Jump to content

True vs Mag North and a stuck North Pointer in Map Mode


Recommended Posts

Yes....me again.

 

I'm learning more ever day but I've go more questions.

 

I went out with my GPSMAP 60CSx at lunch. I also carried my magnetic compass with me. On the compass page the north on the 60CSx is a few degrees west of my magnetic north. Why is this and which is more accurate? My 60CSx is set to TRUE NORTH.

 

Also, I have a weird problem. While walking in map mode, every once in a while my North pointer will seemingly get stuck. I can change direction 180 degrees and it will stay on the previous direction. Even weirder, I can always go to the compass page when this happens, stay still until the compass ring points north, the switch back to map mode and the north pointer is now oriented properly.

 

WTF?

 

I'm not sure I understand what's causing this. I can stand still in map mode and it won't change.

 

Any ideas?

 

Thanks again for your help.

 

Beck

Link to comment

Change GPSR to read Magnetic instead of True. Should then agree with your magnetic compass.

 

But which is the better choice? Do I necessarily want to change it to agree with my magnetic compass?

 

Thanks, Beck

They must agree to be accurate. True North is the location of the polar axis of the earth. Magnetic North is the location that a magnetic compass will point to. I live in San Diego, CA. If I were to walk North using a compass I would be heading towards the magnetic pole of the earth and miss the North pole by many miles. Do a Google search on this issue. They will explain it better than I can. A few diagrams will make the explanation clear.

Link to comment

The Magnetic North Pole is somewhere over Northern central Canada. Magnetic variation is the difference in degrees between True North and Magnetic North. The variation is different depending on where your position is. There is also Magnetic Deviation. No compass is perfect! Each compass has its own magnetic error built-in. Its usually just one or two degrees which isn't much, but if traveling long distances, it can throw you miles off course.

 

Unless you're navigating a ship or an airplane, or doing covert military ops, you're better off using True North.

Link to comment

 

Also, I have a weird problem. While walking in map mode, every once in a while my North pointer will seemingly get stuck. I can change direction 180 degrees and it will stay on the previous direction. Even weirder, I can always go to the compass page when this happens, stay still until the compass ring points north, the switch back to map mode and the north pointer is now oriented properly.

 

WTF?

 

I'm not sure I understand what's causing this. I can stand still in map mode and it won't change.

 

Any ideas?

 

Thanks again for your help.

 

Beck

Could be the transiftion to the magnetic compass is set to a rather long time. Go to main page/setup/heading and set the time and speed to something reflecting a person walking in the woods. Sometimes 3 mph, sometimes 1 mph, sometimes walking in circles. I think I have mine set to change to the magnetic compass when I go below 2 mph for more than 15 seconds.

Link to comment

Which is better really depends on how you are using the GPS. If I were using the GPS with a compass, but without a map, I would probably set the GPS to magnetic north. If, however, I were adding a map to the mix, I would set the GPS to true north and also set the declination angle on the compass, i.e. the location-specifici discrepancy between magnetic north and grid north (assuming you have a compass with that feature). That way the map, compass and GPS would all show the same north.

Link to comment

 

Also, I have a weird problem. While walking in map mode, every once in a while my North pointer will seemingly get stuck. I can change direction 180 degrees and it will stay on the previous direction. Even weirder, I can always go to the compass page when this happens, stay still until the compass ring points north, the switch back to map mode and the north pointer is now oriented properly.

 

WTF?

 

I'm not sure I understand what's causing this. I can stand still in map mode and it won't change.

 

Any ideas?

 

Thanks again for your help.

 

Beck

Could be the transiftion to the magnetic compass is set to a rather long time. Go to main page/setup/heading and set the time and speed to something reflecting a person walking in the woods. Sometimes 3 mph, sometimes 1 mph, sometimes walking in circles. I think I have mine set to change to the magnetic compass when I go below 2 mph for more than 15 seconds.

 

Klatch,

 

I've already changed the time to 3 mph and 15 seconds. The compass does indeed respond to that quickly.

