To All Who Responded. Thanks for your invaluable insight. It appears that I will be purchasing both a compass and GPS. Now does anyone have any suggestions on education/training material. Maybe the 'Idiots Guide to Finding Yourself with GPS' or 'Dead Reckoning for Dummies'. My compass experience stops with basic Boy Scout stuff and I have no knowledge of GPS systems. Maybe I should just stick to the inter coastal water ways during clear days with moderate wind??? Thanks again........I'm off to school!! Skip M-15 #201 -----Original Message----- From: Nebwest2@aol.com To: montgomery_boats@mailman.xmission.com Sent: Wed, 20 Dec 2006 7:52 PM Subject: M_Boats: Traditional Compass vs GPS I'd like to throw in a couple of comments on the GPS/compass discussion. If you are already versed in the differences between the two you already know what's typed below. If not, it might be of some help. I'm far from an expert on anything but between the boating, flying, and working for a store the sells GPS I feel fairly comfortable talking about them. You'll also read a fair amount of opinion below. I know not everyone agrees with my viewpoints on this stuff, but maybe it'll spark some interesting discussion (been kinda quiet around here!) . And I'll be in no way offended should someone feel like posting a contrary opinion. Heck, maybe you'll change my mind! Here's some points that I try to explain to folks when I'm working my part time job at West Marine and I'm helping someone with navigation and gps. One thing to keep in mind is that you really cannot "replace" a compass with a gps, unless the GPS unit you purchase also has a fluxgate compass integral in the unit. Garmin does make a few models that do actually have a compass incorporated into the GPS but most do not. The difference is this. A GPS really only does one function and derives all of the information it gives you based off of that one function. The one function is triangulation of your position on the face of the earth based upon 3 or more time signals received from the artificial constellation of gps sattelites that the good old USA put in the sky. It gives you that position in lat/long format or on fancier models it will actually display your position on an electronic rendition of a chart. Most modern GPS units recalculate you position at least once per second. If your position changes from the last position, the GPS compares the two positions and can tell what direction you must be moving to go from point "a" to point "b". It uses the amount of time that it took you to go from A to B , and the distance between the two to figure out your velocity and there you have it...everything else it tells you comes from that basic info. Here's the rub about replacing your compass with a GPS (or only having a gps on board)....Lets say you are walking straight north and have both a gps and a compass in your hand. Both will tell you that you are going straight north or 360 degrees. The gps knows it because it keeps comparing you previous and present positions and drawing an imaginary line between the two. The compass on the other hand knows that you are going 360 degrees because it is aligning itself to the earths magnetic field. Now, lets say that you stop, don't move your position any further over the ground, but instead you pivot 180 degrees while looking at both instruments. The compass will have remained aligned to the magnetic north pole and when you read it, it will indicate that you are facing 180 degrees. The GPS on the other hand will still indicate 360. Why? because it has no idea that you have pivoted around. Your lat/long has not changed, so it sees no change in your position and it cannot tell you are looking another direction. It will continue to indicate 360 until you actually change you position on the face of the earth by moving one direction or another. Therefore unless you are moving the GPS's heading or track feature is useless, whereas a compass will always indicate the direction you are pointed. This is not to poo poo GPS at all. Just to say that you can't replace a compass with a gps. A compass is neccessary for basic navigation for finding directions, landmarks, taking bearings to draw lines of position, etc. And, the GPS can do many functions that the compass can't. It is espeacially good at indicating the direction you are traveling over the ground (track) regardless of the heading of the boat. This makes compensating for crosswinds, set and drift, and things like that a piece of cake. I have a gps, love it, and wouldn't be without it. I use it extensively when boating, and when I was still flying for a living ( a very meager living it was! hahaha) I used them there as well. But you will never find an aircraft without a simple magnetic compass in the instrument panel. In fact, it is a required piece of equipment even on the jumbo jets. And in my opinion, you shouldn't find a boat without one either. I guess I'll finish my soapbox by saying that GPS is great. But please, if you are going to be in situations that are going to require navigation techniques to be used in order to keep you and your family safe, Learn how to do basic dead reckoning with paper chart and compass!!. Supplement it with GPS. Many folks are now venturing out into unfamiliar waters totaly dependant on their GPS unit. If the unit has a problem, their lost. What kind of problems? 1. Handheld GPS failure rates are astoundingly high 2. Batteries run out 3. It is extremely easy to transpose numbers when entering waypoints. Everyone does it sooner or later. If you are also using conventional navigation techniques while using your gps, and you make an error, things won't jive between the GPS and your figures and you'll know something is amiss before you reach Hawaii. 4. Although this is unlikely, the GPS system is a US military tool. They built it maintain it, use it(we paid for it), , and have the ability to shut it down at any time should they feel it necessary to do so in tha name of National Security. It would really stink if they turned it off while you were in that fog bank and you had nothing else going for you to tell you where you are. As far as where to mount a compass on a small boat. If you cant find a good spot for a fixed mount compass you might consider purchasing a quality hand bearing compass. They are about the size of a hockey puck and are great for taking bearings on landmarks to form lines of position. Just food for thought on a cold winter day. Hope everyone has their Christmas shopping done.!! Well, what do you think??? :-) Sean M23 Dauntless _______________________________________________ http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats ________________________________________________________________________ Check out the new AOL. Most comprehensive set of free safety and security tools, free access to millions of high-quality videos from across the web, free AOL Mail and more.