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Help on GPS unit and Ruminations

Discussion in 'Boat Electronics' started by CGB, Feb 13, 2007.

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  1. CGB

    CGB Guest

    I'm about to buy my first GPS for my boat because my LORAN finally died. I
    boat in coastal New England. I am inclined to get a GPS that also includes
    a depth sounder/fish finder. I know next to nothing and would appreciate
    any help.

    1. Best brand? Garmin, I know is common. I saw a Lowrance (model
    LCX-28C-HD) that looked very nice at the boat show.

    2. Do I understand that when you buy a GPS it doesn't come with the charts
    built in? That's an extra cost? I see some advertised as
    "GPS/chartplotters." Is there a difference between a GPS unit and a GPS
    unit with "chartplotter?" Without the charts, what does it do for you, just
    give lat/long? How much extra to get the charts, typically.

    3. If I have to buy charts, what brand do you recommend? How do I get
    updates to them, via web, CD, flash memory, etc. Is this necessary (charts
    do change). And, is this yet an additional charge?

    4. Depth/fish sounder needs a transducer. This is an additional charge??!!!
    I would prefer a thru-hull but if I'm reading things right, these are
    expensive, like a couple hundred $. Are transom mounts OK? I'd like
    fishfinding, water temp., and depth.

    5. Internal vs. external antennae. I think some of the models I looked at
    even charge extra for the antenna and bracket!! Mine will go on a flybridge
    covered only by a cloth canvas top with minimal stainless steel support
    work. Would an internal antennae be OK? (lady at West Marine told me it
    was "line-of-sight" and the canvas top would prohibit reception through it
    because you can't see through the top!!! That's gotta be incredibly stupid,
    doesn't it?) As long as I'm spending the money for this, is there a model
    as described that would also serve in my auto, using a plug to the cigarette
    lighter? Or, am I engaging in wishful thinking? But, I do spend far more
    time in the car than I do on the boat here in New England.

    6. In other words, I'm rather lost and would appreciate any help. I've
    seen a lot of GPS units advertised for $500-$700 and thought I'd likely have
    to spend in that neighborhood. Now thinking that I may have to buy the
    bracket, the antenna, the transducer, etc. etc., all extra, it's getting to
    look like maybe I ought to just get my LORAN fixed or get a new compass and
    parallel rules and use them with my $12 digital watch. (for you youngsters,
    that's called dead reckoning).

    Thanks, in advance, for any help.

  2. The manufacturers have the full descriptions of their products on
    their websites, usually including down-loadable manuals and "what's in
    the box" lists. These websites, or your local dealer, should give
    more reliable information than you'll get from the random
    recollections of newsgroup inhabitants.
    "What's Best" questions can start religious wars! (However, I prefer
    Garmin, because that's what I started with.)
    A basic GPS receiver will give you position, speed and direction of
    travel, and will be able to store waypoints, and give you bearing and
    distance to them, and cross-track error while navigating to a waypoint
    - in short, a basic (non-charting) receiver will do everything a
    chartplotter will do, except actually plot your position on a real
    chart. Most of the basic receivers do have a simple plot screen which
    will show your track and position relative to your stored waypoints.

    When I bought my Garmin 168 GPSMap/Sounder, charts were optional at
    extra cost, but I think some models now include at least some charts
    with the unit. Even if a plotter doesn't include detail charts of the
    area you are interested in, it will probably have a "base map" that
    will at least allow you to identify your position relative to the
    larger islands - it won't be adequate for any real navigation.
    In general, you have to but charts from the maker of your chartplotter
    - Lowrance charts can't be installed in a Garmin chartplotter, for
    I would expect that a unit that requires an external antenna would
    include an antenna in the base price. Likewise a unit that includes
    depth sounder capability should include some sort of depth/speed
    transducer - probably transom-mount, with through-hull transducers
    available at extra cost - again, see the maker's website, or a dealer,
    for accurate information.

