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Old 04-30-2004, 01:32 AM   #1
marcucci
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Exclamation Why you shouldn't rely on GPS/Radar alone

I was just catching up on some posts and I notice people talking about GPS and I think there was one post about radar. However, no one said why you should not (or may not, should not is IMHO) rely on a GPS and/or radar to navigate winnipesaukee.

I have a handheld GPS in my boat that I loaded with some map software that gives me a ok map of the lake, however, there are many small islands missing. I also loaded Bizer's waypoint file on it and while it help it does not contain every single marker out there. I have heard stories of people using GPS to navigate the lake and ending up on a small island in their boat because they were just looking at the GPS screen. I have not used the C-map so I am not sure if that is any better. What I do is "track" my path (often to the eastern part of the lake) so I can follow it back and not pay as much attention to the markers. I never use it as my primary navigation device. I use my eyes and the charts (and my memory of the charts for the west half of the lake).

Now, about radar on the lake. I have been boating on the ocean but it wasn't my boat so I didn't know much about radar. I found out that radar has a "dead spot" around the boat of several feet and much further if the radar is up high. I was out one night watching fireworks in Meredith when a huge cruiser almost ran me and my wife down. My lights were working fine so I couldn't understand why the guy didn't see me. After he passed I noticed he was looking at a plotting screen and not out his window. I looked up and saw the radar on his bridge and realized I wasn't showing up on his radar and he would have plowed right through me! So the moral of the story, if you have radar, don't be this guy. Again, your eyes are invaluable for navigation!

This is my opinion...
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Old 04-30-2004, 07:43 AM   #2
hazelnut
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Default C-Map

Although I subscribe to your theory of not relying on my GPS entirley, the C-Map is dead on accurate. I have the Standard Horizon GPS with the BIZER C-Map cartridge and the thing has every single buoy/island/depth/marina/etc. etc. etc. It uses the actual map file from the Bizer printed map itself. I actually went to his house and bought it from him. Great Guy, by the way!

I have boated (day/night) winnipesaukee for almost twenty years. The first 18 or so with my eyes and a spotlight. I picked up the GPS as an added tool to navigate. In the past couple of years I have watched it carefully during the day to assess its accuracy. I have been extremely impressed. Every once in a while the display puts me a few feet + or - on the other side of a buoy. That is usually due to satellite issues etc.
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Old 04-30-2004, 09:31 AM   #3
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Default relying on GPS or Radar

GPS navigation, no matter how good the map the other boats aren't shown.
Radar navigation, can't see under water.

But that doesn't mean you don't want to have either or both. IMHO radar is too costly for a small lake boat, but GPS is within reason.
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Old 04-30-2004, 03:49 PM   #4
Coastal Laker
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Default Regarding radar

On the topic of radar...
Be aware of boats with their radar running while anchored or at dock near you. If you can actually see the array spinning (meaning it is not covered and you can see it twirling around) than you are getting zapped with radiation. Ask them politely to shut it down. It is not intended for long exposure use in close proximity like that. It is a long range navigation tool. It has settings designed to protect a range beneath it so passengers do not get harmed.

There are a number of regulations regarding the appropriate use of radar inland, only I don't remember all the details off hand. I just remember that the people using it need to be sure they are not exposing others to excessivlely long periods of short-range radiation. Perhaps someone can enlighten us more on this and let me know if I am off base here. I'll try and find supporting information when I have a chance.
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Old 04-30-2004, 06:12 PM   #5
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Default

Quote:
Originally Posted by marcucci
"...no one said why you should not rely on a GPS and/or radar to navigate winnipesaukee.
The archives indicated that in a time of national emergency, non-licensees (that's you) GPS' accuracy can go from 3-foot accuracy to 1000-feet.

Some folks who navigate ocean waters carry two GPS units. Things can go awfully wrong.

