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GPS- Dumb ?"s


Toadily!

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When I go to the compass page on my GPS, shouldn't it know which way is North? Today it thought N was South for quite a long time before it finally got it right. And I had excellent satellite coverage & had turned it on several minutes beforehand.

Also, I assume that after selecting a waypoint already downloaded into the GPS, that I should be able to just follow the arrow on the compass page to or very close to the item. . . but the arrow jumps ALOT as I get close.

Are these things normal? Or is my GPS screwed-up? It's a Garmin 12 XL, but at least 4 yrs. old. Are the new ones more accurate?

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It depends on the GPS you have. Unless your GPS has an electrronic magnetic compass built into it does not know which way you are holding it. If it does have an electronic compass it still needs to be calibrated. I have three GPS'rs with Triaxial compass but I do not bother with using the compass so none of mine are calibrated. In the early years of geocaching there was no such thing as a magnetic compass in a GPS. Once a cacher would walk a few feet the GPS would compass screen would work. As far as the arrow jumping around a lot at ground zero, that is normal. Keep in mind that GPS'rs that we use are going to be accurate to about 9 feet on average. Once your are within 10 or 15 feet just start looking.

 

The Garmin 12 XL is older technology that dates back more than 4 years, I was selling those before I retired and I have been retired for a long time. I would put the accuracy on that unit at about 15-20 feet.

 

I found this Data re. the Garmin 12 XL regarding updates that have been made, the most current update Was in Dec. 2001. I retired about nine years ago. I was a GPS buyer for a small chain of stored in N.Ca. I think A stoped ordering the 12XL soon after around 1999. Garmin tends to keep products in their product line for a very long time

 

Revision 2/2/97 - (see mountain performance & antenna connector, ... )

Revision 2/7/97 - (Ext. Ant, Current Draw, Dead Reckoning, Data Smoothing, ... )

Revision 6/29/98-(New hardware platform, CityPoint database)

Revision 3/8/99 - (Incorporate G-12CX Color GPS feature differences)

Revision 3/28/99-(Review by Bob Kaemmerer)

Revision 12/23/01-(Ver. 4.57 adds area-calculation feature)

Edited by JohnnyVegas
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Your GPS does not know which way is north, or which way it is facing when you're holding it. It only knows its location relative to the array of satellites overhead. So in order for it to determine a direction you need to be moving...it calculates the direction in which you are moving through multiple, constant updates of your current location. Fortunately you don't really need to be moving very fast or very far for it to get a fix on your direction...just take 3 or 4 steps at normal walking speed and it will figure it out.

 

You stop moving and turn around in one spot, the GPS will start acting funny because it doesn't know you're turning, only that you've stopped moving. It will probably still show your direction relative to the last direction you were moving.

 

Newer units with a built-in electronic compass WILL know which way you are facing, and which way is North, regardless of movement. But like Johnny said they need to be calibrated occassionally. I don't have one but I've read that some units will prompt a calibration every time you change the batteries.

 

Don't think of the "compass" function on your GPS as an actual compass. It's just a display to indicate the direction you should go to reach the waypoint you have selected. This is why it starts jumping around once you get close to the cache. As you approach the cache on foot the arrow will be pointing in the direction of the cache and the distance will be counting down. But once you walk past the cache location the pointer will spin around to indicate the waypoint is now behind you, right? Turn around and walk a few feet back the other way and now the cache is behind you again. Now you're doing the "drunken bee dance", walking around in circles at Ground Zero trying to get your GPS to read zero. Put the GPS away and start looking for the cache now, you're there!

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I do not believe that your Garmin 12XL has a "compass". What you perceive as a compass screen is a direction indicator screen. It will show you the direction you are headed, but it will not automatically show you which way is north.

As long as you are moving, whichever direction you are walking is the way the indicator will point. You must be moving in order for it to function.

I believe that it is more like 12 - 14 years old but then, I guess that does make it "at least" 4 years old.

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I do not believe that your Garmin 12XL has a "compass". What you perceive as a compass screen is a direction indicator screen. It will show you the direction you are headed, but it will not automatically show you which way is north.

As long as you are moving, whichever direction you are walking is the way the indicator will point. You must be moving in order for it to function.

I believe that it is more like 12 - 14 years old but then, I guess that does make it "at least" 4 years old.

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It depends on the GPS you have. Unless your GPS has an electrronic magnetic compass built into it does not know which way you are holding it. If it does have an electronic compass it still needs to be calibrated. I have three GPS'rs with Triaxial compass but I do not bother with using the compass so none of mine are calibrated. In the early years of geocaching there was no such thing as a magnetic compass in a GPS. Once a cacher would walk a few feet the GPS would compass screen would work. As far as the arrow jumping around a lot at ground zero, that is normal. Keep in mind that GPS'rs that we use are going to be accurate to about 9 feet on average. Once your are within 10 or 15 feet just start looking.

