GPS direction changing when not holding level?

[311Hemi]

Just curious why my GPS reads correctly when I have it sitting flat on the floor of the boat, but when I hold it more verticle it changes direction (I think 180*).

Anyone else have this problem or know what I am doing wrong. My buddy has the same issue. Whenever we put the GPS in a mount holding it verticle it does not point the direction we are going.

Both newer Garmin....mines a 60CS.

[Giant_Jackpot]

Are you motionless when this happens? A GPS does not know what direction you are pointed unless you are moving.

[311Hemi]

With an electronic compass it should, right?.

And yes, this is mainly when trolling, so around 1mph give or take a little. Would need to check higher speeds.

I think I need to get and external entenna that will mount to the boat flat, as I think the GPS needs to either be held flat or moving at a decent rate for the compass to work properly and thus orientate my screen properly with the boats direction.

It's just that my initial thoughts are that many people mount the GPS to the boat in more of a verticle position (on/near the steering console). And then from there use the GPS figuring that since the GPS is mounted the way the front of the boat is pointing that is what will show on the screen (for troling over way points or following a particular line). I am guessing many people have this issue or use external antenna, or just keep it laying a little flatter?

[BobT]

I don't know how those electronic compasses work but if you hold it vertical, how does it know which way you are facing? My guess is that an electronic compass must have a point of reference regarding the direction the gps unit is oriented.

Bob

[Bob O]

Can't tell from your post what you mean by "it changes direction". Unless it says "position lost" or something like that, the GPS knows which way is North, etc. However, when sitting still or moving very slowly, it may not know which way it is moving or pointing, so the pointer may switch directions from moment to moment. That's because the satellite signals have some random error of several feet in any direction.

If the whole screen is changing directions (not just the pointer), then you may find it helpful to change the settings. My old Lowrance has a setting to keep N at the top of the screen, which I find a lot less confusing than having it try to keep sync with the pointer which indicates direction of travel.

To get a better feel for the random signal effect, stand on land, set a GPS waypoint, walk away from it, and set the unit to tell you how far you are from the waypoint. Walk back to your spot and watch the screen for awhile. The distance indicator will keep changing as if you are moving.

The unit does not use a compass. It triangulates locaton from 3 satellites (and a 4th satellite for altitude). Whether the unit is flat or vertical does not make any difference. An antenna might be helpful if it is mounted high enough to help it hold to the same three satellites. As you turn around, obstructions (such as your body) cause the unit to switch satellites. It is always monitoring 12 satellites and picking the best three for positioning. But I would get more familiar with the GPS settings and practice with it before spending money on an external antenna.

[Gus]

I have an Etrex Vista that will do the same thing. It also has the built in compas. I do two things that lessen the issue. 1. I set the map to always face North. 2nd I set the GPS to use gps heading when above 1 or 3mph and (1 for slower activities, 3 for moderate activities) and to use compas when below 1 or 3 mph (whatever one corresponds). These two, in most cases, will solve the problem. If that doesn't do it, have you tried playing around with the calabrate compas feature? I do this to mine every so often. All you really do is hold the unit level and spin it around slowly 2 or 3 times until it tells you ok. Since it tells you that you need to hold it level, I do believe that holding it verticle or semi verticle will mess with the built in compas. Which is why I like to have the heading tell me direction when at all possible. One other thing, when I set it to read from compas below 1 or 3mph I usually add the "when below for 30 seconds" or something simialr. If you are in the menu items you'll be able to tell what I'm talking about better than I can type it.

[DTro]

Perhaps the compass is trying to lead you to "The Dead Man's Chest".

Sorry, having seen the movie yesterday, I couldn't resist.

[311Hemi]

Well, I guess what I am trying to explain is that the electronic compass (which I understand triangulates off satellites) works properly when holding the GPS flat. I.E. if I am in one position and turn the compass the compass is accurate (while holding the GPS flat). If I stand facing north with the GPS flat is points north, but if I lift the GPS up in front of my face so it's at say a 45* angle it no longer points north but south I beleive. Just trying to figure out if anyone else has this problem when using the electronic compass. It does not require the user to be moving. Must be with how the antenna is laid out in the unit.

I like haviing the GPS set so the pointer indicates direction the gps is facing, but maybe I will just have to try some different settings and get used to it.

Gus, I will have to try the always point north setting, but I would prefer to have the GPS pointing in the direction I am traveling. I could probably get used to the other way however, just need to try it.

I also calibrate compass, but that does not affect the reading when hold it at and angle in front of you. I am thinking the antenna does not cordinate the satellite properly when held verticle, and thats why I was thinking about getting an antenna to mount flat, so I can use it the way I like.

Looks like I will have to play around with it this weekend on Mille Lacs.....and maybe read the manual!

This could all be user error also.....I am guessing it should not work when totally verticle, but at a 45* it should.

[Gus]

Let me know how it goes for you this weekend. Cardinal directions and me do not get along well. I also prefer to have the way I'm moving be up, but I've also had the same wandering compas problem. The only way I know of to get it to hold more steady is to have north up and rely less on the internal compas and more on satelite movement.

Now that I'm used to the way it operates it really isn't that bad to deal with. I figure when I'm on the lake, I'm usually moving anyway so I let the satelites tell me which way I'm going. If I'm off lost in the woods scratching my head, I like having the internal compas just tell me which way to walk (but you have to hold it level for that). To me having that compas is much better than starting to walk through the woods and then have the gps tell me I'm heading in the wrong direction once I get moving.

[311Hemi]

Cool, will do Gus. I will give it a shot this weekend to see what I think.

BTW, you ever get that snowblower running?

[Macgyver55]

I don't know what model you have, but my Garmin GPSmap76S has the compass and it must be held level to be accurate when stopped. It also has a small note box that pops up and says "hold level" to tell you when its not. You'll probably find if you read the manual yours operates in the similar manner.

Also, having the screen set to "north up" (like all maps are printed) will show right away what direction you are heading on the map when you are moving.

[Gus]

Never did make much of an attempt at that snowblower yet. I've got a mower that I need to get running now as well. My bro in law is good at small engines so I'll probably take them both over to his place this fall. Later.

Gus