Gps Anomolies

[+tekwizrd]

I am new to GPS and GeoCaching. I attempted my first find yesterday, but couldn't find the cache becuase my GPS was jumping all over the place. Even after a I stood still, the cursor would continue to move around in all different directions making it IMPOSSIBLE to figure out where my waypoint really was.

 

I tried two seperate locations and it did this consistently. I have a LowRance iFinder M + M unit. Any ideas to correct this are greatly appreciated. Thanks!!

[ImpalaBob]

This is kind of normal behavior due to multi-path signaling from reflections and such. Sitting still often makes matters worse. Plus or Minus 30 feet is a good rule. Get to where you think you should be and put the GPS away and start looking. Doing the druken duck dance is only funny to those watching you! ImpalaBob

[+Criminal]

If you’re trying to locate the cache by using the map page (zoomed way in) you will see the cursor doing that. Use the page with the arrow instead.

[+whistler & co.]

Were you in a cemetery? It always does that in cemeteries!

[Deego]

Like ImpalaBob said that's what happens So don't expect to count down to zero feet on the GPS and look down and see your standing on the cache, where would the fun be

 

once your at zero look around for the place where it could be.

[+PastorDIC]

The worse thing to do when looking at the GPS to find a cache is to be standing still. The only thing that will get you is the arrow spinning around.

 

Ine thing you can do if you are stuck is to go to 3 points near the cache, see where the arrow points, and then go to where those arrows meet.

[+Adventure.AS]

The worse thing to do when looking at the GPS to find a cache is to be standing still. The only thing that will get you is the arrow spinning around.

 

One thing you can do if you are stuck is to go to 3 points near the cache, see where the arrow points, and then go to where those arrows meet.

 

I wouldn't agree that stopping is "the worst thing to do". At the point, when the GPSr tells me I am somewhere nearby the cache, I stop and take out my pocket compass. Take the "bearing to the waypoint" from the GPSr, put that on the bezel and get the compass pointer centered on the North arrow. Now just look in the direction the bearing line is pointing and look for the tell tale signs of a hidden cache.

Edited April 21, 2006 by Maxima

[+tekwizrd]

Wow! I am really impressed with the responses here. All of these are viable and I will give them a try. It at least helps me understand that this is normal behavior.

 

I wasn't in a cemetary, but that phenomena sounds eerie. I will be getting a compass, I like that idea to follow up, once i close in on a cache. Also, Criminal, you suggested not use the map page and that's what I did. I assume you are suggesting using the NAV STEER page instead? I assume this won't jump around like the map page?

 

Thanks again everyone, I can't wait to try these suggestions!

[+Team Cotati]

The worse thing to do when looking at the GPS to find a cache is to be standing still. The only thing that will get you is the arrow spinning around.

 

Ine thing you can do if you are stuck is to go to 3 points near the cache, see where the arrow points, and then go to where those arrows meet.

 

That sounds interesting. I have a Magellan unit and it can do lots of strange things but standing still and having the "arrow spinning around" is one that I haven't yet been able to accomplish. Any suggestions?

Edited April 21, 2006 by Team Cotati

[+CharlieP]

I wouldn't agree that stopping is "the worst thing to do". At the point, when the GPSr tells me I am somewhere nearby the cache, I stop and take out my pocket compass. Take the "bearing to the waypoint" from the GPSr, put that on the bezel and get the compass pointer centered on the North arrow. Now just look in the direction the bearing line is pointing and look for the tell tale signs of a hidden cache.

 

That's good advice. If you keep moving, and there are obstructions nearby, the GPS may keep swapping satellites and will have problems computing a position. If you are having this problem in an area with nearby obstructions (trees, hillsides, buildings) go to the screen that shows the "accuracy" , hold the GPS at least head high, wait a minute and see how good the reception is. If it is not good (20 feet or more), take a few steps (to a more open area if possible) and see if it gets better. When the accuracy is at a good value, take the bearing and use the compass to shoot the bearing and then pace off the range to the cache location.

 

If you are having these problems in a very open area, that may be due to the GPS having an out of date almanac. Take the unit to an open area and give it about 15 minutes to find some sats and download the almanac info.

 

Having said all that, there are some locations, e.g. near buildings or rocky hillsides, where signal reflections will cause the GPS to "bounce around". Nothing you can do about that, but try to guess which bounce is the right one, and hope the cache owner used that one too.

Edited April 21, 2006 by CharlieP

[+Renegade Knight]

...

That sounds interesting. I have a Magellan unit and it can do lots of strange things but standing still and having the "arrow spinning around" is one that I haven't yet been able to accomplish. Any suggestions?

 

Turn off the compass. All GPSs have the same issue unless they have software that turns the pointer off when it thinks you are standing still.

 

Back on topic.

 

Your GPS has an error to it. All do. If you are close enough to the cache to where you are standing inside the GPSs circle of error the GPS can't pinpoint your position relative to the cache and the pointer will point this way and that.

