs delivers a lot of electronics for the money. It is a combination of GNSS receiver, chart plotter, and SONAR. Let's look at those three facets.

The GNSS receiver is internal to the unit and provides three areas of improvement over the prior generation of marine GNSS receivers:

--it works with both the Air Force NAVSTAR GPS and the Russian GLONASS systems. The principal benefit of this dual-system receiver is to increase the number of satellites in view. The more satellites in view, the better the chances for a lower dilution of precision;

--it provides a position solution at rate of ten times per second (i.e., 10-Hz). The more frequent position solution is said to improve the accuracy of the course over ground track, and this improves the course heading deduction; and,

--it is said to offer improved sensitivity compared to other devices. The precise sensitivity is not quantified, but is just said to be "high." It can also be used with an external antenna.

The chart plotter is provided by a 8-inch diagonal color screen of 800 x 600 pixels. This is the old-style 4:3 aspect ratio, which I think is better for chart presentation than the newer wide-screen 16:9 displays often seen. The display is color, of course. There are no specifications for brightness or contrast ratio; I assume it is a good sunlight-viewable display. It is rated for IPX7 waterproof environment. There are two SD memory card slots.

Like all Garmin chart plotters, the GPSMAP 840xs includes Garmin cartography. For coastal charts the unit comes with the Garmin BlueChart g2 "maps"; for inland charts the unit comes with the new Garmin LakeVü "maps". It can also work with the optional and more enhanced LakeVü HD Ultra or BlueChart g2 Vision charts.

For interconnection to other devices, the GPSMAP 840xs has two NMEA-0183 bi-directional ports and one NMEA-2000 network interface. There is also an ethernet port, called a Garmin Marine Network port. The GPSMAP 840xs does not interoperate will all of the other Garmin network devices, but it does work with a subset of them. This limitation sounds reasonable. With only an 8-inch display, you cannot really put too many different functions on the screen at one time. Garmin is probably reserving the full network interoperation for their larger and more expensive displays.

The GPSMAP 840xs also includes some specialized features of interest to sailors, such as lay lines, tide and current features, and other navigational functions of special interest to sailboat racers.

The SONAR in the GPSMAP 840xs is likely the biggest innovation. For some time Garmin has been recognized as top-flight in GNSS and mapping technology, but their SONAR components have been perhaps not at that same level. In the 840 the SONAR seems to be all new and up-to-date. Using continuous-wave frequency modulated signals on transmit and digital signal processing on receive--often called chirp technology--Garmin delivers an advanced SONAR. There are really three modes of operation available:

--a tradition pulsed SONAR with a 1-kW power rating;

--a chirp technology SONAR; and

--DownVü scan, a Garmin trade name for a high-frequency downward aimed SONAR, also with chirp enhancement.

The electronics and software for all three types of SONAR are apparently contained in the GPSMAP 840xs. The unit is sold without a transducer, so you must buy the transducer separately. Selection of the transducer determines what sort of SONAR you will be able to use. Choices are from:

--AIRMAR P66 depth, temperature, and paddle wheel speed, dual frequency 50/200, 600-watt tri-ducer; $160

--Garmin depth and temperature, dual frequency 50/200, 500-watt; $83

--AIRMAR TM150M chirp depth and temperature transducer, 95 to 155-kHz 300-watt: $300;

--AIRMAR TM260 chirp depth and temperature transducer, 50 to 200-kHz 1,000-watt: $1,000;

--Garmin All-in-one traditional and DownVü transducer, 77/200-kHz and 455-kHz, 500-watt; $100

posted 02-13-2014 03:35 PM ET (US)            

http://www.unwords.com/view/pronounce.html

which suggests that the U with umlaut is pronounced in German like the U in frugal.

posted 02-21-2014 09:09 AM ET (US)            

1. Garmin has a long history of keeping it's products up to date with technology. What this has meant to me is that the last six GPS products I have purchased from them has been superseded by a new and improved model in 6 months or less. Not the end of the world but it is annoying to drop thousands on the latest and greatest and get second fiddle in 4 months.

2. Proprietary charts. Expensive, enough said.

3. Garmin tends to utilize more graphics than Simrad. The charts themselves are similar. It's the user interface. I can appreciate the pop up keypad that is 6"x6" with my 52 year old eyes. That becomes a moot point when I can not see the depth display while running a channel though.

4. Garmin accessories have been somewhat unreliable over time. Two depth sounder modules later. Two GPS antennas because WAAS reception does not work. Two transom mount transducers (not Garmins fault)

posted 02-24-2014 11:45 AM ET (US)            

quote:

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I also think a chart plotter that lacks a numeric keypad to be tedious to use...

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