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Two Dumb Questions


Doc43

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I am new to the game, and I have been using a Cobra 500. On the gauges page, I have a bearing and an arrow on a dial that points in a different direction than the bearing. What am I missing here?

 

Also, what is the difference between a "bearing" and a "course"?

 

Many thanks...

 

Doc

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Course:

 

"A course, in navigation, is the direction of travel.

 

The term, even in navigation, can be ambiguous because there are several types of course:

 

course is the general term describing the bearing to be followed to move from the destination to a particular target

heading is the direction the vessel or vehicle is pointing toward - it may be necessary to point away from the intended course to counteract the effects of a cross wind or tidal current or some other force

track is the actual direction of travel irrespective of the heading"

 

Bearing:

 

"In navigation, a bearing is the angle between the direction to an object and a reference direction. Unless otherwise specified, the reference direction is generally understood to be magnetic North, in which case the term compass bearing is also used. If navigating by gyrocompass, the reference direction is true north. In stellar navigation, the reference direction is that of the North Star, Polaris.

 

Generalising this to two angular dimensions, a bearing is the combination of antenna azimuth and elevation required to point (aim) an antenna at a spacecraft. The bearing for geostationary satellites is constant. The bearing for polar-orbiting satellites varies continuously.

 

Moving from A to B along a great circle can be considered as always going in the same direction (the direction of :), but not in the sense of keeping the same bearing, which applies when following a rhumb line.

 

Accordingly, the direction at A of B, expressed as a bearing, is not in general the opposite of the direction at B of A.

 

For example, A and B on the northern hemisphere have the same latitude, and at A the direction to B is eastnortheast. Then going from A to B, one arrives at B with the direction eastsoutheast, and conversely, the direction at B of A is westnorthwest."

 

You're most welcome!! :D:):D:):D

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Lets just say you have no obstructions between you and the cache, in a giant cornfield or something like that. your gps says it's 400 meters (or feet, whichever measurement you are used to) straight ahead. So you walk straight ahead, accross the open area. Now look at the gps. The bearing and course (sometimes called heading) both say the same degrees. Now imagine you walk straight up to a river, and the only way to cross it, is to turn away from your current direction of travel to get to a bridge 100 meters (or feet) down river. As you walk down river, look at the bearing and course (heading). the bearing is representing the direction to go to get to the cache, but the course (heading) is telling you the direction you are now traveling in.

In short, if your bearing and course (heading) are exactly the same, then you are headed in a straight line to the destination, the cache.

 

Hope I didn't confuse you. :o:(:D

Edited by ashleedawg
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Bearing is the direction from your cuirrent location to the final destination.

Course is the direction from your starting location to the final location.

 

Couurse and bearing start out the same when you hit "go to". Then Bearing changes as you move around -that's why the arrow will point to different degrees on the compass rose. However, course will always remain the same. If you started out at 65 degrees to the final destination, even if you walk arouind in circles, the course direction, will remain 65 degrees until the next "go to" is commanded.

 

Check that on your GPS - switch between course and bearing and watch what happens to the arrow.

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Bearing is the direction from your cuirrent location to the final destination.

Course is the direction from your starting location to the final location.

 

Couurse and bearing start out the same when you hit "go to". Then Bearing changes as you move around -that's why the arrow will point to different degrees on the compass rose. However, course will always remain the same. If you started out at 65 degrees to the final destination, even if you walk arouind in circles, the course direction, will remain 65 degrees until the next "go to" is commanded.

 

Check that on your GPS - switch between course and bearing and watch what happens to the arrow.

 

It sounds like my assumption that course and heading were the same thing is incorrect. Sorry.

 

My magellan doesn't have course on it, but it does have a heading. And it behaves like I described above. previously.

 

But I have a question? What would be the purpose of having a field that tells you what direction you should've gone in when yer not there anymore?

Edited by ashleedawg
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I'm not an expert. Not sure what the difference between course and heading.

 

Regarding why you want to know the course degrees after you have gone a while is not clear in my mind either. I always use bearing. However, I believe course is helpful to sailors to have a boat that tacks laft and right. They may wish to always know the "course" they want to get back on rather than the most direct route or "bearing".

 

Also, let's say you are heading for a mountain which is 6 miles away but you have not set a waypoint. So off you go let's say at 135 degrees. Pretty soon you run into a lake that you can't walk across. So you work your way around the lake and when you're on the other side you pick up the course degrees again 135 and start heading toward the mountain.

 

At least that's how I understand it. Maybe someone else can better explain when to use course and not bearing. Any sailors out there?

Edited by Alan2
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I'm not an expert. Not sure what the difference between course and heading.

 

Regarding why you want to know the course degrees after you have gone a while is not clear in my mind either. I always use bearing. However, I believe course is helpful to sailors to have a boat that tacks laft and right. They may wish to always know the "course" they want to get back on rather than the most direct route or "bearing".

 

Also, let's say you are heading for a mountain which is 6 miles away but you have not set a waypoint. So off you go let's say at 135 degrees. Pretty soon you run into a lake that you can't walk across. So you work your way around the lake and when you're on the other side you pick up the course degrees again 135 and start heading toward the mountain.

 

At least that's how I understand it. Maybe someone else can better explain when to use course and not bearing. Any sailors out there?

 

Sounds like a good case and point to me. Thanx!! :ph34r:

Edited by ashleedawg
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On my Garmin GPSMAP 60c, the compass works like this:

 

The direction I am currently moving is always the top of the screen and the compass rose moves to indicate what direction that is relative to North (I believe there are a couple of options to determine what it uses to determine which way is north whether magnetic or true north).

 

The bearing needle always points to the target.

 

The course needle always points to the direction the target was when you started out.

 

There is also a course deviation indicator which lets you know how much you drifted off your course so you can correct it.

 

I have never use the course needle, because as was alluded to earlier, it is primarily for marine navigation where you want to maintain some sort of straight line, but yet have to deal with shifting currents etc or maybe tacking to make use of the wind.

 

joe

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