nincehelser

For the past few days my son and I have been taking readings from a yellow eTrex (no WAAS) and a Vista (WAAS enabled). They are positioned so that WAAS reception will not be a problem. So far we have 16 pairs of readings over three days at various times. The two receivers have not been more than 3 meters different in either easting or northing (we're using UTM to keep the math simple), and that extreme has only happened twice so far. Usually they seem to be within 2 meters of each other. I'm finding this kind of suprising. That yellow eTrex seems to be performing pretty dang well for being older and not having WAAS. Just looking at the raw data, WAAS only seems more "confident" as far as the positioning goes, usually being about half that of the non-WAAS unit. George

In theory, yes. There is a polling function, so you don't have to train your llama to hit the talk button. Personally, I'd track my llama with APRS....if I had a llama....which I don't....but I just like saying llama. The RINO 120 has mapping ability. The RINO 110 does not. FYI: A one-L lama is a holy man. A two-L llama is an animal. A three-L lllama is a really big fire. George

That's because you already burned your money ahead of time. Sorry. Couldn't resist. George

There's the problem! Yes, the deer problem seems to be growing everywhere. Yesterday I was eating in the local Jack-in-the-Box, and saw about 20 deer across the 4-lane highway. I think that's the largest group I've ever seen. The restaurant manager had this funny gleem in his eye... This is in a formerly rural area that is quickly turning suburban. The deer are essentially surrounded by homes now...and there's nowhere for them to go. Something's gotta give. I like venison sausage, but I'm going to watch that Jack's menu closely from now on. George

It sounds normal. My son and I are currently comparing a yellow eTrex (no WAAS) readings with a Vista eTrex (WAAS enabled) for a school science project. We haven't crunched the data yet, but on the surface the numbers don't seem to be all that different. The only obvious thing that jumps out at me is that the WAAS unit seems much more confident in its measurements. I'll know more once we start graphing the data, but I'm suprised we're not seeing more of a difference between the two units. We're taking data over time from a single fixed point in an open area where the reception of the WAAS won't be a problem. George

Nah. I'm pretty sure it carries weight. Check out this link: http://www.kansashighwaypatrol.org/facts/e...nt.htm#whistles Or here: http://www.swdtimes.com/swdtimes/html/Dail...AY/oct22/03html It looks like the KHP must not know about their own study. George

I don't know about that study in particular, but I know others claiming the whistles work have been debunked. Some other research has shown that it isn't the deer whistles themselves that result in reduced accidents, but that it was just increased driver awareness about the deer problem. People who were buying and installing the whistles were just more safety-concious to begin with, and those forced to use them were just made more aware of the possibility of hitting a deer. If I remember correctly, the study installed some bogus deer whistles on some vehicles (the drivers thought they were real whistles) and the accidents went down. The drivers reported that they were actually seeing deer scared away. Since the whistles were fake, that result was just chalked up to better driver awareness. I can't say that's the final word on the subject, but I won't be convinced that they really work until my insurance company gives me a price break for having them installed. Does anyone have an insurance company that does that? Here's an interesting article on the subject. Make sure you read down to the bottom where it talks about the whistles, and what one guy tried in Arkansas. http://www.usroads.com/journals/rmj/9705/rm970503.htm George

I've gotten really wacky elevation readings on my Vista after turning auto-calibration off. If you don't do something to manually calibrate (like checking a benchmark or referring to topo map for alititude from time to time) who knows what it's using as a reference point? The simplest thing is just to keep auto-calibrate on. It periodically uses the GPS elevation reading (which isn't real accurate...about 2x the horizontal error) to calibrate the barometer. What you get isn't a highly accurate elevation, but it's in the general ballpark. The barometer can then inform you accurately of changes in your altitude for a short period of time, depending on how stable the weather is. For example, if I'm at the foot of a hill, I could take a barometric reading (point A). I then climb to the top of the hill (in a reasonable time) and take another barometric reading (point B ). From the two readings, I can fairly accurately figure how how high the hill is from point A to B, but I really don't know the actual elevation from sea level unless I'm comparing them to a known reference point. I don't recall the name of the explorer, but I believe this is the technique that was used to initially measure the heights of the walls of the Grand Canyon. If you really want to get a really accurate idea of your elevation, you probably need to refer to a topo map, and then cross-check it with your GPS. If your GPS can get the WAAS signals, that should also reduce your possible elevation error. If you keep auto-calibrate on, I'll bet you find your Vista will give you more accurate readings over more altitudes than your Casio. Trust your Vista. George

