OGBO

As I noted in another thread, flux gate compasses like the one in the 60CSx are easily decalibrated by magnetic fields like you find around the "modern" car electronics (my former Ford Explorer was really bad for my 60 CS and CSx and the Suunto "wrist computers" in the family for decalibrating the compasses). A simple baseplate compass ($10) never needs recalibration, plus is not as picky about being held precisely exactly steadily level. Power lines (high voltage particularly), radio transmitters (like your cell phone, an FRS radio, or a ham radio handheld), and other sources of magnetic fields will also decalibrate the compass, as will a static discharge from shuffling across the carpet on a dry day.

The flux gate compass suffers from the same problem that many of the flux gate compasses in small electronic widgets do (including the Suunto "wrist computers") - they lose their calibration fairly easily from such things as being in a magnetic environment (near high voltage power lines, from RF radiation from being held near cell phones, FRS radios, ham radio gear, and even the control computers in certain cars, like the Ford Explorer I used to have), and even sometimes static electricity discharge nearby (like the zap you get on a dry day sliding out of the car or shuffling across a carpet). Besides which the ones in Garmin "S" GPSRs (60CS, 60CSx, 76CSX, etc) chew up a lot of battery real fast (leave the compass turned off and just get a $10 baseplate compass). A quick way to check on whether you need to recalibrate, if you insist on using it, is to hold the GPSR as level as you can and rotate it (horizontally, of course) back and forth through 90-180 degrees. If the card is "sticky", it needs recalibration (same thing shows up on pocket electronic compasses and wrist computers with compasses in them, like the Suuntos). This is a real pain, of course, if you are in a blizzard or dense woods or anywhere else you need a compass heading in a hurry, since it takes a couple minutes to do the recalibration. But, you should always carry a pocket compass with you in the woods and hills (and blizzards) anyway - they never need batteries and never need recalibration. As already mentioned, Garmin does not allow shutting off the barometric altimeter. The altitude shown (except on the calibration page or the satellite page when you select "GPS Altitude") is always the barometric altitude, which can be way off. As you were already advised, you would be better off returning the 60CSx and getting the 60Cx instead - longer battery life and fewer other problems.

Did you have the unit display that before you ran the Webupdater, to verify that it was still there? IIRC, some who have experienced a similar problem have reported that the unit will show Version 0.00, I think for the chipset firmware, when it happens. It seems that somehow the firmware gets erased. I suspect that was me, since I reported here that was what happened to me during an Antarctic trip (among other strange weirdities with the barometric altimeter). I have had the blank satellite page under some other circumstances as well, though turning off and back on has always (to date) cured that problem. In each of those cases, the firmware version has been there, so there is something else going on. But, due to the strange behavior of the barometric altimeter under certain circumstances that I encounter fairly often in my particular set of usages, I recommend strongly against getting the "S" versions of Garmin GPSRs.

Color screens on PDAs, GPSRs, cell phones, digicams, etc etc are pretty poor in direct sunlight, including TFT screens. Some monochrome and grey scale screens are ok. Professional photographers got tired of this some time back, so there are several devices available at your local high level camera store or on line at a number of the big dealers to solve this problem. The one I am using for my various color screens is a Hoodman HoodLoop. Basically, this is like a loupe (the magnifier that people used to use to check their slides), but with opaque sides to block the bright sunlight. It is sized for the typical DSLR LCD, but you can just move it around a little to view all parts of a PDA screen. They are pricey, but well worth it if you take a lot of photos and want to check out the stored images. Or if you have one of the typical P&S that have no optical viewfinder. Or, of course for looking at the color display on your GPSR.

That depends on your point of view. As one trained first in astrodynamics and having spent time arranging constellations, geometry dominates all . So my goal was reducing GDOP first and foremost. It was only later that I had to worry about the folks who kept putting in outdated ephemerides, building less than perfect clocks, and other practicalities. And then I had to re-learn general relativity (20 year gap from coursework). It's like looking at orbits from the force standpoint vs the energy standpoint - same result in the end.

As Grasscatcher said, in a word, yes. Problem is that the manufacturers (as usual) implement averaging differently (and change with generation of unit, too). Garmin has an explicit averaging in some of its units. Magellan has "automatic" averaging in some of its units (pause at a location for more than a few seconds and it starts averaging - some older units allowed turning "auto" on or off). Main thing is to be sure you average long enough. One minute is really too short (60 samples on the Garmin units that display the count). 15 minutes is generally reasonable. It seems best if you let the unit sit for a minute or two before starting the averaging, and certainly set it down at the spot you want marked (I've seen a few people wandering around while "averaging" - seems intuitively obvious to let the unit sit in a fixed location, but still, some folks ....)

