Moderated Discussion Areas
  ContinuousWave: Whaler Performance
  GPS Screen Size

Post New Topic  Post Reply
search | FAQ | profile | register | author help

Author Topic:   GPS Screen Size
mustang7nh posted 12-17-2003 06:57 PM ET (US)   Profile for mustang7nh   Send Email to mustang7nh  
I read the discussion about the Garmin 76S and appreciate its strong qualities for a handheld but also realized the comments about it being pretty hard to navigate by while underway in some choppy water.

Any suggestions on the minimum screen size that one can reasonably use to navigate?

On a cc are the internal antennas fine in terms of reception?


triblet posted 12-17-2003 08:49 PM ET (US)     Profile for triblet  Send Email to triblet     
I used to have a Garmin 175, and it had better signal strength
with an external antenna mounted on the console rail than
it did with the built-in antenna under the console rail. It
worked with the internal antenna, but when I bought a 162, I
got the external antenna version, and mounted the antenna on
top of the rail.


doobee posted 12-17-2003 11:22 PM ET (US)     Profile for doobee  Send Email to doobee     
On a small screen like the Map 76, I use the chart for plotting at the dock, then I use the steering indicators, which are very easy to read while underway.

The Garmin 180/182/188 series is about the smallest chart you would want to use underway. Also the most bang for the buck. The Raymarine 425 is very similar to the Garmin, and the Standar CP160 isn't bad either.

In all cases, color is definately the best choice.

Moe posted 12-17-2003 11:35 PM ET (US)     Profile for Moe  Send Email to Moe     
Agree with doobee's comments. Also, Lowrance is bringing a bunch of new units this Spring, and from what I've heard, they'll be a lot lower priced than the Garmin units. I still like Garmin's interface better though.
Peter posted 12-18-2003 06:57 AM ET (US)     Profile for Peter  Send Email to Peter     
I used to use a Garmin 175 on an 18 Outrage and then a 22 Revenge mounted in the swivel mount and its screen size was quite adequate in both applications. I now have the portable Garmin 176C and the fixed mount 182C. The 176C screen size is about the same as the 175 and should be sufficient for navigation provided you can mount the unit close to the helm. If you have room and want a permanent mount instead of a portable, the Garmin 182C is quite a nice unit. I agree with Doobee, go for the color, its definitely worth it.

mustang7nh posted 12-18-2003 01:03 PM ET (US)     Profile for mustang7nh  Send Email to mustang7nh     
Does Garmin have a PC interface for the handhelds like the 76 that you could do you plotting at home, download, and then use the steering indicators while underway?
BW23 posted 12-18-2003 01:27 PM ET (US)     Profile for BW23  Send Email to BW23     
The 76MAP includes a PC interface cable.
You will also have to purchase the BlueChart CD, and download the regions that you will be navigating.

I have the BlueChart Data card for my region.


Sammy posted 12-19-2003 12:25 AM ET (US)     Profile for Sammy  Send Email to Sammy     
To follow up on the comments by doobee and Moe, I think you're better off with a quality compass and a good set of charts for primary navigation equipment - using GPS map gear for occasional reference/confirmation - especially in choppy conditions. It always seems that the gremlims pop up (or the batteries die) in electronic equipment at the worst possible time.

On our 25 foot (not a Whaler), the enclosed electronics compartment at the helm allowed enough room for a fixed mount Lowarance LMS 160 Map. The screen on that unit is approximately 3.25 x 3.25 inches, or a little over 4.5 inches measured diagonally. That has worked out well for back up - but not primary - reference.

I wouldn't want to depend on a handheld unit for primary navigation reference in snotty conditions - even though there are some great little units on the market.

arnereil posted 12-19-2003 08:18 AM ET (US)     Profile for arnereil  Send Email to arnereil     
I have a sport 13 and charts are a pain. Since it is a small boat, handling a chart is difficult (and not much storage space).. so have more or less decided to get a garmin 176c... It is a bit too big to be a hand held, but is small enough to sit on my diminutive console top with a friction mount.... and it can be used on other vehicles I own.. kind of an affordable mid-sized screen with good reviews.. The battery life is a 'con' in the reviews, but most of the time it will use the boat/vehicle power supply...
Moe posted 12-19-2003 11:55 AM ET (US)     Profile for Moe  Send Email to Moe     
I certainly agree that a quality compass and charts are essential, as is knowing how to use them (i.e. having actually used them in practice), but I wouldn't put them in a primary role any more than I'd use rope start as the primary method of motor starting.

Programming tracks can be done either on the GPS unit itself, or on a PC with the appropriate software and cable.

The problem with doing so, on a non-charting GPS, or on a handheld where the chart is too small to read in the motion of seas, is that you can't always stick to the track.

A good example of this is coming up on a bunch of boats anchored right in the middle of your track. If you've programmed it to avoid a shoal or hazard, you now have to remember on which side of the track is the hazard, which attracted all the fish, that brought these boats here. A chartplotter you can read while underway will show you where the shoal or hazard is.