Nope. Don't need one. Don't want one. I've several altimeters I use in my rockets. I know how they work. It sounds like your Casio isn't very sensitive. Even a broken watch is right twice a day. Here's an example. Over the last few hours, the barometric pressure according to my weather station has gone from 975hPa to 979hPa (that's from about 28.8 to 28.9 inches of mercury). That's a difference of 4hPa. 1 hPa represents about a 10m change in altitude, so that's a change of 40 meters (more than 120 feet of alititude). That figure isn't unusual, and it fits in the range of your readings, so your Vista is likely correct. George

So what you're saying is that when a severe thunderstorm moves into your area, your Casio still shows the same altitude? If it does, it is broken. *ALL* barometric altimeters require frequent calibration because air pressure keeps changing due to weather conditions, and not just your movement up and down. George

C'mon. You must be the Dr. Bronner of Dr. Bronner's Soap fame? It's sure seems like I'm reading one of his labels. "All-One!" George

Please post your findings here, I would like to see what y'all came up with. Thumper Will do. We've just been taking reading for a short time, and my initial take is that I'm suprised how close the WAAS and non-WAAS readings are so far. Perhaps it will vary more over time as the sat positions change. Elevation readings seem the most erratic as would be expected, but I'm not sure how much the Vista's barometer is impacting that. I can't seem to figure out how to turn that feature off. I tried turning off "auto calibrate", but then the elevation readings were really screwy. If I leave it on, both elevation readings seem reasonably close to each other. One thing I noticed as the temperature is falling...both units are sitting directly on the concrete patio, and are getting kind of chilled (it's about 53 degrees F right now). The yellow eTrex display seems to be slowing down, while the Vista still seems normal. We started both units with fresh batteries out of the same package. This isn't exactly what we want to measure, however, so I put both units on a small plastic box to insulate them somewhat from the concrete. Update: I boosted the display contrast on the yellow eTrex substantially. Now it seems readable and normal. I've never had to do that before. George

Tangent, Secant, Cosine, Sine! 3.14159! I won't claim to have mystical technological knowledge yet unknown to the masses, but my son and I are planning to compare non-WAAS and WAAS readings this weekend as part of his school science project (6th grade level, so we're not going to be spending big bucks, time, or using extreme math). We're going to take several readings over time on a particular spot in an open area, where WAAS availability won't be a problem. I'm guessing that the WAAS data points should be clustered in a tighter circle than the non-WAAS readings. The thing I'm really interested in is how well the results compare to the "advertised" specs of a consumer GPS (in this case, the test units will both be Garmin...one with WAAS enabled, one without). George

On what do you base the "10 times more accurate", other than what that faulty article says? WAAS is advertised as getting you within 3 meters. "Regular" GPS reception today is said to be within 15 meters. From that I get a factor of 5, not 10. Even that assumes WAAS under optimum conditions, which often don't exist on the ground. George

I don't know how many times it has to be said, but apparently it isn't getting through. It depends on the particular cave, of course, but cavers do have to get "special permission" from those charged with managing the cave. The "if cavers can go there without special permission, so can geocachers" is a pretty weak argument. Unless a caving group own the land with the cave, they are at the cave manager's mercy on whether cave access will be granted or not. Cavers don't have a special pass that lets them into any cave they wish. It's up to the manager. If he/she thinks placing a cache will not cause problems, then they may allow it. It's that simple. Ask for permission from those in charge. If you're allowed, great. If you're denied, hide a cache somewhere else. There are close to a thousand caves in my two-country area. No one here feels it necessary to put physcial caches in them. George

Don't put too much stock in that article. It isn't technically accurate. I haven't heard of WAAS going global anytime soon, if at all. Much of the US doesn't even have redundant coverage (there are only 2 sats transmitting WAAS data), let alone the ocean blue. George

WAAS was designed for aviation, where aircraft generally have an unobstructed view to one of the two geo-stationary WAAS sats that is necessary to make the system work. One big advantage for aircraft is that it makes the elevation reading more accurate than it would be otherwise. On the ground, the view to those two sats is often blocked, making the system much less useful. If you're hiking on the north side of a mountain, for example, WAAS doesn't work as well, if it does at all. WAAS does draw more power, both electrically and computationally. It doesn't have a huge impact on battery life, but some people find their unit updates more quickly if WAAS is turned off. I leave WAAS off. I'm just not real impressed with its usefulness. It doesn't work much of the time, and any increased accuracy doesn't add much to hiking or geocaching. George