As Grasscatcher said, in a word, yes. Problem is that the manufacturers (as usual) implement averaging differently (and change with generation of unit, too). Garmin has an explicit averaging in some of its units. Magellan has "automatic" averaging in some of its units (pause at a location for more than a few seconds and it starts averaging - some older units allowed turning "auto" on or off). Main thing is to be sure you average long enough. One minute is really too short (60 samples on the Garmin units that display the count). 15 minutes is generally reasonable. It seems best if you let the unit sit for a minute or two before starting the averaging, and certainly set it down at the spot you want marked (I've seen a few people wandering around while "averaging" - seems intuitively obvious to let the unit sit in a fixed location, but still, some folks ....)

You really believe people read disclaimers???!!!! "Read the manual? Read the manual? What manual?" or "We don' need no stinkin' manual".

Ummm, GPSlug, DOP is a multiplier that gives you the geometry effect of the satellite configuration as seen by the receiver. One thing it is telling you is whether you need to come back another time when the geometry is better - which is of little concern to the cacher or when driving your car (can't do anything about it other than try again later). It is of importance when mapping or other survey activities. It is NOT the 1 sigma error for unit range errors. But that discussion is beyond the scope of not only the thread, but GC Forum discussions generally. You are correct that DOP is only one component of the total error budget for a given location and time. Whether it is useful or not depends on your application and whether you know how to use it properly. The problem with Garmin refusing to say what their version of EPE really means is, first, you can't really judge what kind of error you have other than good/bad/indifferent. Which is ok for 90% of the use of the typical consumer unit (yeah, yeah, if I need to know, I should - and do - use a survey-grade unit). Too many users seem to believe that their target is always going to be within the EPE distance of where the GPSR says they are located (go back to the original OP's question for an example). Too few people understand probability well enough to understand what "1 sigma" or "2 sigma" means, or even what "50% probability" means. WAAS has 2 major components - the satellite errors (clock, ephemeris, and some other errors in the individual SVs) and the atmospheric errors (limited in usability to within about 500 miles of the reporting stations, which are only in the US, meaning that they are not applicable in much of Canada, nor in the rest of the world, though for those GPSRs that also pick up the EGNOS SVs, the correction messages are applicable in areas covered by the EGNOS stations). The satellite-specific corrections are applicable anywhere the GPSR is located, while the atmospheric corrections are only applicable within the areas covered by the observation stations. One reason errors with WAAS "on" happen is when outside the area where the atmospheric corrections are applicable. Garmin has acknowledged this and has suggested turning WAAS off when outside the areas where the reporting stations (WAAS and/or EGNOS) are located. Using the atmospheric corrections outside the area of applicability can indeed increase the error circle, which is the reason for Garmin's advice. Then again, as long as Garmin doesn't say what their version of EPE really means, that's a moot point. Just stick with it saying good/bad/indifferent and forget about it being quantitative. Just remember in any case that the position indicated is not exact, but only within 3 to 30 meters, most of the time being within 5 or 10 meters, but not always.

Well, they didn't have a cache at Patriot Hills or on top of Mt. Vinson, which are much more interesting locations than the South Pole. When I do the Last Degree ski tour in a couple years, I will visit the Pole as well. Besides, I locate caches, I don't "find" them. But my 3 (or 5) farthest actually visited so far (from SFBay Area) are GCB0D5 (Farthest Southern Cache, a virtual in Punta Arenas. Chile, 6963.9 mi), GCGETW (Karibu! - You Made It! - virtual at the summit of Kilimanjaro, 9723.6 mi), and GCBD7C (Murano Island a nice traditional in an interesting place 6044.2 mi), or I could substitute GCJM15 (Vogalonga Venezia - a traditional in Venice, Italy, that was missing when we were there, though we were at the location while it was disabled 6045.9 mi) or a beautiful virtual GC7BFF (The Snail, in Venice, at 6044.8 mi). There were at least 3 cachers who were at GCGETW the same day I was there (this past Christmas Eve Day, 2 of who were also from the US).