People "think" differently when using a chartplotter. Those who think when boating the same as they do when driving, may prefer to view the chart in a "track up" orientation, where objects on the chart are to the same side as they are relative to the boat's track. Those who are used to navigating on a chart or map, may prefer to view the chart in a "north up" orientation. Regardless of the orientation of the display, most GPS chartplotters give you a choice between "track up" and "north up."

When using the "track up" (rather than "north up") option, a portrait display (taller than wide), shows you more of your track to come at a given zoom level. A landscape display (wider than tall) would show you more if you were on an east/west course using "north up" orientation. Regardless of orientation, these displays are typically 75% aspect ratio, meaning one dimension is 75% of the other. This makes the height/width and diagonal a 3:4:5 right triangle, so it's easy to compare different diagonally sized units.

The orientation of the display is probably more significant when it's combined with a fishfinder, and a split display is used in lieu of separate displays. A portrait display can use 1/4 of its vertical height for the fishfinder, and leave a "square" area for the chart. While this may be adequate for shallow areas, such as western Lake Erie, it gives poor discriminiation in deeper water. For this, the landscape display can use 1/4 of its horizontal width for the fishfinder, spreading the depth over a much taller display area with better discrimination.

To answer the question, I'd feel, that in chop, a minimum of a 5" diagonal portrait display (i.e. 4" in the vertical dimension) is good. A 6-7" (+/- 4" on the short side) would be considerably nicer, but a lot more expensive.

Sammy posted 12-19-2003 02:37 PM ET (US)     Profile for Sammy  Send Email to Sammy     
Excellent points on the importance of knowing how to use a compass and NOAA charts as well as using them in practice - especially while underway. That can become more important depending on the waterway. I also think you're estimate of the minimum screen size is definitely in the ballpark. But when serious navigation is required for recreational boaters, it goes beyond GPS.

We fish lake trout off of Isle Royale 1-4 times a year. It's 20-plus miles across Lake Superior from our launch point at Grand Portage, MN, to Washinton Harbor on the southwest tip of the island. It's another 40-plus miles to Rock Harbor on the northeast end. It's an even longer trip for those launching from Houghton, MI.

There are several points around the island where depths change dramatically and dangerously - and it's all granite. With water temps running from the low 40s to upper 50s in the middle of the summer, it can be a very unforgiving lake for experienced commercial captians let alone unprepared, careless, wreckless or not-very-bright recreational boaters. (Why would you wear a wear life jacket while underway on Lake Superior? Because it's easier for the S&R crews to find the body.)

The benefit of a paper chart is it allows the navigator to get a complete navigation picture plus the ability to quickly focus on specific details - then quickly refocusing on the water or surrounding landmarks/boats. NOAA charts also have depth soundings that are usually not available on handheld GPS units.

I wouldn't be without my GPS Map equipment - it's great for logging routes, fishing spots, keeping track of exact time, speed and distance traveled and comparing it to estimates, etc. But I use it mostly for reference and confirmation when I can safely take my eyes off the water ahead for an extra few moments. If that means slowing down for a moment, so be it. Incorporating it as part of your navigation equipment can also improve compass, chart and dead reckoning skills.

I'm not saying GPS should be avoided or that it's no good. Just the opposite - it is a valuable tool. If cruising warm coastal waters in sight of land or on small lakes or rivers that are somewhat familiar, then using a GPS Map unit is as much fun as it is serious navigation. The original question was what is the minimum handheld GPS screen size for navigation while underway - but most GPS manufacturers warn not to use their stuff as primary equipment for navigation.

triblet posted 12-19-2003 08:30 PM ET (US)     Profile for triblet  Send Email to triblet     
All the depth soundings on the NOAA charts are on the Garmin
BlueCharts, which can be loaded into their charting handhelds.

I have a GARMIN 162, 4.2" diagonal, and it's big enough. I
boat on the Pacific Ocean and it can get choppy. One thing
that's important is to configure the chart screen to include
a track direction arrow, so you know which way it is to the
next waypoint without switching screens. A bigger screen
would be nice, but it's more money, and more importantly,
more console space.


jimh posted 12-20-2003 12:47 AM ET (US)     Profile for jimh  Send Email to jimh     
[Administrative post]
CHRISWEIGHT posted 12-20-2003 03:16 PM ET (US)     Profile for CHRISWEIGHT  Send Email to CHRISWEIGHT     
I use gps to mark fishing spots and also for marking hazards on the way back to home base for which I have set up routes dependent on our direction of approach, very usfull in fog.

I have a garmin 126 which is fine for size in reasonable conditions although making any adjustments can be tricky in anything other than a small chop. in my view a small hand held could be very difficult.

I use paper charts which I scan onto the PC and print the areas we cruise in colour and then laminate them as A4 sheets, these are easy to read in a small boat and waterproof giving good level of detail.