 

If you are walking to the cache the GPS keeps track of your movment by comparing your position to your last position. If the two are within that GPSs error (you slow down enough or stop) the GPS can't tell which way you are pointing and you will get the same result as before. Your position will jump about just from multipath and other natural errors and that's what will caus the pointer to go whacky. The exception is that if you have an Electronic compass the GPS will know which way you are facing and it can point the way.

 

In other words, take two steps and your GPS will point the way, or if you are within 20' of the cache it's time to start looking.

 

There are tricks to find ground zero (That involve the hula dance and drunken bee walk) but that's another topic.

[+Team Cotati]

...

That sounds interesting. I have a Magellan unit and it can do lots of strange things but standing still and having the "arrow spinning around" is one that I haven't yet been able to accomplish. Any suggestions?

 

Turn off the compass. All GPSs have the same issue unless they have software that turns the pointer off when it thinks you are standing still.

 

Back on topic.

 

Your GPS has an error to it. All do. If you are close enough to the cache to where you are standing inside the GPSs circle of error the GPS can't pinpoint your position relative to the cache and the pointer will point this way and that.

 

If you are walking to the cache the GPS keeps track of your movment by comparing your position to your last position. If the two are within that GPSs error (you slow down enough or stop) the GPS can't tell which way you are pointing and you will get the same result as before. Your position will jump about just from multipath and other natural errors and that's what will caus the pointer to go whacky. The exception is that if you have an Electronic compass the GPS will know which way you are facing and it can point the way.

 

In other words, take two steps and your GPS will point the way, or if you are within 20' of the cache it's time to start looking.

 

There are tricks to find ground zero (That involve the hula dance and drunken bee walk) but that's another topic.

 

How will turning off the compass make the pointer spin around?

[+Renegade Knight]

...How will turning off the compass make the pointer spin around?

 

Based on the smilies it doesn't sound like you are serious but I'll answer anyway, JIC.

 

Your GPS only knows one thing. Where you are. You can plug in where you would like to go. However for it to point the way it has to know which way you are facing. The only way it can do that is to compair the point it just calculated for where you are to the last point it had calculated. It assumes you are moving that direction and points the way. When you stand still your location is fixed but the normal position error will move you around your fixed point so the pointer goes wacko. (Probably worse on garmins than Magellans due to the magellans averging).

 

A compas changes that. By knowing the declination from a table it can sence which way you are pointing and so it can keep the pointer pointed the right way. Turn of the compass and you turn off the GPSs ability to know which direction you are facing when you are standing still.

 

There are probably variations on the actual math the GPS uses but that's the gist of it.

[+soonerdg]

...How will turning off the compass make the pointer spin around?

 

Based on the smilies it doesn't sound like you are serious but I'll answer anyway, JIC.

 

Your GPS only knows one thing. Where you are. You can plug in where you would like to go. However for it to point the way it has to know which way you are facing. The only way it can do that is to compair the point it just calculated for where you are to the last point it had calculated. It assumes you are moving that direction and points the way. When you stand still your location is fixed but the normal position error will move you around your fixed point so the pointer goes wacko. (Probably worse on garmins than Magellans due to the magellans averging).

 

A compas changes that. By knowing the declination from a table it can sence which way you are pointing and so it can keep the pointer pointed the right way. Turn of the compass and you turn off the GPSs ability to know which direction you are facing when you are standing still.

 

There are probably variations on the actual math the GPS uses but that's the gist of it.

 

A handfull of GPSrs have an electronic compass that works when standing still. Most however do not have a true compass, just a screen that looks like a compass but only works when your moving at least 3 mph. The best bet is to buy a magnetic compass to use in conjunction with the GPSr when you get close (within 100ft) to the cache. My GPSr has an electronic compass that works when standing still but even it jumps around when I'm really close to the cache. I still use a standard compass to help zero in on the location. It's also handy to have if your GPSr should ever fail and you have to find the car.

[+Adrenalynn]

I've found the best solution when I'm 30ft out is to put my GPS in my pocket and start looking for the cache... YMMV.

[+Team Cotati]

I've found the best solution when I'm 30ft out is to put my GPS in my pocket and start looking for the cache... YMMV.

 

Thanks, I tried that but my compass pointer still won't spin around. Strange.

[+Adrenalynn]

I've found the best solution when I'm 30ft out is to put my GPS in my pocket and start looking for the cache... YMMV.

 

Thanks, I tried that but my compass pointer still won't spin around. Strange.

 

Yes it does. Put it in your pocket and then twirl. voila! Pointer spins.

 

I'm curious though: What leads you to believe that absolutely everyone is responding to you rather than the OP? Maybe my browser is fibbing, but it doesn't appear that I quoted you in my earlier post... ???

Edited April 25, 2006 by Adrenalynn