It's 95%, according to Garmin documentation. But I cheated. I actually looked at the manual. Are you sure you are reading the manual correctly? For my Summit HC, the Specifications say the accuracy is <10 metres 95% typical with WAAS off, and 3 metres 95% typical with WAAS on. This is presumably based upon actual field testing and theoretical considerations, etc. However, this is not necessarily the same thing as the Accuracy figure which the unit will display in real-time. While the unit can self-interrogate the quality of signals it is receiving, and look at the disposition of the satellites to determine whether a good fix is theoretically possible or not, it has no way of knowing for sure what the real-time accuracy is. The figure it displays is just an estimate, and it is generally accepted to indicate that there is an EQUAL probability that the error is GREATER or LESS THAN the indicated EPE. http://gpsinformation.net/main/errors.htm Hope this heps! Used to be that GPSRs (except Garmin) displayed the DOP numbers. This is Dilution of Precision, which is the extra error added (actually multiplied) by the constellation being used. Basic idea is if the satellites being used are all clustered in a small part of the sky, you will have a bigger error budget than if they are well-spread. DOP is different for horizontal position than for vertical (altitude). A lot of units even used to display HDOP and VDOP as well as DOP (the total). If you take all the sources of error (clock errors, ephemeris errors, atmospheric errors, etc) into account the horizontal error budget under ideal conditions is just what the manual says - 10 m without WAAS, 3 m with WAAS, 2 sigma (i.e., 95%). This was all too complicated for most people (still available on survey units), so the consumer units dropped the DOP display and started showing "error", "position error", "EPE" (= estimated position error) or some such term. Problem is, each manufacturer has its own version of "error". Not only that, but the displayed error circle on the map page and the EPE number do not always agree (my various Garmins are especially inconsistent, but several of my Magellans also show discrepancies). I have asked the tech people via phone, email, at trade shows, and in person, and never get more than a mumbled promise to look into it. Garmin's response to "what does your EPE really mean?" has always been "trade secret, can't tell you". Soooo, the basic rule is - treat the EPE number and the circle on the map display as very rough qualitative (not quantitative) guesstimates of the 50% error circle and recognize that the actual location could be spot on, shifted systematically (due to multipath in canyon situations, esp urban canyons, and the EPE calculation does not indicate this), off by 2 or 3 times the EPE, or anywhere in between. It is just telling you that the present indicated position is "good", "bad", or "sort of ok". I see times where I can walk up to a position (like a geocache) and zero out right on top of the container, and other days going to the same location that the indicated zero is 50 meters away, both for fully in the open and for challenging canyon/canopy situations, with the EPE saying it is 3m. But most of the time with the 60CSx (since that is the unit in question), even in challenging situations, it gets me within 3 meters. Then there are those days when the constellation is terrible and the terrain/vegetation is horrible and I want to just put the unit away and go by instinct (or Google Earth or USGS map). You just have to use the unit a lot and get a feel for how it behaves on different days. Oh, yeah, it gets worse when the batteries are getting low, and Garmin just keeps displaying a tiny error circle, oblivious to its inaccuracies.

To clarify the serial interface is part of the NMEA standard as I undertandit. That would mean that if you hooked up a USB to serial cable to your GPS it would combine with the NMEA mode on the GPS to be the real dea. But I could be wrong. Now that I think about, NMEA is designed to be serial (uses the same voltage levels). So I think that you are correct. I know that my radio and various other equipment that I connect my GPSr to are default serial. I do know that most of the new USB-based Garmins have dropped NMEA as an option. Yeah, but ... USB = "Universal Serial Bus". The NMEA data protocol (leaving aside the question of the voltage levels and the automatic transfer speed detection in USB vs having to set the bit rate in old-school serial) is still usable. The USB/Serial cables that you can readily buy work in the upload direction (going to the computer, which is effectively going to the USB-B end), but there are USB to Serial converters available if you go to the right website. Anyway, I have been annoyed at the number of new GPSRs that use USB connectors only, since my main DSLRs only provide a Serial connection (I have used one of the converters, but that's Yet Another Thing in the cabling chain, and is way too awkward and kludgy for most use.

