60CS Satellite Acquisition and Lock

[+Oriented]

Hi. I bought 60cs last week to hopefully replace my etrex vista mainly for speed and the larger & color screen. I certainly expected it to be as accurate as the vista -- which I've been very happy with.

 

However, in a side by side (10ft apart and switching locations, multiple days) comparison, the vista *always* outperforms the 60cs by consistently claiming 12' or better accuracy vs. 20+' on the 60cs. And at a geocache, the vista is almost always "very close", whereas the 60cs tends to be significantly off, even after letting it lay flat on a log for 5min to "settle".

 

I have never seen the 60cs claim better than 20' accuracy. Both have WAAS enabled and the vista definitely is picking up a WAAS satellite (#35) reliably. (I'm in central North Carolina)

 

The only clue I have as to what might be going on is on Satellite screen. The 60cs seems to acquire and release satellites *continuously*, even while stationary. Ie, one second I'll have 5 or 6 satellites locked, the next second only 2 or 3 of those remain, a few seconds later will have the 5 or 6 again and so forth all the time.

 

Do other users see this?

 

Unit had 3.40 firmware when I bought it. Upgraded to 3.70 and did not help.

 

Suggestions appreciated. My only idea at this point is to exchange it for another 60cs unit.

 

--tony

[+graldrich]

I do not have that unit but have friends that have it.That is not normal,it should perform a little better than the Vista.

[peter]

whereas the 60cs tends to be significantly off, even after letting it lay flat on a log for 5min to "settle".

How are you orienting the two units? The Vista should be almost flat, but the 60cs should be nearly vertical for best performance.

 

You mentioned that WAAS was enabled for both units, but were both actually using WAAS corrections? That would be indicated by little "D's" appearing on some or all of the satellite signal strength bars on the Satellite Page. It takes awhile with good WAAS reception for a unit to initially get the WAAS almanac data, so the 60cs may not have the necessary data yet.

[+sTeamTraen]

However, in a side by side (10ft apart and switching locations, multiple days) comparison, the vista *always* outperforms the 60cs by consistently claiming 12' or better accuracy vs. 20+' on the 60cs.

Have you calibrated it against a known location such as a trig point ? Accuracy is only an estimation of how wrong the position is; maybe Garmin have changed their algorithm for determining that.

[+Rubberhead]

You might have a GPSmap 60C with a weak receiver. I know a couple of cachers (husband and wife) that ordered two GPSmap 60C's. The "His" GPS had a bum receiver and was significantly outpreformed by the "Her" GPS. He claimed so sort of underhanded dealing in the GPS allocation process but finally sent it back to Garmin and they fixed it. His is now very happy.

[BilgeRat]

You might also try going to firmware V 3.60. V 3.70 changes the way that the WAAS birds lock on, do a search on here, there were a few threads on this subject. My 60C routinely displays accuracy of +/- 6-8'; I'm happy with the way mine locks on the WAAS birds, so I have not "upgraded" to V 3.70.

Tom

[Delaypat]

I usually average around +/- 15-19 now I'm wondering if I should send my unit back??? I mean it gets me to the caches just fine.....hummm..what should I do???

[moonpup]

accuracy comes down to what the position of the satellites are on any given day in your location. some days I get 8-10 ft accuracy while other days I get 12-20 ft and on other days 22-35... this happens to be in my car on my commute to and from work..

 

just don't sweat it...

[+Oriented]

However, in a side by side (10ft apart and switching locations, multiple days) comparison, the vista *always* outperforms the 60cs by consistently claiming 12' or better accuracy vs. 20+' on the 60cs.

Have you calibrated it against a known location such as a trig point ? Accuracy is only an estimation of how wrong the position is; maybe Garmin have changed their algorithm for determining that.

 

Yes, this is what I thought at first: that Garmin improved their numerical analysis a bit and the 60c quoted errors were more accurate (so to speak:-). But after realizing it was generally quite a bit less accurate than the Vista on 3 actual caches, and that the satellites wink in and out continuously, I think something else is going on....

[+Oriented]

whereas the 60cs tends to be significantly off, even after letting it lay flat on a log for 5min to "settle".

