67.3 Knots, GPS playing up..

[fishing111]

I have a Garmin GPS 72 ( not even a year old ), and yesterday I cleared the whole of the trip computer functions before I left as I have done on previous occasions, as I have just started a log to keep track of my fuel consumption. First thing of note was that when I had a look earlier in the day at the trip computer to establish how far I had travelled, it said that my max speed was 67.3 knots, which was odd because our boat doesn't do anywhere near that speed, then I thought that I must have left it on in the car, although that doesn't add up either as there is no chance of me towing the boat at 124.6 kmh, 90 to 100 kmh tops, so I cancelled of the max speed section and then when I checked it just now, this morning 6/03/08, it's saying that max speed is once again 67.3 knots! Does anyone have any ideas as to why this is happening, twice in the same day?
Some other dramas yesterday, related or not, could only get a 2D fix so I turned the unit on and off and then it went back to a 3D fix. Also at one stage in the day there was a vertical line on the screen and that's was it, no button's would work, so once again I turned the unit off and on, still wouldn't fix it, so pulled the batteries out and replaced them and then it worked again. I should also add that they were fresh energisers so I don't know how much trust I place in the odometer reading now. The Garmin unit ruffled me up a bit yesterday, I would have hated to have of relied on it in more challenging circumstances. Ideas welcome

[SatNav]

"GPS Playing up.."

1. Are you referring to "your" GPS or GPS in itself?

2. More inclined to suspect it is your GPS especially since you have recorded exactly the same max speed twice (in a row)

3. The other indications tend to also point to your GPS

[BaitThrower]

I have purchased "new batteries" from the store on occassion (good brand name ones) and found them to be less than "new" charge wise

I have also bought energiser NiMH 9v rechargeables that have only lived about 4 charge cycles before dieing and not holding a charge ever again. There are some defective ones that get through. Worth checking for actual charge for next outing, although usually the GPS accurately detects battery charge on its own battery charge indicator (if your unit has one?)

[John Martin]

I reckon your missus is taking the boat for a spin when you're at work

[fishing111]

Thanks guy's,

Satnav yeah my GPS, not sure if it was exactly 67.3 both times, but it was definately 60 something knots the first time, so both times in the 60's.

I take your point Baitthrower about the batteries, but I'm a paranoid prick about taking fresh batteries, I also take a 12 volt lead for emergency's.

John Martin not likely, I keep the key's on my person

[BaitThrower]

Could it be that perhaps for a split second or three that the GPS lost its tracking, and when it regained it, it calculated the speed based on its new location which may have been before it narrowed it back down to its accurate value, and hence calculated speed based on a position perhaps further away initially before it zeroed in, and hence, calculated a higher top speed for that moment? If that makes sense... If it was not exact both times, or you were not sure, then there might be a chance that was the cause twice in one day?

But that wouldn't explain the bit about the buttons not working, but may be plausible for the speed? Not sure. Just a thought

[Marlin_Mike]

I use energizer lithium batteries for longer life and never had a prob with my garmin 72

Mike

[goldcoastau]

Do you tow your boat.

[coucho]

do you live within the bermuda triangle? maybe there is a time space continum in your local area and as you travel through time stands still and you reach wrap 6 without knowing.
Serious though change the batteries buy some freshies if it plays up again time to test out your warantee

[thebun_88]

Could it be that perhaps for a split second or three that the GPS lost its tracking, and when it regained it, it calculated the speed based on its new location which may have been before it narrowed it back down to its accurate value, and hence calculated speed based on a position perhaps further away initially before it zeroed in, and hence, calculated a higher top speed for that moment? If that makes sense... If it was not exact both times, or you were not sure, then there might be a chance that was the cause twice in one day?

But that wouldn't explain the bit about the buttons not working, but may be plausible for the speed? Not sure. Just a thought

You are spot on. While attaining a fix (may have dropped out in your travels) there is error and a point has been logged, next point is more/less accurate over the time period you've traveled thus a higher (lower, but you wouldn't notice) maximum speed.