    An internal antenna should be fine on the flybridge, even with a
    canvas top, but I would recommend an external antenna if the receiver
    is mounted in the cabin.
    You'd want to check on the availability of road maps, as opposed to
    nautical charts, for that application. There are many GPS receivers
    that are designed specifically for road navigation - they may omit
    some features (particularly cross-track error displays) that are
    useful in marine application, but include things like "lock-to-road",
    and audible or visual warning of impending turns, intersections or
    highway exits, which may be great on land, but are no use on the water
    (and won't be available in the marine units).
    Peter Bennett, VE7CEI
    peterbb4 (at)
    new newsgroup users info :
    GPS and NMEA info:
    Vancouver Power Squadron:
  3. I think your best buy for a chartplotter with built-in sounder is the Garmin
    GPSMap 498. Comes with transducer and antenna for about $850US. You can
    add a depthsounder and transducer to some Standard Horizon plotters, CP175c
    for example, but the total cost will be more. A simple handheld GPS will
    have some basic map built-in. This is likely to show lighthouses, bouys,
    etc. A plotter shows you an actual chart much like the paper version. I
    think most plotters now come with a complete set of US charts as NOAA has
    made these free to everyone.
  4. CGB

    CGB Guest

    Peter and Gordon,
    Thank you for the replies. I have gone with a Lowrance LMS 337C-DF. It is
    a leftover model from 2006. It comes with built-in GPS/sonar and also a
    separate transom mount transducer (double frequency), external antenna and
    various mounting brackets, separate speedometer pickup for the transom. On
    sale here in US, being a discontinued model I got it for $545 which seemed
    pretty reasonable. (There is little to no difference from this model and
    the one that replaced it for 2007 other than an Ethernet port in the newer

    Now as I've begun to learn there are a few things to add, like some SD
    portable drives at 2 Gig to download the software update (gotta download it
    onto an SD so it can be put into the gps unit so the gps can update its
    software). I don't have any 2 gig SD disks lying around so it looks like
    that could run a good $60 just to get a blank disk so I can do software
    updates on the machine! Then the actual maps/charts for higher res. (of
    course for the maps (not charts) you have to buy a proprietary SD disk card
    reader designed specifically and only for this software and gps unit just to
    transfer the higher res maps/charts from the CD/DVD into the gps unit).
    And, finally a power adapter so I can use it in my car. It doesn't seem to
    want to end. At any rate, I've taken the leap. And the icing on the cake
    is that there's no one at any of the marine shops around here who can demo
    any of the units, speak knowledgeably about them, have the high res
    maps/charts available to show them etc. Of course once you buy the detailed
    maps/charts, if you are unhappy, it's too bad because they ain't takin' them

    I looked at several brands, including Garmin, but concluded that they all
    pretty much have us over a barrel. There are a lot of after-market
    accessories to buy to get it looking like you think it should when you take
    it out of the box regardless of which brand I choose.

  5. Larry

    Larry Guest

    My Guaranteed-for-Life Ridata 4GB SD card was $53. 2GB cards are cheaper.

    Many items do not support the larger cards. (No laptops at CC will read a
    4GB SD card unless you steal a new driver for it from sagernotebook, for
    instance.) Call the GPS manufacturer and make SURE it will read a big 2GB
    SD card before you find out the hard way it won't.

    (Laptop owners: Follow the instructions from this Australian forum:
    The message at the top of the webpage gives detailed instructions on how to
    make laptop computers read an SD card bigger than 512KB because Micro$not
    uses a 2000/2002 driver for the TI multicard readers in laptops. Works

  6. Larry

    Larry Guest

    I see you've noticed NMEA's marketing strategy, too....

  7. CGB

    CGB Guest


    Lowrance tells me I must use a SD disk of at least 2 gig to download the
    update. As luck(?) would have it, COMPUSA had a $99.99 2 gig SanDisk SD
    disk on sale today for $34.99. I picked it up.

    When I downloaded the update from Lowrance and saved it on to the 2 gig SD
    so that I could then place it into the GPS, I noted the downloaded files
    were all of about 2 megs!! I'll try the update tomorrow and see if the gps
    unit recognizes it. And as per your comment about some machines can't
    recognize more than 1 gig (my HP digital camera can only recognize 256 MB),
    tech support at Lowrance told me the machine I bought would accept 2 gig
    SD's for mapping programs, etc. but can only recognize them as 1 gig.

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