Quote:
I found out that radar has a "dead spot" around the boat of several feet and much further if the radar is up high.
1) That's true. CL is also right about the hazard to people of using radar at the dock. (You may be able to detect non-compliers by hearing "radar zap" noise on your radio).

2) Radar's reliability also diminishes in rough-water conditions.

Quote:
"...a huge cruiser almost ran me and my wife down.
Again, your eyes are invaluable for navigation!
With the increased installation/use of cellphones, stereos, DVDs, GPS, radar, VHF, and other distractions (like liquor) in today's boats, your eyes could very well save you.

I carry an old CD as a signaling mirror for sunny days and moderate seas -- when most collisions occur. It seems to help when in doubt on that approaching monster.

Boating has changed. You're right to be wary.


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Old 04-30-2004, 06:15 PM   #6
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Default

Coastal Laker,

Excellent point, I'm sure there are some that will say no harm but why take the risk. Marcucci also makes a great point. Staring at any instrument (or chart or newspaper)for more than a few seconds inside your boat underway while in command is dangerous and foolhardy even in fog or pitch black darkness.
Last summer I was in my sailboat when I noticed an older gentleman barrelling down on me with his head buried in a chart (I think or maybe he was cutting his fingernails). I watched him for what seemed to be a long time as I scrambled to get my canned air horn. Fortunately his better half noticed my 20+ foot sail right in front of her and pointed it out to her lesser half. He made a quick adjustment to my relief and passed with a sheepish look on his face. I keep that horn closer by now.

The point is there is no substitute for looking where you are going no matter what the conditions. GPS and Radar should suppliment your eyes looking beyond the bow for traffic and things you might hit. If you are doing it right, an occasional quick glance at these instruments should be all that is needed.
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Old 05-01-2004, 12:05 AM   #7
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Quote:
Originally Posted by Coastal Laker
On the topic of radar...
Be aware of boats with their radar running while anchored or at dock near you. If you can actually see the array spinning (meaning it is not covered and you can see it twirling around) than you are getting zapped with radiation. Ask them politely to shut it down. It is not intended for long exposure use in close proximity like that. It is a long range navigation tool. It has settings designed to protect a range beneath it so passengers do not get harmed.

There are a number of regulations regarding the appropriate use of radar inland, only I don't remember all the details off hand. I just remember that the people using it need to be sure they are not exposing others to excessivlely long periods of short-range radiation. Perhaps someone can enlighten us more on this and let me know if I am off base here. I'll try and find supporting information when I have a chance.
On a more serious note than my title ... people shouldn't be that concerned about some fools radar left running. This came up last year and I'll repeat what I said then. The microwave emissions from a marine radar can't cause genetic damage but can cook you same as a microwave, albeit a low powered one. I doubt a radar you'd see on Winni has enough power to burn you at the distance of a slip length but if you feel hot* then it's time to move. Your electronics are more at risk than you are. A radar shouldn't be emitting in or near dock and you should request the operator to shut it down but you shouldn't think like it' a bomb waiting to go off.

*I know a guy who worked on one of our military radars and would swear he could tell when the antenna was rotating because, in his operator's position, his ears would pop as the microwaves heated his inner ear. Never was sure if he was just yanking my chain ....

** I have been RF burned but that was when I put my finger tip across the open end of a co-ax cable carrying a fair amount of K-band power. It hurt for the millisecond I kept my finger there, but no lasting damage. I do believe the military is researching a microwave beam weapon, which by it's non-lethal action, encourages people to 'move away' in a manner like my finger was encouraged.

***Lastly the people in the radar equipped boat have some exposure to the RF emissions. They are "protected" by virtue of the antenna pattern which directs most of the energy outward rather than downward. Still if you could be seriously hurt by the RF by crawling out on the fore-deck, I'm sure someone would have sued by now and there'd be class action lawsuit shutting all marine radar down. This said I'd be cautious about wearing metal jewlery within a few feet of the antenna. Again think microwave oven re: this matter.
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