How are you orienting the two units? The Vista should be almost flat, but the 60cs should be nearly vertical for best performance.

 

You mentioned that WAAS was enabled for both units, but were both actually using WAAS corrections? That would be indicated by little "D's" appearing on some or all of the satellite signal strength bars on the Satellite Page. It takes awhile with good WAAS reception for a unit to initially get the WAAS almanac data, so the 60cs may not have the necessary data yet.

Hmm, I did have the 60c flat. Is it really better to have it vertical? I'll try that tomorrow, but it does seem to be designed to use "flat" when in hand.

 

Regarding the WAAS almanac, might it take hours or days to gather this? (I understand the concept of WAAS corrections, just not sure 'almanac' refers to...)

 

thanks

[+Sputnik 57]

The 60 uses a quad helix antenna that works best when the unit is held vertically. It enables the antenna to "see" birds nearer to the horizon.

 

I'm not sure WAAS has a separate almanac. The almanac is the listing of where the satellites are at any given moment. 15 to 20 minutes of clear skies should allow the entire almanac to load. It doesnt need to be reloaded unless you do a hard reset, or move more than about 500 miles with the unit off.

[peter]

Hmm, I did have the 60c flat. Is it really better to have it vertical? I'll try that tomorrow, but it does seem to be designed to use "flat" when in hand.

 

Regarding the WAAS almanac, might it take hours or days to gather this? (I understand the concept of WAAS corrections, just not sure 'almanac' refers to...)

There's a good description of WAAS at:

http://www.gpsinformation.org/dale/dgps.htm

Check the section titled "Loading the Almanac" for suggestions on a step-by-step procedure for ensuring that your Garmin receiver is properly getting the almanac data needed for WAAS (i.e. the locations in space of the various WAAS satellites).

 

It shouldn't take longer than about half an hour, but you need a clear view of the horizons where the WAAS satellites are located (SE and/or SW depending on your location) during this time.

 

And yes, you should have the 60c/cs models reasonably close to vertical, especially if you're in an area with marginal reception.

[Delaypat]

Dont know how, but I just got a 11 D's.........WOW....That took it down to +/-7ft.......That was pretty cool...I hope it easy now to get them...This was in my car also.......I must have just been in a good spot.....Awesome though....

[+blindleader]

Hmm, I did have the 60c flat.  Is it really better to have it vertical?

Absolutely, though orientation is slightly less critical with the quad helix antenna. because it has better off-axis sensitivity than a patch.

 

Regarding the WAAS almanac, might it take hours or days to gather this? (I understand the concept of WAAS corrections, just not sure 'almanac' refers to...)

I don't know if this information is included in peter's link, but I believe the the cycle time for dowloading the ephemeris (same thing as almanac) is ten or twelve minutes, and similar for correction data from the WAAS satellite.

 

FYI the almanac (or ephemeris) is the database your GPS receiver needs to calculate exactly where each satellite is at a given instant. If you're using the GPS continuously, this data will normally be downloaded automatically as it is updated.

[Delaypat]

I have no problem getting waas now...And you are right, 10-12 mins was about the time it took becuase I was waiting for my GF to get out of school and held it on my dash for about that time.....Cool beans....

[+Oriented]

Regarding the WAAS almanac, might it take hours or days to gather this? (I understand the concept of WAAS corrections, just not sure 'almanac' refers to...)

There's a good description of WAAS at:

http://www.gpsinformation.org/dale/dgps.htm

Check the section titled "Loading the Almanac" for suggestions on a step-by-step procedure for ensuring that your Garmin receiver is properly getting the almanac data needed for WAAS (i.e. the locations in space of the various WAAS satellites).

 

It shouldn't take longer than about half an hour, but you need a clear view of the horizons where the WAAS satellites are located (SE and/or SW depending on your location) during this time.

This was EXACTLY the problem. It's working great now. Even tho I had used the GPS for a few hours it apparently never had a long / good view of a WAAS satellite.

 

Its very surprising Garmin doesn't provide a real explanation of WAAS and "loading the almanac" in the manual. I'm sure this issue generates a lot of support calls and returns; I certainly almost returned my unit.

 

thanks!