Since I don't really do geocaching ... tracking my bike rides and training hikes tracking my actual route when doing orienteering competitions (the unit stays tucked inside a fanny pack, not used for navigation) navigating to various places (in a number of different countries) in car and on foot tracking my location and route during climbing expeditions and backpacking trips tagging digital photos (my DSLR has a cable connection to add the tag to the Exif file attached to the image) occasionally in S&R operations (thankfully this is not too often) routing and progress following on long cross-country drives (sometimes take caching breaks along with the food and rest stops) A couple times to find a repair garage for the car when a minor problem developed on a long trip, halfway across the continent sometimes in a new town to find a non-fast-food restaurant (sometimes find the info in the GPSR is not up to date, too). routing the fastest way back to the airport in a rental car

If I understand what you are saying, you are worried about variations in the displayed altitude on your 60CSx when it is in a fixed location. The other posters have basically answered your question, but not very clearly. First, the 60CSx (and other Garmin "S" GPSRs) has a barometric altimeter. "Barometric" means that it uses the pressure of the air to measure the altitude. As you probably know from watching the TV weather reports, air pressure changes with the weather. It also changes on a daily cycle, and even from minute to minute. To get a moderately accurate altitude reading from a barometric altimeter, you have to calibrate it at known locations (places that are well-surveyed reference points, determined by the government surveying office, such as the US Geological Survey or US Coast and Geodetic Survey, or similar organizations in other countries). The 60CSx displays only the barometric altitude, and not the GPS-derived altitude. It uses the ICAO Standard Atmosphere Table to relate the pressure measured by the barometer sensor (the "S" in 60CSx) to the altitude, plus the calibration you feed in. There are 3 ways of calibrating, as you have discovered - a known altitude, a known current barometer reading (get this from the local airport or weather office), or use the GPS-derived altitude (easiest to use in the field, and sufficiently accurate for almost any use). Barometric sensors are generally only accurate to 0.01 inch Hg (originally barometers used a column of mercury, Hg is the chemical symbol for mercury, in a tube to measure air pressure, with sea level air pressure supporting a column of mercury about 30 inches tall). As a rough rule of thumb, air pressure drops by 1 inch per 1000 feet of altitude. So, barometric altimeters are generally good only to the nearest 10 feet or 3 meters (the number Garmin specifies). Since the numbers are rounded off, you will see the reading flickering up and down by 10-20 feet (3-6 meters), all the time. There is no way with Garmin's "S" GPSRs to make them display the GPS-derived altitude in the display all the time. You can see the GPS value in the data window by pressing "menu" and selecting "Show GPS altitude", or when calibrating the altimeter. Otherwise, it is only the barometric altitude, and all the fluctuations that will show. In short, what you are seeing is normal. Don't worry about it.

julian, I think we are on the same page now. As for what the display jumps to when you set an elevation far too low, I suspect that it is the altitude of the absolute pressure. And I am now suspecting that it is not affected by the latitude as I had originally guessed. What I think is going on is this - If you set the altitude too low, you are telling the unit that the absolute pressure is higher than the barometric sensor is measuring. It does not matter whether the calibration is from "known altitude", "known barometer", or "use GPS-derived altitude". As long as the pressure actually measured is no more than a certain amount less than the value set, that is the altitude set is more than a certain amount lower (your guess of the Dead Sea is probably a good one), the displayed altitude will be happy. If you set a higher altitude, meaning that in effect you are telling it the "real" pressure is lower than what it is measuring, the algorithm is happy and won't switch to the barometric altitude. But if the difference is more than the amount designated, the unit will switch to the ICAO table value for the measured absolute pressure and auto-calibrate from then on (if autocalibrate is turned on). This would explain (1) why there is no switch when the altitude is too high (you might be in a pressurized cabin of a plane) and (2) why the switch shows up at ground level when you are in polar regions where the pressure-altitude relation is substantially different from the lower latitude relationship (that is, the pressure at a given physical altitude is substantially lower than the Standard Atmosphere Table gives). So what I suspected was a latitude effect programmed into the GPSR is not that at all, but is in fact the physical effect of latitude on the atmospheric lapse rate. This would explain why I did not see the switching on Denali (the thinning of the atmosphere is not great enough at the 60 deg latitude of Denali to trigger the switch, even at the summit), but do see it on Mt Vinson (the thinning of the atmosphere is great enough at the 80 deg South latitude of Vinson to show up as a large enough lower pressure difference to trigger the "correction". There was a similar problem some years ago with Garmins (but not Magellan, Trimble, or Lowrance) where Garmin GPSRs would not show altitudes below sea level. Their lowest altitude displayed (and it was a GPS-derived altitude) was 0. Garmin was a boating and aircraft instrument company at that time, so "no one" of their customers would ever be below sea level. Those of us in California who would go to Death Valley or the Salton Sea complained to Garmin for several years before they started allowing altitudes below sea level. By the same token, I guess they are right - there are probably only a few hundred people in the world who would notice the problem with the displayed altitude because they are in one of the few mountain ranges in the Arctic that are high enough or in the mountain ranges in Antarctica or on the South Polar Plateau, where the effect also shows up. Still, how hard can it be to allow showing the GPS-derived altitude in the display window (rather than having to search it out as at present), or to allow calibration of, say 2000 meters lower than what the absolute pressure says (that would cover all surface locations, though not aircraft flying in polar regions).

