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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 09-13-2008
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GPS selection...

Hi All, I'm in the market for a chart plotter GPS and would appreciate some advice about which make/model might do what I want.

Please, just so everyone knows, I have all the proper paper charts for the areas I sail with dividers and parallel rule, 4 magnetic compasses (one portable) and I just ordered a new Uniden VHF with DSC to replace the ancient VHF non-DSC unit my boat came with. I do know how to use all that. I know I can get an inexpensive GPS to plug into the VHF for distress, and this is my primary motivation. You have to know how to navigate and I can do that, but in a pinch, I want anyone on board to be able to call for help and have our position squaked to the USCG and whoever else is listening.

That said, since I am going to have a GPS anyhow, I would like a chart plotter GPS. They look like a lot of fun. I was in Boaters World today and played with one, and it did much more than I expected.

I was looking at the Garmin units, only because I have used Garmin for driving and liked them. I was thinking I would like my GPS to:

- Show my position on a chart
- Display my bearing and speed
- Overlay weather data
- Provide depth sounding information
- Provide wind data

I don't care about:

- Having the GPS plot my course
- Having the GPS pilot my boat
- Crazy fish eye views, 3D views and ariel photographs
- Finding fish

That said, I was looking at the Garmin GPSMAP 440sx. This unit comes with an XM weather receiver, a sounder (but no transducer), a 4in diagonal color screen and coastal charts. I found one as low as $560 delivered. The display screen although nice is pretty, well, mediocre. Its small and relatively low detail.

I really liked the GPSMAP 545s, which has a much higher resolution screen that is an inch bigger. But, here is the catch... Although this unit is not outrageously more expensive than the 440sx, it does not include the weather receiver, which is another $200. So to get a nicer screen I need to spend another nearly $400.

It seems there should be another option. I started to look at other brands, but the selection got to be dizzying.

Does anyone know of a nice solution for a GPS unit that will do those things above but is a bit nicer than the 4 inch low-res screen the 440 has?

Also, does anyone know how these units interface to wind speed and direction sensors?

Finally, the boat has a through hull transducer mounted and cabled to a Nexus display. Can I use the same transducer or will I have to change it?

Thanks very much...
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Old 09-13-2008
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One problem you will run into is that you're looking for a very specific set of features, some of which are only included in higher end units. Higher resolution screens are generally bundled with some of the features you DON'T want—since they're generally needed to display the aerial photographs and fish-eye views, which are features some people are wanting.

Almost all GPS chartplotter units wil show your position on a chart, display the bearing and speed as well VMG, SOG, and other such data.

Only certain models will show the weather data—be aware that the weather data service is a SUBSCRIPTION SERVICE, and requires you pay a monthly subscription fee.

The Wind Data is a tougher one, as I pointed out above. Most of the GPS plotters I've seen out there won't display your wind instrument data on them. It just isn't offered as an option generally, except on the higher end system units. For instance, you can get wind info displayed on the Raymarine C-series multifunction displays. So, if you got a GPS chartplotter from the manufacturer of your wind instruments, like using a Raymarine chartplotter with ST60 wind instruments, it is far more likely to allow you to display wind instrument data, but I don't know of any of the third-party GPS units that will display wind data from instruments.

Most of the units that show depth data are combination chartplotter/fishfinder units—that's the market they're catering to, and you will pay extra for the fishfinder capabilities, even if you don't want/need them.

That said, some of the plotters will display depth information via an NMEA 0183 or NMEA 2000 data feed, but most use their own transducer to display it. Again, if you're using a chartplotter from the instrument manufacturer, the chance of being able to use the existing depth sounder info goes up.

BTW, most of the stand-alone third-party chartplotters only support the input of limited NMEA sentences, usually DPT (depth), MTW (water temperature), and VHW (water speed & heading). They don't support NMEA input of MWV sentences generally, which is wind speed and direction.

It would help to know what instruments you have aboard. BTW, the XX5 units from Garmin have better screens than the XX0 units IIRC, and the 545s would be a higher resolution screen than the 540s—VGA vs. QVGA—so you're actually looking at a model that is two higher than the 440s.