I doubt it. The digital portions (i.e. most of it) of your GPS pretty much swing one way or another. There is little middle ground. It either works, or it doesn't. The analog portions could be impacted by a changing voltage, but I very much doubt it is detectable without sensitive test gear. Alkalines slowly decrease in voltage over time. If there was a noticable decrease in accuracy over battery life, I expect someone here would have caught it by now. It would also imply that fresh alkalines would allow more accuracy than most rechargables, because of the voltage differences inherent in their chemistry. When the voltage drops low enough, all bets are off. Then your unit starts acting flakey. Accuracy is the least of your worries at that point. George

Rechargables are much more difficult to figure out how much life they have left vs alkalines. The voltage in alkalines goes down slowly over time. Rechargables have a voltage that stays fairly constant, but then drops sharply near the end of its charge. That means monitoring voltage alone isn't as accurate for the rechargables. It's even harder since you don't even know how much charge they had in the first place. More advanced battery monitoring software trys to take other things into account...essentially trying to estimate just how many electrons have moved through the battery. It's still hard, though, since you don't know how many there were to begin with. What you really need is some intelligence in the battery or battery pack. I think the 15-minute Ray-o-Vacs are an example of this. Each battery has it's own chip. I'm not sure if these somehow communicate with the charger itself. Personally, I think battery technology just isn't getting where it needs to be fast enough. I'm hoping small fuel cells will make an economical debut soon. George

That's true with NiCads. The NiMh don't require that though, and it makes no difference with them what level of charge is left in them when they are rechared. You also need to be careful with how deeply you discharge. In some situations, the polarity of the battery will reverse, which can be very bad news. NiMh is included in that group, so it is usually safer to keep topping it off then letting it drain down too low. George

That's not uncommon. Much depends on the capacity of the rechargables. Some can provide higher currents than others, and that makes a big difference depending on the power demands of the kind of device you are using. Also, rechargables self-discharge at a higher rate than disposable alkalines. It can be 3% to 5% per day depending on the temperature. If you leave a rechargable battery in a hot car for a few weeks, it will die (if not dead already) sooner than an alkaline in the same situation. George

It's the batteries. Some of it could be the LCD display, but the batteries are the bigger factor. Batteries operate via a chemical reaction. When they get cold, this reaction slows down. You may get the required voltage at a cold temp, but when your GPS really demands juice, the chemical reaction can't keep up the current supply demand. Thus it seems "dead". Warm the batteries and it should be fine. Temp does impact the LCD, but this is usually cosmetic. The internal electronics may be chugging along at full speed, but the display can't keep up. So it may *look* slow, but the internals are functioning normally. My problem is usually the LCD getting too hot, not too cold. But if the the whole unit is cold, both LCD and batts are likely cold, so you get a double whammy. However, changing the batts for warm ones will usually rememdy the problem alone. The type of battery chemistry is important, too. Some work better than others in colder temps (e.g. lithiums). George

Your biggest mistake was buying at Walgreens. I've found they are likely to carry old stock in several sections, and some things come off the "grey" market, or were someone else's over-stock. I would hazard a guess the batts you got were old and/or poorly warehoused. In any sense I'd complain to the Walgreens. That's not enough time, and the price is horrible in any case. I can easily get *fresh* big-name batts for 25 cents or less per when they're on sale at the local grocery store. Even the off-brands last at least 8 hours in my eTrex's. George

And there's that other problem trying to stop people from eating them George

That is true, unless you can figure out some abstract way to represent the numbers to make it utterly confusing. Like using unusual symbols to represent numbers, and make their relative orientation critical. Me, I'd just dis-assemble the cube and re-assemble. I used to know a guy in high-school who could solve the cube in seconds (the legtimate way). Of course, to do this, the cube had to be broken-in just right to handle his speed, and he used some sort of dry lubricant to make things slide easier. You could hand him a new cube, but it would take him a bit longer to solve (not much, though) because the cube was "stiff". I took one of his cubes (he had several, of course...a true professional) and swapped a couple of stickers so it would be impossible to solve. After about a minute he was real flustered, and realized something was "wrong" with that cube and threw it at me. We all got a good laugh out of that. George