Hertzog

I've seen all you describe above - I went for an interesting drive in rural Mississippi a year ago; I knew how to get to where I was going efficiently, but it was a nice day and I had plenty of time, so I just followed the GPSr. I believe these problems are caused by the routing algorithms in the GPSr - in my case a 60CSx - rather than the data in the map product; I have never been able to duplicate my results in MapSource, which presumably has more robust and lest buggy routing algorithms.

Typically when people get those kinds of numbers under good conditions they have put the unit in the "Battery Saver" mode, so the first thing to check should be the top window on the System Setup page - this should read "Normal"; if it reads "Battery Saver", then this is your problem.

You could be right; I started looking at this originally on the B&W Vista and continued on the 60CS and 60CSx, but haven't any experience with later models. It's always possible that they have also changed it recently in the 60CSx firmware; when I have a chance I'll look at your post in more detail and compare that with the 60CSx.

When you are in the autocalibration mode the GPSr increments the measured elevation toward the GPS elevation by a small amount each second. The effect is that the elevation output will approach the GPS elevation exponentially with a time constant of about 30 minutes. You can see this by calibrating the altitude by a large offset, say 1000 feet, to create a "step function" and watching the elevation return exponentially to the correct value. There is also a faster "catchup" mode in which the time constant is reduced to about 30 seconds or so. The unit will enter this mode when it feels it has lost track for a while and regained it (I don't recall the exact conditions in which it does this). Sorry for the multiple post (see explanation on my previous post).

When you are in the autocalibration mode the GPSr increments the measured elevation toward the GPS elevation by a small amount each second. The effect is that the elevation output will approach the GPS elevation exponentially with a time constant of about 30 minutes. You can see this by calibrating the altitude by a large offset, say 1000 feet, to create a "step function" and watching the elevation return exponentially to the correct value. There is also a faster "catchup" mode in which the time constant is reduced to about 30 seconds or so. The unit will enter this mode when it feels it has lost track for a while and regained it (I don't recall the exact conditions in which it does this). Hope this edit isn't too confusing; I tried to edit my original message but accidently replied to it, then hopefully backed out of the reply and did an edit. If you see only one message from me, then it worked

The problem that started this thread was corrected by a software update some time back. This was of course a problem specific to the 60Cx/CSx models (probably the 76 "x" models as well).

Seems like an odd response, seeing as how Magellan has had 3-axis compasses for several years - apparently successful, although I don't have any direct experience with them. Just offhand, I can't think of why adding a third axis would dramatically increase calibration needs and temperature/pressure sensitivities over the 2-axis versions. I don't particularly want one that would work in any position - upside down for instance, or even vertically, although I know some would like that; I just want one that would make it less sensitive to being held perfectly level.

I don't think this is a problem with most 60CSx's just some; unfortunately mine is one of them I see in their latest manual (Rev E) however that they do acknowledge the problem; up through Rev D they were still reccomending the use of lithiums in cold weather.

The acquisition time from a cold start can be variable, depending on how long it has been off and how far you have moved from the previous location, but it rarely takes mine several minutes if I have good reception. The one exception to this is if you are moving when it is trying to acquire; it doesn't like that.

When you say you transferred the maps to the card, were you downloading them using MapSource or just copying them to the card?

Yep. The missed second was trying to read small type on on a web page; in looking closely at the units for "inductance" I shifted up one line in a table to "impedance". The missing 1000 is just plain embarrassing!

So, if my calculations are correct, 1 MAH = 1000 joules/coulomb; not sure what that would represent physically On a more practical note, over the last 50 years or so I have been very careful to "properly" capitalize the first letters when spelling out units named after people (i.e., I would have previously written "Joules/Coulomb"); Looks like I've been wrong all this time But then, none of my engineering friends ever called me on this Looking further, 1000 joules/coulomb is just 1000 V (guess I should have remembered that from my school days, but that was a long time ago - we still still considered 1 Hz to be 1 cps then)

This would definitely be a good data point. All of the tests I've seen (or done) are with the GPSr motionless, and I've often wondered if rotating it would cause transient current surges in the compass circuitry.

My results were a little lower using the 60CSx: I got 14.3 hours in the refrigeration with a pair of eneloops, vs. a previous 17.1 hours at ambient temperature. The battery capacities as measured by the C-9000 were 2% lower for the refrigerator test, so I factored that in to come up with an overall 85% number. It's possible that the external antenna increases the battery drain slightly; I've heard this in the past, but never measured it (the refrigerator test used the external antenna, but the ambient test didn't). When I get a chance I will run an additional ambient test with the external antenna to check this out.