Somewhere (I thought it was in this thread, but don't see it right now), possibly somewhere else on the internet dealing with this or a similar question, I noted that when averaging a waypoint, the altitude saved for the 60CSx is the GPS-derived altitude, not the barometric altitude. This implies that the the displayed 2D location is derived using the GPS-derived altitude (the only sensible thing to do), not whatever the barometeric altimeter is displaying (no matter how calibrated and no matter how erroneous an offset). This explains why the experiments you are doing do not seem to be affected by whatever you do to the barometric altimeter setting - the unit is NOT using the barometric altimeter for position calculations at all, only the GPS-derived value, no matter what the display shows (In other words, Garmin is not letting you see what is really going on behind the displays). The way to see this is to offset the altitude (which is the barometric altimeter) by some large amount, mark a waypoint then go to "average" and watch. This is also the explanation for the weird EPE circles compared to the displayed position error. Garmin has always been very secretive about the meaning of their "position error" - not saying they are the 1 sigma, 2 sigma, or whatever error circles, not saying what the DOP of the constellation configuration is, or much of anything else. "Just believe and accept what we let you know". By the way, you say the Vista does not do what the 60CSx does when offset by a large amount. Were you careful to set the altitude calibration ("Known altitude" setting) to a large amount below your actual altitude? In other words, if you are close to sea level as my house is, did you set the altimeter to minus 2000 ft or some other value a couple thousand feet lower? Or did you forget the minus sign? The 60CSx behaves differently for altitudes much lower than for those much higher, as far as the autocalibrate and averaging are concerned.

Try this - Go to the Calibrate Altimeter window. Select "Know Correct Altitude?". Enter an altitude at least 2000 ft lower than your actual altitude and select "OK", and when it says "Successful" enter "OK". Then watch the altitude window (it helps to start with a page that has an altitude window, like the trip altitude profile where you have set a window to show altitude. Even if you have "autocalibrate" turned off, you will see the altitude reset (probably to a slightly incorrect value).

ONly time for some brief responses - Discussion with the Garmin tech folks started shortly after I got back from Antarctica (Jan 2007) and continued until sometime in Aug 2007, when I gave up on getting an informative or rational response. You generally will not see the barometric altimeter update unless you watch the altimeter continuously through a couple of full cycles. I saw it in Antarctica on my 60CSx and on a couple of other people's Vistas and 60CSx's, because it is so obvious under the high latitude/high altitude conditions. In general, if you set the barometric altitude with the "Do you know the correct altitude?" option at lower 48 altitudes/latitudes, the offset remains fixed (even if you set the altitude too high by 10,000 ft - recall the over-ride I described happens when the barometer reads a pressure that is too low by a large percentage compared to what it expects from the GPS-derived altitude, and apparently only at high latitudes and high altitudes). Yes, there is a jump in 3D position (both altitude and lat-lon) when one of the "best 4" satellites is dropped and replaced by another visible SV (even when the new one is part of the "over-determined" group). Lots of reasons for this, but not enough time or space to go into it now. You cannot place the current (last 4 or 5 years' models) of Garmin (or some other manufacturers) GPSRs in a true 2D mode. Even if you set the barometric altimeter to some wildly different altitude (via the "do you know the correct altitude" selection), the unit will show "no fix" if you have only 3 SVs (which you have to be stuck at for true 2D, which means you are locking the altitude). If you try to set a mark when you have 3 or fewer SVs (say, right after you turn the unit on), you get a warning message ("Do you want to proceed anyway?" which you might want to do if entering a known lat-lon from a book or map). One way to see this is to offset the altitude by a large amount (while you do have a fix), press "Mark", then select "Average" and look at the altitude - it will be averaging on the GPS-derived altitude, not the off-set altitude. If for some reason you want the saved waypoint to be at a different altitude, you have to edit the altitude in the waypoint. So your observation of accurate 2D horizontal position is really a 3D position. I haven't been back to Antarctica and won't be until at least 18 months from now (or more likely a year beyond that), so I don't know if Garmin has made an appropriate change in the firmware. But there is no mention of it in the list of changes for the last couple of releases. Besides, the 60 CSx and Vista, etc models are "obsolete" now. Who knows if the Colorado or whatever the successors will have the change. Garmin won't tell us about bugs that were fixed between models (except for the usual "NEW! IMPROVED!" comments - yeah, "improved" how?)