 

The problem is the north pointer in map mode. It's the one getting stuck. And it will stay stuck until I go to the compass page, then back to the map page.

 

Any ideas?

 

Thanks, Beck

Link to comment

 

 

Klatch,

 

I've already changed the time to 3 mph and 15 seconds. The compass does indeed respond to that quickly.

 

The problem is the north pointer in map mode. It's the one getting stuck. And it will stay stuck until I go to the compass page, then back to the map page.

 

Any ideas?

 

Thanks, Beck

Sorry, I have not experienced that. I am assuming you have the latest software updates installed.

Link to comment

Also, the GPS must be held VERY close to level, and not close to belt buckles, or your magnetic compass or anything else metal...to be accurate.

 

Do an experiment.....calibrate your GPS compass and lay it flat on the floor. Now lay your magnetic compass on the floor right next to it. Neither will read correctly until they are separated by about a foot.

 

If your magnetic compass has a declination adjustment, set that for the correct declination for your area and then it will read the same (point the same direction) as your GPS when that is set to True North

Link to comment

First off,does your compass have an ajustable declination scale on it? If so then set it to the correct declination,the compass needle will now point to TRUE north ,but also you will no longer have to do the math every time you transfer a bearing from the map to the field or vice-versa.Now set your GPS to display TRUE north,and make sure every time you use your GPS to calibrate the compass.Now when your compass points north it is far easier to orientate your map to TRUE north.

If your compass does not have an ajustable declination scale you will have to calculate your field and map bearings every time .If this is the case set your GPS to MAGNETIC to match your hand held and align your map to MAGNETIC North.My compass on my 76csx which is the same as your compass is not that good,it has an acurracy of about +/- 5 deg.You can see this if you do a sight-n-go.Then move around ,then come back to where you were originally standing and the compass is pointing off a fair bit.A good hand held compass rarely lies.Get a Suunto,Brunton or Silva mirrored sighting compass with ajustable declination and always carry it and a proper topo paper map with your GPS.

Link to comment

Yes....me again.

 

I'm learning more ever day but I've go more questions.

 

I went out with my GPSMAP 60CSx at lunch. I also carried my magnetic compass with me. On the compass page the north on the 60CSx is a few degrees west of my magnetic north. Why is this and which is more accurate? My 60CSx is set to TRUE NORTH.

 

Also, I have a weird problem. While walking in map mode, every once in a while my North pointer will seemingly get stuck. I can change direction 180 degrees and it will stay on the previous direction. Even weirder, I can always go to the compass page when this happens, stay still until the compass ring points north, the switch back to map mode and the north pointer is now oriented properly.

 

WTF?

 

I'm not sure I understand what's causing this. I can stand still in map mode and it won't change.

 

Any ideas?

 

Thanks again for your help.

 

Beck

Link to comment

You can try here to check your declination, bear in mind the amount declination changes from year to year

http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp

You can enter your coordinates (in decimal format) or enter your zip code in the box provided.

Do an experiment.....calibrate your GPS compass and lay it flat on the floor. Now lay your magnetic compass on the floor right next to it. Neither will read correctly until they are separated by about a foot.

Maybe not a real good idea, most houses use wooden floors and wooden floor joists, and nails (steel) to hold it all together, try a large flat surface such as a table that has been glued together, or a large cardboard box placed on the floor, about a foot above the floor should work better, watch out for staples.

 

This reminds me of a story, when I got my first GPSr. a Magellan Sportrack, I started out wanting a good compass, don't remember why anymore, I exchanged the Sportrack for my Meridian about a week later, the Meridian had more bells and whistles. The compass I have is a army surplus unit I got about 20 years ago, it is scaled in mils, and degrees but the degrees are only graduated every 5 degrees so I don't use it much anymore. FYI there are 3200 mils in 360 degrees, yes my meridian will use mils also, not much use in the civilian world.

Edited by earthshaker
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...