Two Questions On Garmin 60x

[GeoBobC]

Question 1: why doesn't Garmin allow the use of more than two WAAS satellites for positioning? If, for example, there are 6 non-WAAS satellites in view, and 3 WAAS satellites in view, the 60x will use at most 2 of the WAAS satellites. Wouldn't the use of the 3rd WAAS satellite improve accuracy?

 

Question 2: I have noticed on numerous occasions that I end up with more than one active log on my 60x from a one or two hour trek, even when excellent satellite coverage exists for the entire duration. Has anyone else experienced this? Any ideas as to why? It's not real painful, as the units can be merged in Mapsource, but it's still odd. I could understand it if the 60x temporarily lost satellite contact, but I'm seeing six to eight birds consistently, with EPE in the teens.

[Neo_Geo]

I can't answer number one, but the unit will create a new active log when re-acquiring lost reception and when the unit is powered-on and acquired reception - or if GPS mode or the tracking feature is turned off and then back on.

 

Other than that, it should produce one continuous track log. Did you just update the firmware to 3.00? Perhaps a new bug?

[+EraSeek]

Question 1: why doesn't Garmin allow the use of more than two WAAS satellites for positioning? If, for example, there are 6 non-WAAS satellites in view, and 3 WAAS satellites in view, the 60x will use at most 2 of the WAAS satellites. Wouldn't the use of the 3rd WAAS satellite improve accuracy?

 

 

Well, I can answer this one. There are 2 things WAAS sats can do. One is to act somewhat like other sats in providing a position solution. How ever, the WAAS sats are not the best for this. The regular GPS sats do a better job in this rangeing capability.

 

The second thing WAAS sats do, and this is really what they are there for, is to provide corrections for the GPS satellites. As the GPS sats send their data to your GPS their signal is slowed by an active ionosphere. Timing is everything. One nanosecond of error throws your position off by a foot or so. WAAS corrects this and other errors (clock, postion of the sats..). WAAS is good. However there are times when corrections are less necessary than others. At night the ionosphere is pretty calm.

 

Older Garmin GPS's will save 2 slots for WAAS sats. I believe the newer ones only use one WAAS sat at a time. There are 4 US waas sats up. All of these waas sats send the SAME data for a zone, so only one WAAS sat is needed. WAAS sats do not all send the very same data, because each WAAS sat covers only so many zones. However, they have big crossover, and whatever zone you are in you will recieve the needed data. The same ionospheric corrections for the US are covered by all 4 WAAS sats. Your GPS figures out where you are and uses the ionospheric corrections for your position. Thus, they are not the best for locating where you are, and each of them provide the same corrections, so you only need one at a time. And really that is best.

Edited July 28, 2006 by EraSeek

[Hertzog]

Well, I can answer this one. There are 2 things WAAS sats can do. One is to act somewhat like other sats in providing a position solution. How ever, the WAAS sats are not the best for this. The regular GPS sats do a better job in this rangeing capability.

The SiRF models don't use the WAAS satellites as part of the postion solution, just for the correctional data.

[+Munin]

Did you just update the firmware to 3.00? Perhaps a new bug?

Since I'm running with the 3.00/2.70 firmware combo, I left my 76CSx on overnight to do a simple test - logging a track at 30 second intervals for about 8 hours. Ended up with a single, continous active track log.

 

GeoBobC - what options are you using for your track logs? (Distance/time/auto, interval setting.) I could try setting my GPSr up the same way and log some tracks while I'm running around this weekend, see if anything wonky happens.

[+paulamur]

I can't answer number one, but the unit will create a new active log when re-acquiring lost reception and when the unit is powered-on and acquired reception - or if GPS mode or the tracking feature is turned off and then back on.

 

Losing reception is something that doesn't happen very often I have only lost reception going through tunnels, and inside the Astoria Column (Astoria, Oregon), but I did maintain a lock when descending the first 100' or so.

[8mmag]

I can't answer number one, but the unit will create a new active log when re-acquiring lost reception and when the unit is powered-on and acquired reception - or if GPS mode or the tracking feature is turned off and then back on.

 

Losing reception is something that doesn't happen very often I have only lost reception going through tunnels, and inside the Astoria Column (Astoria, Oregon), but I did maintain a lock when descending the first 100' or so.

 

What is the Astoria Column ????

[GeoBobC]

As for getting two ore more track logs: I have the unit set as "Auto - More Often". Let me emphasize that I have no indication of a lost signal - I'm seeing six to eight satellites or more consistently. This phenomena occurs about 10% of the time for me. I wonder if it has something to do with WAAS, as in the unit says "OK - WAAS isn't working well so turn it off", and in that split second it starts a new track log.