In my discussions with Garmin, they said basically the same thing julianh said, except they gave me the update intervals (basically, at frequent fixed intervals if the unit has a 3D fix, the barometric altimeter is re-set to the GPS-derived altitude). There are several problems with that approach. First, referring back to my discussion of the problem in polar regions, if it really worked as Garmin described, the altitude display should be relatively in agreement with the surveyed altitudes. But it is NOT, at least in latitudes above 70 deg. Second, if it worked as described, the units with this "feature" would not show the behavior I observed of displaying momentarily the GPS-derived or manually set altitude, then within 15 seconds (yes, I timed it) switching to the purely barometrically-derived altitude (yes, it matched the measured absolute pressure, which I was simultaneously measuring). What really happens is that the Garmin algorithm uses the criterion that if the barometric altitude is greater than the GPS-derived altitude by more than a certain amount (roughly 1000 feet if the absolute pressure is less than the equivalent of 7000 ft, meaning lower pressure than that in the ICAO Standard Atmosphere Tables), the barometric value over-rides the GPS-derived value, thus losing the calibration, whether manual or automatic. Of course, this means that this will have no importance for most use in most of the land masses of the Earth except for Antarctica and northern Alaska, Canada, Scandinavia, and Siberia. As also pointed out by others, the displayed altitude shows anomalies in mountainous areas in windy conditions, particularly in the area of passes (due to Venturi effect). But there are anomalies in the GPS-derived altitude as well. The displayed position (3D, meaning lat/lon/alt) is part of the full 4D solution that the unit derives iteratively. If the horizontal position is off (potentially, and by my observation in certain locations) because of multipath, the altitude will also be off - all 4 positions (lat/lon/altitude/time) are interlocked in the solution. The time solution will not be noticed by the user of consumer units, since the time display only shows the nearest second at best, and the deviations are of the order of nanoseconds. The position equivalent is close to one foot per nanosecond. In older units where it was possible to lock into a 2D display (in the case where you "know" the altitude, such as on the open ocean), I ran tests on the horizontal position error induced by entering erroneous altitudes (and later by running through simulations). As a rough rule of thumb, it turns out to be roughly 1 km horizontal error for 1 km offset in altitude (not surprising if you know how the solutions work). In other words, it works both ways - error in altitude (perhaps from using the barometric altitude in polar regions) induces horizontal error, and horizontal error (perhaps from multipath) induces altitude error. Of some comfort, though, the Garmin techs I spoke to stated that the solution is obtained using the GPS values, not substituting the barometric altitude in the computation. I will also note that the early units that displayed barometric altitude allowed displaying either GPS-derived or barometric altitude. So it was a case of eliminating the choice of displaying the GPS-derived altitude