MnFast posted 12-29-2003 10:48 AM ET (US)     Profile for MnFast  Send Email to MnFast     
I use a Garmin 175 with an external antenna and the portability of it enables me to carry it to any boat. The screen size is quite adequate for use on my Montauk in choppy waters (have it on a Garmin mount and it stays in place). This 175 is no longer made by Garmin and I understand that the G-charts for inifinite detail will no longer be supported by Garmin (so 175 users, get your G-charts now while still available). I am a big Garmin fan and any other hand held that has a similar screen size will be adequate for small boat use in choppy waters. With the right software you can use it with a PC as well. Garmin has a program, but they admit it is not as good as some of the other popular map pc programs available on the market.
I have navigated thousands of miles with my 175 in the Great Lakes, Florida, the Bahamas, etc. and it is wonderful.
JBCornwell posted 12-29-2003 01:43 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
I only fish inland lakes, but most of them are very large and have many, many islands and inlets as well as many hazards. Without GPS it is very easy to get lost or land on unmarked rocks on Lake Of The Woods.

I use charts and my PC to plan my day on the water and my Garmin 162 to tell me about where I am. I am very conscious of the warning displayed at turn-on that the instrument is NOT for navigation, but reference only.

Size? If I had room on the console I would mount an inexpensive laptop there to display what the 162 is doing. Lots cheaper and lots more memory than even the Garmin 2010C. I just haven't figured out how to make it waterproof and fit it onto my console.:))

Red sky at night. . .

JohnJ80 posted 12-31-2003 05:15 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
I agree with much of what Moe and Sammy are saying.

My frame of reference is that I have navigated all over Lake Superior (mostly) and a lot in Lake Michigan as well as Ocean offshore. In point of fact, I have successfully navigated between the three rock piles (no straight path through) on the southern edge of Isle Royal during races from Thunder Bay to Marquette to save distance and in bad weather. There is not much that is hairier in navigation than that.

You NEVER have a single navigational method and you ALWAYS keep a dead reckoning plot.

That all being said, the paper charts, dividers etc... are secondary tools now in the age of GPS. I always plot my course before I leave the dock, make sure all the way points are entered properly into all of the navigational tools and marked on the chart.

Then as I move down my route, I record on waterproof paper every 15 minutes my last position, speed and heading in case I have to make an emergency mayday call.

My primary nav tools are now the GPS. At the cost of GPS, it is no big deal to buy two disimiliar units (so that there are not common software errors) and a backup for each as handhelds. For example, I would buy a Garmin console mount plotter and have a garmin handheld and a magellan handheld as backup. I would also keep 8 AAs in a waterproof bag in my gear bag - or enough to power a handheld for the expected duration of my passage plus 50% (remember, you can always turn them off and then keep a DR plot between GPS 'fixes').

This setup would get you through most everything out there and the risk of ALL of these things failing are vanishingly small. Even if they did, I still would have my DR plot to get me back or home. However, I wouldn't go to this until the very last.

Just last week I was sailing in the BVI. We were headed for Anegada (a 20' high island completely surrounded by reefs). There is only a very, very narrow entrance and it is shoal water on both sides. Not a lot of visual landmarks if the weather is bad.

Now, paranoid naviguesser that I am, we started off from a point about 12 miles away in sunlight with just a small caribbean shower in sight. After we were almost there, the thing turned into a full out tropical wave with pouring rain and about 100 yard visibility.

I had my usual DR plot going but with my laptop with the BSB charts running connected to my GPS 12 MAP (Garmin), I was able to slowly motor up to the very narrow channel and precisely eyeball the channel marks (entrance) while monitoring depth and compass heading. If I had had to rely purely on DR or paper charts, no way could I have gotten that level of precision. I would either have had to lay off and wait for the weather to clear or to abort the attempt entirely.

So, I think you can rely on the technology as a primary - and probably should - with backup on both paper and handheld. But I definitely would not use paper as my primary source of navigation. While electronics can fail, so can paper in a very wet environment (been there, done that, got the T-shirt). Not a lot of fun trying to get a plot on scraps of a soaked chart.

Looking at one of the garmin waterproof units (handheld) - they are built like a tank. The probability of one of these failing is pretty doggone small. You would get more error and danger out of crinkles in your chart or in the risk of a chart being inadvertently destroyed or blown overboard (I've had both happen). So, nothing is failsafe, the trick is to have enough dissimiliar backups.

Just my $0.02.


WSTEFFENS posted 01-06-2004 12:01 PM ET (US)     Profile for WSTEFFENS  Send Email to WSTEFFENS     

For what its worth. I have a 25' W/T that I use primarly on lake Huron in the North Channel. When I replaced my old Micrologic Loran with a GPS I again went for a hand held that was water proof and would float. What I purchased was a Magellan Nav 6000. The reasons were the following. The hand held doesn't need the boats electrictal system, this may seem trivial, however older outboards charging systems usually don't put out much and the redundency is a vlaue to me. Water proof, as the helm and navagation station can get wet even with the canvas up under bad conditions, or even on sunny days in large water. Hand held, as I have the ability to move the unit from the helm position to the chart area without having to move a bracket or mount to be able to reference the chart to the display. The display on the Nav is 2.5w x 3.0h. One thing I would definately look for is a unit with the display up top and the key pad below, as this allows you to use the keys without loosing sight of the display; seems trivial but when things get fast and hairy it is worth it.

As mentioned above, the GPS isn't a replacement for good charts. The detail on my unit isn't any where close to the detail on a Richardson chart book.

Good electronics hunting!


Post New Topic  Post Reply
Hop to:

Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.