[Neo_Geo]

As for getting two ore more track logs: I have the unit set as "Auto - More Often". Let me emphasize that I have no indication of a lost signal - I'm seeing six to eight satellites or more consistently. This phenomena occurs about 10% of the time for me. I wonder if it has something to do with WAAS, as in the unit says "OK - WAAS isn't working well so turn it off", and in that split second it starts a new track log.

Which firmware and GPS software are you running?

[+paulamur]

I can't answer number one, but the unit will create a new active log when re-acquiring lost reception and when the unit is powered-on and acquired reception - or if GPS mode or the tracking feature is turned off and then back on.

 

Losing reception is something that doesn't happen very often I have only lost reception going through tunnels, and inside the Astoria Column (Astoria, Oregon), but I did maintain a lock when descending the first 100' or so.

 

What is the Astoria Column ????

 

Click here for more info on the Astoria Column

[+Munin]

I wonder if it has something to do with WAAS, as in the unit says "OK - WAAS isn't working well so turn it off", and in that split second it starts a new track log.

Taking advantage of the marvels of indoor reception, I fired up my 76CSx and let it sniff around until it had a reasonable lock (20-30' EPE), but no WAAS. Started a track log at 30s intervals (thanks to this silly thing called "work" I can't go running around to try other logging options just yet ), let the log run for a while. Moved the GPSr up against the window, where it was able to pick up WAAS corrections, and let the logging continue for a while. Finally moved the GPSr back to where it started, watched it lose WAAS, and again let the logging run. Still ended up with a single, uninterrupted active log. I think we can rule out WAAS - gaining/losing coverage doesn't seem to trigger a break in the active log.

[GeoBobC]

I'm running the latest: 2.70 SirF/3.00. I've experienced this in previous versions as well.

[Grasscatcher]

I would almost bet what is causing the additional active track log(s) to be created is loose batterie(s). Connection lost only for an instant and active log restarted but lost connection not long enough to have to restart unit.

 

Was there any "Jarring" on your trek? I've had it happen several times on an ATV trip on rough terrain. Small piece of open cell foam in batt compartment fixed it.

[GeoBobC]

Batteries: very good theory! Temporary loss of power, even for a moment, could cause a restart/new track. Perhaps the loss is too brief to even notice. I'm using Duracell mnh 2600 AAs.

[Grasscatcher]

I bought an 8-Pack of Rayovac Nimh that were the world's worst... turns out they are about .010 shorter than others I use. The piece of foam cured the prob.

[+EraSeek]

Well, I can answer this one. There are 2 things WAAS sats can do. One is to act somewhat like other sats in providing a position solution. How ever, the WAAS sats are not the best for this. The regular GPS sats do a better job in this rangeing capability.

The SiRF models don't use the WAAS satellites as part of the postion solution, just for the correctional data.

 

Thanks Hertzog, I didn't realize that. These SiRF models certainly do things differently! So would you say not using the WAAS sat for ranging is a benefit or not?

[8mmag]

 

Click here for more info on the Astoria Column

 

Cool! I lived in Battle Ground WA for 8 years, visited Astoria/Long Beach lots of times salmon fishing and never knew this existed. Thanks for the info.

[Neo_Geo]

I would almost bet what is causing the additional active track log(s) to be created is loose batterie(s). Connection lost only for an instant and active log restarted but lost connection not long enough to have to restart unit.

 

Was there any "Jarring" on your trek? I've had it happen several times on an ATV trip on rough terrain. Small piece of open cell foam in batt compartment fixed it.

Garmins have a known problem with rechargeable batteries losing contact. The result has always been a spontaneous complete shutdown of the unit requiring the user to manually turn the unit back on again. I'm not sayin' that this ain't the problem, but it would be the first time I ever heard of it.

 

If it were ME, I'd have an RMA number from Garmin about now, and boxed up and ready to ship tomorrow.

[Hertzog]

Well, I can answer this one. There are 2 things WAAS sats can do. One is to act somewhat like other sats in providing a position solution. How ever, the WAAS sats are not the best for this. The regular GPS sats do a better job in this rangeing capability.

The SiRF models don't use the WAAS satellites as part of the postion solution, just for the correctional data.

 

Thanks Hertzog, I didn't realize that. These SiRF models certainly do things differently! So would you say not using the WAAS sat for ranging is a benefit or not?

Personally, I don't thinks it's a big deal either way. As you mentioned in your previous post, the WAAS satellites aren't as good as the regular satellites for ranging, for a variety of reasons, but the earlier Garmin chips do successfully use them. I do wish they would display them on the satellite page when not being used though, so we would have a better idea of how visibile they are at a given location (the earlier Garmins do that).