The barometric altimeter in the 60CSx (and other Garmin altimeters) has got to be my biggest complaint with them. After a bad experience with the 60CSx in Antarctica, I had a series of exchanges with the Garmin tech folks and never got a satisfactory response (I'll describe the problem below). As long as you have a 3D fix with a reasonable constellation (SVs spread over the satellite display), the accuracy of the GPS-derived altitude is as good or better than the mapping accuracy of USGS maps (refer to the USGS mapping website for the accuracy standards - basically 1/2 contour interval at surveyed points, which means +/- 20 ft for most quads and could be much more in many areas, vs the GPS error budget of 1.5 x horizontal error, or +/- 30 ft 1 sigma). If you derive altitudes from the DEM files or do stereographic tracing (as done for the contour lines), you can be off by much more. Obviously if your estimated error is very large, due to a poor constellation view (DOP, to remind the old-timers, which used to be displayable), your altitude error can be large as well. Having said that, the basic complaint is that the 60CSx displays the barometric altitude all the time. There is no option for displaying the GPS-derived altitude in the window on any screen. You have to recalibrate frequently, especially in mountainous terrain. I have seen many times an altitude set at, say, a lake with a well-derived lake level altitude, then climbed up a few thousand feet to a nearby peak, only to find the altitude displayed off by 200 or 300 feet, then descend back to the lake and find it displaying the lake level altitude. This is a peculiarity of all barometric altimeters, including my favorite pocket Thommens - the real lapse rate (altitude vs pressure) is frequently different from the Standard Atmosphere tables. There are all sorts of other error sources for barometric altimeters, such as change of pressure during the day, or due to frontal passage, or even standing on the windward vs on vs leeward side of a pass when the winds are strong (venturi effect). Now you can look at the GPS altitude without re-calibrating. Go to the Satellite page. Push the menu button. Scroll down the menu to "GPS Elevation" and push "Enter". The displayed altitude is not continuously updated, but is instead the computed altitude at the time you pushed "Enter". The Antarctic incident - It is widely stated that at high latitudes (more than 70 deg north or south), the absolute pressure at a given altitude is less than at the same physical altitude above Sea Level. I have confirmed this by taking the absolute pressure, for example, in ascending from Mt Vinson Base Camp up to High Camp, then comparing the surveyed altitude (derived during the Project Omega mapping study of the Sentinel Range) with the altitude the absolute pressure would indicate using the Standard Atmosphere tables. At High Camp, the absolute pressure corresponds to an altitude about 1500 feet higher than the surveyed altitude. With the 60CSx, if you attempt to set ("calibrate") the indicated altitude to the surveyed altitude, within a few seconds, the displayed altitude switches to the barometric altitude as you would get from the ICAO Standard Atmosphere Table, whether or not "automatic recalibration" is shut off. This happens whether you choose "I know the altitude", "I know the barometer setting", or "use the GPS altitude", as long as the barometric altitude is more than 300 meters or so higher than you set it, and apparently above some minimum indicated altitude (Garmin tech was very reticent on this point). Garmin's response to my suggestion that an option to display only the barometric altitude was to dismiss it as being of interest to a tiny number of users, probably no more than a dozen.

What version of Windows are you using? If you are using Windows XP, you should not only have installed Service Pack 2, but also a patch from Microsoft that relates to running a number of applications since MS did an update in early April. I would have thought they would have repaired the "auto-update" that had the glitch by now, but they haven't. Search the Microsoft knowledge-base site. or just go to support.microsoft.com/KB/935448 I first ran across it for my Suunto X6 software, but it turned out to affect a number of other applications that interface with electronic widgets. IIRC, there is a second Garmin software patch that isn't referenced when a similar problem cropped up. Search the Garmin update list. No guarantee that this is it, since I haven't been using my Topo East or West since before April.

There are several problems with the built-in electronic compasses and the built-in barometric altimeters. The first one mentioned by several already is that they are battery hogs. A couple people suggested turning them on only for a brief period when you actually want to use them. Problem with that in Garmin's case is that the barometric altimeter is always on - you cannot shut it off in the 60CSx, 60CS, 76CSx, 76CS, the new Vista, etc. In the case of the compass, the drain on the battery is astoundingly huge. I find that turning it on even for a few minutes puts a huge dent in battery life. Second point on compasses is that even an inexpensive baseplate compass is easier to use and more precise than the built-in compasses (Suunto, Brunton, and JWA's Silva all have basic baseplate compasses for about $10). They never run out of battery and take only a few seconds to set the direction arrow (setting the equivalent on an electronic compass takes 20-30 seconds). And yes, I have a 60CSx, a Brunton electronic compass, and a variety of orienteering and survey compasses, so I have a good basis of comparison. If you carry the baseplate compass around your neck on the supplied lanyard, it is always ready to hand, without even switching screens on the GPSR. Another point on compasses is that a standard magnetic compass does not require re-calibration, which electronic compasses do on a frequent basis. I have had to recalibrate the 60CSx and the compass in my Suunto X6 when navigating in whiteout blizzards and fog - inconvenient to say the least. Thankfully, I have learned to recognize the signature misbehavior of a de-calibrated electronic compass quickly. The easiest solution is just forget about the electronic compass and use a real compass (the electronic compass in my plane had an automated recalibration, but I still had the back-up regular magnetic compass, as is required). Still another point is - look at the price difference between the sensor and non-sensor versions of GPSRs. The difference between the 60Cx and 60CSx, for example is far greater than the $10 for a simple baseplate compass which is far better. The OP didn't mention the barometric altimeters, but this has come to be one of my greatest complaints in those Garmin GPSRs that have them. Garmin has them turned on all the time - there is no way to have the 60CSx and 76CSx, for example, show only the GPS-derived altitude. If the "calibrated" altitude shown by the barometric sensor is within 1200 feet, the Garmin units will not autocorrect to the GPS-derived altitude. This means that if the barometer reading shifts by, say, 0.3 inches from day to day (equivalent to 300 feet error), the Garmin units will happily display this erroneous altitude, unless you go through the recalibration procedure. Since the GPS-derived altitude is within 1.5x the horizontal error estimate of the true altitude, the GPS-derived altitude will rarely be off by more than 30 feet, and usually much closer than that (remember that the USGS accuracy specification for 1:24k maps is 1/2 contour interval, so about 20 feet on most maps, putting you in the same ballpark as the maps). To have the altitude displayed on a Garmin "S" unit, you have to recalibrate the altitude to the GPS-derived altitude (3rd choice on the menu) or be at a known, surveyed altitude point on a frequent basis. Worse (for someone like me who travels to polar regions frequently), since the atmospheric pressure in polar regions (above 70 deg latitude north or south) is significantly lower than the surveyed altitude would indicate, the Garmin "S" units display an altitude that is significantly different from the surveyed altitude when you get above 7000 or 8000 feet. At those latitudes and altitudes, the difference between the GPS-derived altitude and the pressure altitude is greater than 1200 feet, so the Garmin units "feature" of auto-calibrate resets to the barometric value within a few seconds of attempting to set to the surveyed altitude or to use the GPS-derived altitude. At the 12,100 foot High Camp on Mt. Vinson in Antarctica, for example, the 60CSx insisted on resetting to 13,500 feet and would not accept the correct altitude. Ok, that doesn't affect most people, but it is a real flaw.