I just reviewed some measurements I made about 2 years ago using 2500 mAh Duracells. At that time I got 12 hours on my B&W Vista, 29 hours on the 60CS, and 20.5 hours on the 60CSx; this would compare to your 14 hours on the 76S with 2500 mAh Energizers.

Interesting test; I'll do a similar one using an external antenna on my 60CSx; I'm running a a pair of eneloops through the C9000 in the R&A mode right now, to make sure they are topped off. When I ran a test with freshly charged eneloops earlier, I got 17.2 hours.

Theoretically it could, but the algorithms can't handle the pressure/altitude discrepancy (this was the first thing I tried years ago on my old B&W Vista; tried calibrating it to the GPS altitude, but it wouldn't accept it).

As the previous reply said, you can't. However, I'm guessing you want to see the GPS elevation because the barometric elevation will be wildly inaccurate inside the pressurized cabin. From the satellite page, press the menu key (lowest button on left), then pick the GPS elevation menu item. Or From the altitude page, press the menu key and choose calibrate altimeter. When it asks if you know the correct elevation, say no. When it asks if you know the correct pressure, say no. If it has a lock that allows it to know the GPS elevation, it will then ask if you want to use the GPS elevation and display it at the bottom of the page. (The first method is easier!) - Ed You can also try putting it in the fixed elevation mode. On the 60CSx this will cause the GPSr to log the GPS rather than the barometric elevation in the track log; the data fields will still display the barometric elevation, but at least you will have a record of the GPS elevation. I don't know if the HCx does this or not; the 60CS did not.

That was my point yogazoo had already told us what his settings were; I was curious about Marky's settings, since he reported no problems. Seems to me that the Colorado's NiMH setting has a bug (hopefully firmware) with respect to the shutdown voltage. In the past, the main difference I saw between the Alkaline and NiMH settings (Vista, 60CS, 60CSx) was the number of bars you got with fresh batteries; with the Alkaline setting fresh NiMHs would show only 3 out of 4 bars. What I just noticed is that with the eneloops I get 4 bars in the Alkaline setting (60CSx), so it may be that the new hybrids have a slightly higher "fresh" voltage than the earlier NiMHs, and the Alkaline setting may actually be more appropriiate for them.

Any chance your battery type was set to Alkaline instead of NiMH?

In a previous thread along these lines, someone said that rapid deceleration of a car could cause similar spikes, due to the "piling up" of the air in the front of the passenger compartment; that's something I've been meaning to check out, but haven't done so yet. My own observation (also not thouroughly checked out yet) is that when I drive my car over a pass the GPSr seems to underestimate the altitude. One day while doing this I decided that because the car was closed up the pressure inside might not be equalizing quickly enough during the rapid ascent; I opened the window and thought I observed a spike in the elevation profile. This is again something I want to investigate further, but haven't come to any firm conclusions.

As you observed, the Garmins restart the averaging every time you average. But this is a better approach anyway; just mark and average a new waypoint each time you want to make a measurement, and average them offline; the timestamps in the waypoints give you a record of when you made your measurements, and you can get a feel for how much variation you are getting from measurement to measurement.

You can open a second instance of MapSource and copy/paste the desired waypoints there, then delete them from your working file, and return them later. It would be nice if the display option in the Waypoint Properties window had a "none" option, but it doesn't (but if you have several you want to hide, deleting and pasting back later would be faster anyway). In playing with this, I just noticed that if I select "symbol" in the display option MapSource still displays the symbol and name; I don't think I've upgraded to the latest version of MapSource, so this may be a bug they have corrected.

After reviewing some tests I made about a year ago, I have to retract my statement about Garmin's use of a simplistic 1/sqrt(#samples) reduction in estimated error. I'm not sure precisely what they are doing, but the results are not as dramatic as you would get with a 1/sqrt reduction.

You should also suggest that they return at different times of the day, since the constellations at a given location pretty much repeat every 24 hours. Regarding the achieved improvement in accuracy with averaging: I don't know what your algorithms for the PN-20 are, but I'm pretty sure the Garmins reduce the accuracy by something like 1/sqrt(number of samples) during averaging; this would be correct if the samples were uncorrelated, but that isn't the case for samples taken over a short period of time. (They may not be doing quite that, but my feeling is that their reduced error estimates are too optimistic.) It's good to see a manufacturer come online and interact with customers this way. While I am still a committed Garmin fan (their customer support is outstanding) they tend to standoffish and noncommittal about the workings of their products. The next time I upgrade I will definitely be looking at the DeLorme products, along with the Garmins.