Haven't used my 176c for a while, so I started using it this week to get ready for my trip next week. I performed the Nov update from Garmin's site, and am using Mapsource software. The accuracy of the tracking is unbelieveably off. Even my tracks from going home last night and the tracking from coming into work this morning are off in some places. At first I thought it might be the new external antenna I'm using, but the speedometer on the gps is accurate. Can anyone tell me what I can do?

* Map Datum is set at WGS 84
* Heading is set at Auto Mag Variance
* WAAS is off
* Accuracy has been from 60 to 180 ft
* DOP is at 4.1 or so
* Differential is NONE

I really think the problem is with the map that is in the gps. It shows sharp bends in the interstate where there may be no bend at all, or a very gradual curve. I remember the unit being much more accurate this summer when I bought it.

It'll be a very frustrating trip if I can't get this accuracy in line.

Have you tried it without the external antanna yet? If your accuracy is only 60 to 180 feet then you must only be getting reception from 3 or 4 satellites to get that bad of accuracy. On mine if I'm getting a weak signal on only a few then I'll have accuracy like that. Otherwise when I'm getting a good signal I'll be running from 16 to 30 feet accuracy.

Jim there is always some margin of error with tracks and position vs. where you really are. Do you have an option thats sets the unti to "Snap to Road"?

How far is your track off? Way more than the 180 ft. variance?

Levi, I popped the external antenna off and put the original on, and it didn't seem to make a difference. Usually I'm picking up about 6 or 7 satellites with the ext.

Art, I know what you mean about the standard variance. But usually my tracks would be on or just a little off of the actually highways. Last night and today I'm talking up to an inch away on the screen (forgot to look at the ft variance at that point), and was almost never on the highway. Plus, the layout of the roads on the map are way off sometimes. Maybe I'll create a new set of maps in Mapsource, d/l it and see what happens. I have a very large database of maps loaded now, all the counties from St Louis to the UP, and all of the UP. From my calculations, I have plenty of memory left. But I wonder if having a much larger set of maps could cause this problem. Maybe it was just the satellites at that time, and it might be better on the way home tonight.

There's an inch between routes? zoom out!!! It'll get smaller! :D

I doubt changing the maps in the GPS will make a difference. I can't remember if the GPS itself has a setting for the number of points (detail) in a track, but when I go into MapSource I reduce the detail of the track just for memory sake and it gets much less accurate.

Use the measuring tool in MapSource to see how far off (in feet) the tracks really are from the road. Mine are sometimes 50ft. off to one side. Also, I have noticed in at least one area by my father-in-law's cabin in Atlanta that when riding a particular county road my track ALWAYS goes haywire and there are no trees obstructing that particular area, must be some sort of government mind control test beacon in that area . . . ;-)

Allright, I paid a little more attention on the way home last night. The "accuracy" box only varied from 6 to 16 ft variance, not too bad. But with that little of a variance, my tracking was up to 900 ft (according to the little legend on the screen, 1 inch = 300 ft) off of the actual hwy. Then I realized that in the areas that are really off, I haven't downloaded the detail maps from MapSource, so maybe that's the problem. I guess the hwys become more accurate when d/l from the software, I'll have to try it and see.

Originally posted by JIM FRITCH@Jan 9 2004, 10:46 AM
Then I realized that in the areas that are really off, I haven't downloaded the detail maps from MapSource, so maybe that's the problem. I guess the hwys become more accurate when d/l from the software, I'll have to try it and see.
No idea, I would think that major highways are the same in the basemap as on the CDs.

Maybe you're experiencing the same thing I do by my dad's cabin. See if the track jumps off in the same place, could be some strange interference with the sattelite signal.

Fritch,
I would lean toward the basemap being off.
The dl info does seem to be more accurate on my MAP76.
One time I even had the basemap completely delete an Interstate Highway I was traveling on for about 30 miles. My wife thought it was hilarious that I was freaking out because it showed me on no road at all!
"How much did that thing cost you?" she asked as she handed me the Rand Mcnally!

Originally posted by BCthetwo@Jan 9 2004, 01:30 PM
My wife thought it was hilarious that I was freaking out because it showed me on no road at all!
"How much did that thing cost you?" she asked as she handed me the Rand Mcnally!
LOL...my wife does the same thing. There's a 15 mile stretch of state hwy about 12 miles from my house that doesn't show up at all either, and my wife gives me the same static. There's also a county road, about 2 yrs old, accross from my subdivision that doesn't show up either. I thought the November Garmin update would take care of some of this, but it hasn't. Too bad Garmin can't be more accurate with this kind of info. I've been spoiled at work...I've been driving new Infiniti's with the built in navigation systems for demos, and they are cool as heck.

If anyone knows of a way to correct the basemap, please let us know. I emailed Garmin yesterday, but haven't heard from them yet.

Is that the same nav system that's in the Nissans?
My mom has a Nissan Murano with a nav system in it. Even has audio with a woman's voice that tells you when to start looking for upcoming turns! Seems like it's very capable and accuracy is excellent. Every time she comes to visit I've got to take that thing for a spin just to play with that system. I've got to figure out a way to get audio added to my hanheld while sledding. A girls voice comes on in you're helmet that tells you about upcoming stuff! LOL

Yes, same system. I've used it in the FX45's and the Q45's, awesome system. That program has so many features, it's unbelieveable.

Originally posted by JIM FRITCH@Jan 9 2004, 10:46 AM
Allright, I paid a little more attention on the way home last night. The "accuracy" box only varied from 6 to 16 ft variance, not too bad. But with that little of a variance, my tracking was up to 900 ft (according to the little legend on the screen, 1 inch = 300 ft) off of the actual hwy. Then I realized that in the areas that are really off, I haven't downloaded the detail maps from MapSource, so maybe that's the problem. I guess the hwys become more accurate when d/l from the software, I'll have to try it and see.
I rode to the tip of whitefish point in the U.P. When I have the map detail turned off it looks as if I drove into lake superior by a small amount, but when I turn the gps map detail back on my track shows me at the very tip of the point, so I believe some changes do happen when toggling between gps map detail on and off.

I loaded the base map for boating and find it is not nearly as accurate as my original software.
When my boat is at my dock (with the original software) it was very accuate in reference to the street. After I loaded the Recreation software which was supposed to show channels and bouy markers my boat is parked half way down the road.
I contacted Garmin and they tell me to load a blank map to reset my handheld to the original settings. In my experience Garmins tech support is excelent but that response was pretty lame. When I figure out what they are talking about Im going to reset and Ill post my findings.
I have the GPS III+.