I'd also recommend you read the post in my signature if you haven't already to help you get the most out of sailnet.
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Last edited by sailingdog; 09-13-2008 at 07:45 AM.
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Old 09-13-2008
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I have a Raymarine 435 that's available. (I upgraded to a multifunction with radar.) It's a current model, MSRP $1,100, in great shape. It would come with the antenna, but without the Navionics chip. I hate to see it sit in my basement, so any reasonable offer would be accepted. If you think it might be of interest to you, PM me.
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Old 09-13-2008
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I have an aviation GPS with XM weather and think its the greatest improvement in aviation safety since the advent of GPS itself. That said, I'm not sure I could justify the cost of the XM weather just for use on the boat. Getting caught by a typical summer thunderstorm while out on the boat might be a bit scary, but it would almost certainly not be the life threating situation that getting caught by the same storm in my airplane would represent.

IMHO, about the only thing the XM could help with (that you can't get from the VHF) for the average weekend sailor is deciding when to drop the sails in adavance of a storm which you should do sooner rather than later anyway.

If you are are doing longer offshore passages (but staying in the coverage area) it might be worthwhile, but its something I think most recreational sailors should view as a "nice-to-have" luxury vs. a deal breaker feature.
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Old 09-13-2008
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Nmea 2000

Hello,

IMHO, you should do a little research on NMEA2000. This is the new interface for various marine devices. There are many benefits. To learn a little more, visit here:

LowranceNET and NMEA 2000 Networking | Lowrance

Anyway, I have a Lowrance GPS system, and you should at least check them out. The basic 5" screen has 480 X 480 resolution and looks very good. It can interface with both the old NMEA 0183 and newer NMEA 2000 instruments.

I don't know how you would get weather info, but I think you can get the rest of what you want.

Good luck,
Barry
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Barry-

I doubt that any of the Lowrance units will allow you to display wind speed and direction, which is a request. Lowrance doesn't make wind instruments. I checked several of the manuals for their LowranceNet products, and none have any options for showing data from wind instruments.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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Old 09-13-2008
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SD has you covered here but I'll tell you dropping a couple of your features, I got the Garmin 440s for about 400 bucks and it's been a perfect, portable, easy to use GPS. You can pay for the extras on it if you'd like. Once you go garmin you'll be tempted to stay garmin for inter-instrument-communication.


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Thanks very much everyone! This is great information.

I'll check out the Raymarine and see if it is something I might be interested in, thanks!

NEMA is something I need to check out. To answer about what instruments I have on board now, I have a Nexus "multi control" that works for depth and nothing else. There is an anemometer on the mast head, but it appears to be not connected to anything, or else the generic wind speed indicator in the cockpit is broken. The prior owner told me it is not hooked up so i tend to believe him, but I'll check.

I can live without some of the features I listed, even the weather. I knew it is a subscription service, and maybe I'll get bored of it quickly. I just thought it would be good to have a single device that gives a big picture, rather than separate devices for depth, wind and so on all over the place.

Those were good points about the xx5 Garmin units having higher res due to the overheat photography and such. Still, from looking at a store, it seemed that the charts were much sharper with more information easier to read. Also, I was surprised how big a difference there is between a 4in and 5in screen. I think the 5in would be much easier to see from across the cockpit.

One thing that i have been thinking, getting back to NEMA for a minute, is that it must be possible to convert analog - or maybe even digital - sensors to NEMA. I am thinking a single PICK processor could do that job as an interface between the sensor and anything that consumes NEMA. I'll read up on NEMA before I ask more about it, thanks for the link!

For another GPS question, do the internal antennas work well if the unit is mounted in the cabin of a fiberglass boat?

Thanks again!
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Old 09-14-2008
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The GPS receiver is going to be iffy inside fiberglass--I believe this is according to Garmin. If you do the flush mount, they recommend the external antenna, IIRC.

We've got the 545s and we like it a lot (mounted on pedastal).
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Old 09-14-2008
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I use an older Garmin with the integrated antenna inside the boat all the time... no problems whatsoever. The newer ones work even better... since they're more sensitive.

As for converting analog or digital sensors to NMEA, it really isn't necessary, since many sensors can output NMEA signals.

It also sounds like you may be looking to replace your instruments... I would highly recommend the TackTick instruments. They have a kit that includes Wind, Speed, Depth and Temperature and has the NMEA interface box.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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