 

The Garmin 12 XL is older technology that dates back more than 4 years, I was selling those before I retired and I have been retired for a long time. I would put the accuracy on that unit at about 15-20 feet.

 

I found this Data re. the Garmin 12 XL regarding updates that have been made, the most current update Was in Dec. 2001. I retired about nine years ago. I was a GPS buyer for a small chain of stored in N.Ca. I think A stoped ordering the 12XL soon after around 1999. Garmin tends to keep products in their product line for a very long time

 

Revision 2/2/97 - (see mountain performance & antenna connector, ... )

Revision 2/7/97 - (Ext. Ant, Current Draw, Dead Reckoning, Data Smoothing, ... )

Revision 6/29/98-(New hardware platform, CityPoint database)

Revision 3/8/99 - (Incorporate G-12CX Color GPS feature differences)

Revision 3/28/99-(Review by Bob Kaemmerer)

Revision 12/23/01-(Ver. 4.57 adds area-calculation feature)

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Your GPS 12XL is a very sturdy unit. We (still) have our original GPS 12, but it is relegated to back-up only should our upgrade fail.

 

Obviously these units lack amenities of newer units, but they still get you where you need to go. Utilizing 4 batteries is sometimes a good thing -- such as when ours delivered us from being stuck late at night in the middle of nowhere during a howling storm -- yes there is an embarrassing story that goes along with that, but... another time.

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Your GPS 12XL is a very sturdy unit. We (still) have our original GPS 12, but it is relegated to back-up only should our upgrade fail.

 

Obviously these units lack amenities of newer units, but they still get you where you need to go. Utilizing 4 batteries is sometimes a good thing -- such as when ours delivered us from being stuck late at night in the middle of nowhere during a howling storm -- yes there is an embarrassing story that goes along with that, but... another time.

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Your GPS does not know which way is north, or which way it is facing when you're holding it. It only knows its location relative to the array of satellites overhead. So in order for it to determine a direction you need to be moving...it calculates the direction in which you are moving through multiple, constant updates of your current location. Fortunately you don't really need to be moving very fast or very far for it to get a fix on your direction...just take 3 or 4 steps at normal walking speed and it will figure it out.

I have an older unit and that's what I have to do. Spinning around doesn't seem to help, you have to walk in a direction and then it will figure itself out and you'll adjust your path as necessary. Silly, but it's done what I've wanted it to do so far :)

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GPSr without a built in compass? Why not just carry a small separate magnetic compass? Line it up with the GPSr compass display. No walking or other movement necessary. Problem solved.

Because the GPSr can't communicate with the external magnetic compass to determine it's orientation. If the GPSr isn't moving (close to a waypoint) it won't be able to point to the waypoint without having its bearing.

 

If the GPSr doesn't know where north is, it can't point southeast to the waypoint (cache, dinosaur footprint, whatever you need to get really close to find).

Edited by seldom_sn
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People seem to be having a hard time understanding the concept of an electronic compass. I think it stems from the use (or misuse) of the term "compass" to refer to the function of a visual arrow on the GPSr that points the way to the waypoint.

 

"Why do I care which way north is? I just need to follow the arrow to the cache, right?" is the way some folks seem to think about it. They don't seem to get that the GPS can't determine which direction the cache is until it first knows which way IT is facing. Which requires either an electronic compass, or motion.

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GPSr without a built in compass? Why not just carry a small separate magnetic compass? Line it up with the GPSr compass display. No walking or other movement necessary. Problem solved.

Because the GPSr can't communicate with the external magnetic compass to determine it's orientation. If the GPSr isn't moving (close to a waypoint) it won't be able to point to the waypoint without having its bearing.

 

If the GPSr doesn't know where north is, it can't point southeast to the waypoint (cache, dinosaur footprint, whatever you need to get really close to find).

Yes the GPSr doesn't know it orientation to magnetic north but it does know the direction the cache is from you. So if the cache is south then the pointer will point south. So you look at your compass to see where south is and start walking in that direction. Soon the pointer on the unit knows which way your heading and the pointer now points in front of you. So a magnetic compass can help prevent you from walking in a direction only to find out you have to turn around and walk in another direction.

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Yes the GPSr doesn't know it orientation to magnetic north but it does know the direction the cache is from you. So if the cache is south then the pointer will point south. So you look at your compass to see where south is and start walking in that direction.

Thanks mpilchfamily,

Well said. I thought this was obvious, which is why I didn't elaborate in my post.

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