Common GPS problem?

I have 2 'portable' units. One is the Nuvi for the car. It doesn't have that problem. I can be entirely stationary, sitting at a stop light, and it knows precisely where I'm at, and it's directions remain accurate.

I have another 'portable' which I use for hiking and kayaking. It does have that spinning problem. i.e. It's ability to display direction ('bearing' or 'heading') is dependent on movement, and it does not possess a true compass which always points north. But, the graphical map, of where I'm located, and where I'm headed, remains accurate. It's just the nominal compass functions that go kerflooey.

GC

neither have ever experienced that problem

Regards, Ted

I find with the c550 if you move a couple inches the heading is correct. Its very sensitive.

No problems with my Nuvi 660 regarding this. Especially when WAAS is enabled.

http://www.garmin.com/aboutGPS/waas.html

I thought I remembered seing this question before. This thread may help clarify.

http://www.poi-factory.com/node/1670

I could see how you might have the problem if you start the unit cold and there has been no movement. I have a TomTom which also has a g-meter in it to keep track of your direction should the signal be lost. I have only really seen this when passing though tunnels or under long bridges.

No Problem with the Garmin 7200. No matter how slow or if you are stopped for a lite it just picks up when you start moving again.

Thanks everyone for your responses! Sounds like it's not a problem with most modern models out there, which is good news.

I have not had that problem with the C550.

C310x and no problem at all as far as that goes...

I haven't seen this problem with my Garmin 2720 - or my magellan meridium, which I have hike with for several years.

I have the c330 and i notice the spinning cursor sometimes....but only when i am leaving a driveway or parking lot...something the unit doesn't recognize as a driving area...but it never lasts more than a second...worst case ya gotta make a u turn because of it.

My NUVI 360 has no spinning problems either, looks like by reading the post here there are a lot of units that have over come this problem.

For newer units, the problem only happens when satellite reception is extremely poor -- like on very cloudy days in a car with metalized tint that blocks reception. But like everyone said, you just have to move a little to get back on track.

My Nuvi 350 do not have any of the problems.

My "guess" explanation for the spinning problem is:

I noticed that just by standing still in one location, the GPS coordinate can change back and forth a bit (up to +/- 10ft due to the slight inaccuracy of the unit and other errors including satellite orbit error).

For example, when the unit sensed that u r 3 ft north of your location, the cursor would point north, indicating that you have just travel north 3 ft. Then the unit thought you are some distance to the west and cursor would point west, etc.

I have the StreetPilot C550 and have not had that problem.

If you have ever watched a real time Survey Grade GPS calculate your position. You'd see that every second it resolves your position using the data available at that second. On those units, It uses a Least Squares Adjustment routine to store and calculate your position much more accurately than a commercial grade portable, and can eventually get your position down to sub centimeter accuracy. On the average GPS the accuracy may state it's 10' but, that’s ten feet in front of you then behind you then off to one side or the other. The patterns look like a shotgun blast after a few moments. Your compass arrow is chasing those momentary points, thus you’re spinning compass. As soon as you move in a constant direction it will smooth out. This much more evident in the handheld units with the "off road" style of routing. Auto units will occasionally show your car pointing in the wrong direction but that's about it.