Hynr is partially correct that the original data come from USGS. They also come from a couple of other US Government agencies. These days, most of the GPSR manufacturers buy their data from NavTeq, who start with the government data, but do a bit of editing and compression. Second point, though, is how the data get displayed. Unlike software such as National Geographic's Topo! and the 1:24k maps in Delorme's Topo USA, the hypsographic and political displays on GPSRs are NOT scanned from the original USGS engraved plates (with the exception of Delorme's new GPSR). "Political" data are the line data, such as state and county boundaries, city information, and the road and similar information. They are drawn on the fly from line files that are similar to (but not directly) the USGS line files. The big difference is that to vectorize them in a form that fits into today's GPSRs, a fair amount of cutting of the list of points making up a line has to be done. On the engraving plates from which the USGS paper maps are printed, real humans cut the lines into the metal plates (with the aid of engraving machines), where in your widget, the lines (hypsographic, streams, roads, etc) are drawn point to point from the vector line file. That's ok for roads in rectilinear cities, where the town is laid out in a grid pattern, or for state boundaries where they are "straight" lines (they are really great circles or small circles on the surface of the Earth, but look straight in the tiny few-mile segments on the map). A third point is the way altitudes (or depths) are displayed for points, both on the GPSR maps and on the computer maps such as NatGeo's Topo! and Delorme's Topo USA. These are computed from a grid of altitude points (stored in the files as lat/lon/altitude). When you mark a point on the map, the altitude of that point is computed by interpolating the 4 points bounding the box in which the point lies (I mean on the map as it appears on the screen of your computer, not the GPS-derived or barometric altitude displayed by your GPSR). These grids come from the USGS DEM files (Digital Elevation Model). In some areas, the grid is 100 meters on a side, while in others it is 1 km or even larger. Over time, USGS has been issuing smaller grid spacings. When you run the cursor over the map, if that mountain peak happens to be in the middle of a square, the software will show it as lower than if the grid happened to place a grid point right on the peak (in some parts of the grid, there are supplemental points placed on important peaks and other locations). So some of the differences you are seeing in the 2008 version are due to more points used in defining the lines for contours, some due to finer grids of elevation data, and, yes, some due to updated surveys. I will have to say, though, some just plain baffle me - like the positions of some roads along coastlines that end up with the road running some distance off-shore. Well, no, the reason is that someone did not check on the points used to define the line delineating the coast and those defining the road to see if they were compatible. Unfortunately, mapmaking still has a large artistic component. Be grateful that the maps aren't still showing sea monsters in the water areas.

Ummm, having been bit by a rattler about that size, one thing I learned about pit vipers generally is that the young ones haven't learned to conserve their venom yet (the older ones will strike without envenomating as a defense tactic, saving the venom for their food prey). So you can get a significant amount of venom from the "babies" (or maybe the "adolescent males in full hormonal flow" and in their aggressive mode).

Already tried those. Competitive had sold their last one just a couple days before I called. The Core5 project is a good one, but the parts add up to double the msrp of the MC-35, and at this point I am too short of time to build a cable and trouble-shoot it.