More accuracy problems

[+crazygramma]

My new Garmin Vista Cx seems to be not trustworthy. Most times that I find caches the gps tells me I am any where form 20 to 60 feet or more away when I'm standing right over it. Yet it says it's accuracy is within 7 to 14 feet! Yet once in a while it is dead on accurate. The problem occurs even on clear days in wide open fields. How can this be? It was always somewhat off sometimes, but it's more and more often now. I'm having more frustrations than fun now. Is it time to do a total reset?

[mtbikernate]

The accuracy circle is always going to be a bit on the optimistic side. The nav screen telling you it's 20-60ft away is probably the more accurate one. If you get much closer than that, really, it's time to use your eyes, not the GPS.

[+StarBrand]

Sounds like it is working fine to me. As a general rule - you will have accuracy anywhere from 10 to 40 feet. Remember the hider's GPSr was getting accuracy at about the same rate. His 20 foot accuracy plus your 20 foot could be as much as 40 feet away. So you can expect to find the cache within 20 to 80 feet of where you say ground zero is at. Very typical. I mostly find them at under 30 feet but occasionally more. Put the GPSr away when it says 20 foot or so and start looking.

 

Also the stated accuracy is just an estimate based on satellite configuration. I am told it is an estimate with something like about 80-90% confidence. So even that number is not accurate.

Edited January 28, 2007 by StarBrand

[+mamid]

Is WAAS any good if you are in Canada? I'm about an hour north of the border by car (driving, not degrees) and am wondering if turning WAAS on would help?

[+StarBrand]

Is WAAS any good if you are in Canada? I'm about an hour north of the border by car (driving, not degrees) and am wondering if turning WAAS on would help?

Should work and will help your accuracy some but you just don't know if the hider was using it or not. So you may still have the same problem.

[+mamid]

I was told by another local cacher to "turn it off cause it wastes batteries." I don't give a hoof about batteries. I want accuracy.

[+StarBrand]

I was told by another local cacher to "turn it off cause it wastes batteries." I don't give a hoof about batteries. I want accuracy.

My own experience is that it maybe shaves 5 to 10% off the life of batteries - I just leave it on all the time.

[+TexasGringo]

Try updating your unit with new software. The latest update for your unit is 11/12/2006. Download the "WebUpdater" and connect the USB cable to your pc then GPS and get the updates.

 

http://www.garmin.com/products/webupdater/howtoinstall.jsp

Edited January 28, 2007 by GURU4HIRE

[+Prime Suspect]

Is WAAS any good if you are in Canada? I'm about an hour north of the border by car (driving, not degrees) and am wondering if turning WAAS on would help?

It won't help if there are no reporting groundstations for your area.

[+tomfuller & Quill]

Is WAAS any good if you are in Canada? I'm about an hour north of the border by car (driving, not degrees) and am wondering if turning WAAS on would help?

It won't help if there are no reporting groundstations for your area.

The two WAAS sats are in geosynronus orbit (over the equator) . They serve pretty much all of the Western hemisphere from 60 degrees North to 60 degrees South. The only groundstations I am aware of are for the old LORAN system which I used before GPS sats were launched.

If you use good batteries 1.40 + volts (not the 1.2 volt rechargeables) WAAS will help accuracy if you get a lock on a WAAS sat.

[+mamid]

which ones are the waas sats? or are they just random?

[+ICHTHYS]

The WAAS sats are the highest #'s, I believe they start in the 30's. WAAS is hard to get in tree cover though.

 

Some people shut WAAS off because they stand no chance of picking them up when in the woods so why waste battery life looking for them.

[+Prime Suspect]

Is WAAS any good if you are in Canada? I'm about an hour north of the border by car (driving, not degrees) and am wondering if turning WAAS on would help?

It won't help if there are no reporting groundstations for your area.

The two WAAS sats are in geosynronus orbit (over the equator) . They serve pretty much all of the Western hemisphere from 60 degrees North to 60 degrees South. The only groundstations I am aware of are for the old LORAN system which I used before GPS sats were launched.

If you use good batteries 1.40 + volts (not the 1.2 volt rechargeables) WAAS will help accuracy if you get a lock on a WAAS sat.

You don't seem to have a grasp of how WAAS works. I would suggest taking a look at the Wikipedia entry. To summarize, if there's no WAAS ground station for your area, most of the WAAS data you will get will not be of use to your GPS. Currently, there are 29 ground stations covering the US and Puerto Rico.

 

Also, whether or not 1.2v batteries will work is model-dependent. Most of the newer Garmins have NiMH battery (1.2v) settings, so obviously they don't consider it an issue.

[+Arndtwe]

if it annoys you you can buy an external antenna, something that is very useful

[+FLYRFN]

Getting back to the real problem, Vista's have electronic compass's that need to be recalabrated when ever the batteries are replaced. If you recalabrate the compass it should work much better.

[+tomfuller & Quill]

Back in the days of Selective Availability I used a CMT-MCGPS to locate PA State Forest corners. I would sit on a corner for 3 three minute sessions. I brought the unit back to the office, downloaded to the server, then called up the CORS data for the hours that I was collecting. This is how Differential GPS works. The PA Bureau of Forestry also operates 3 base stations for the use of state employees.

The US Coast Guard and the Canadian Coast Guard also run Real Time Corrections ground stations

To use RTCM-104 you have to use a separate receiver plugged into your compatable GPS unit.

 

For everything you ever wanted to know about GPS accuracy visit http://edu-observatory.org/gps/dgps.html

 

Check out the link by Dennis Milbert

 

Most of the information that I find on Wiki is highly suspect. "An expert is a person form out-of town that thinks he knows what he is doing"

 

Tom Fuller

Crescent, Oregon

[+trainlove]

On my Magellan Gold, the WAAS satellites do not have numbers, just W and W, not to be confused with the W of the compass rose (along with N, E and S).

Not having numbers I can't tell the signal strengths but only if they are being received or 'nearly' being received.

 

I had thought that the WAAS signal was somehow different from the GPS signals, but it appears to be the same. I.E. The WAAS satellites really should have a number displayed on my GPS, each GPS satellite has 2 numbers, a body number which means nothing and a PRN (Pseudo Random Key Number) which is what Garmin's and Magellans display (at least the few models I've used and perhaps ALL).

[+crazygramma]

Try updating your unit with new software. The latest update for your unit is 11/12/2006. Download the "WebUpdater" and connect the USB cable to your pc then GPS and get the updates.

 

http://www.garmin.com/products/webupdater/howtoinstall.jsp

 

This is a very late reply to your post of 1/27/07. The combination of me being somewhat of a technophobe and having a Mac, which can't be used with Garmin, prevented me from updating my software for awhile. Last month I found a geocacher friend with a pc who updated my unit. It has worked fine since then. I am happily geocaching once again. Thank you for an easy solution to my problem.

[+maby]

 

This is a very late reply to your post of 1/27/07. The combination of me being somewhat of a technophobe and having a Mac, which can't be used with Garmin, prevented me from updating my software for awhile. Last month I found a geocacher friend with a pc who updated my unit. It has worked fine since then. I am happily geocaching once again. Thank you for an easy solution to my problem.

 

If it was a recent purchase, it must have been sitting on the shelf for a while - there was a serious problem with the Cxs released last summer - if you do a search you will find many owners complaining of errors of sixty feet or more. Garmin released new firmware and, although they never admited to fixing the positioning algorithms, the complaints stopped...

 

Martin