Peregrine007

GPS doesn't use barometric pressure to determine altitude. I think you can get a GPS with a built in barometric type altimeter, but that's not GPS altitude. GPS uses the distances from several satellites to calculate the location of the receiver. I think it's a sort of doppler like effect (difference in time it takes a signal to get to the GPSR from various sat's) combined with traingulation. Anyway, atmospheric pressure will not effect altitude readings of a GPSR. Well, that's sort of right but not entirely accurate. GPSr's with a built-in barometric altimeter will give you a GPS altitude if you have a 3d lock, but it'll be wrong if you have only a 2d lock or if your GPS accuracy isn't all that good. That's where the barometer comes in. It will sense smaller differences in air pressure to give you a more accurate altitude. But your question about the ambient air pressure changing is a good one. In this case, you have some options. The GPSr's I've used with barometric altimeters (Garmin eTrex Vista and Garmin GPSMap 76S) give you some options. You can elect to have the barometric altimeter "auto-calibrate" - that is, it calibrates itself based on the GPS altitude when it has a good 3d GPS lock with a good (high) level of accuracy, and so the GPS altitude is quite accurate. If you then lose your 3d lock or accuracy, the barometric altimeter is more accurate as it can sense the small pressure changes and convert that into a rise or drop in altitude. If you know the precise elevation of your current position, or if you have a good wall barometer (that you trust) or have some other source of accurate ambient pressure, you can use either of these to manually calibrate your altimeter before you head out. I usually use the auto-calibrate mode, and after you get a good solid 3d lock (or better yet a 3d WAAS or differential lock) it gives amazingly accurate results. If you imagine that you're going for a hike up a mountain, but in the forest, you can have the GPSr auto-calibrate itself while it has good satellite lock on your drive to the trailhead, and it'll use the newly calibrated barometric altimeter to give you a good elevation during your hike. By comparison, if you did the same hike with a "regular" GPSr (no barmoetric altimeter), your GPS altitude would remain the same if you were hiking up a mountain but only had a 2d lock due to tree cover etc. This makes a big difference when you like to see your elevation profile on your track log after the fact!

My first GPS was a Vista, which I bought pretty much exactly one year ago. It's a great unit - small and light, it gives good fixes and I've never had any problems with it. I recently upgraded to the GPS Map 76S, and for the most part it's not really that much different. It has some extra features - mainly small things like the tide calculator, and the screens are a little more customizable in terms of how many data fields you want on each screen, and how large or small each field is etc. It will average a position over as long as you want to give it (when you're marking a waypoint, that is), and shows the estimated accuracy based on how long it's been averaging and what the EPE is for the duration. But, they both have pretty much the same major features - electronic compass, barometric altimeter, etc. etc. and there are even a few small things that I preferred about the Vista (relocating a waypoint to "here", which was useful to have a "car" waypoint that you could just reposition, etc.). The Vista is also considerably smaller and fits easier in your hand, especially when you're climbing loose rocks up a 7,285 foot mountain down in Death Valley :-D and you're concerned about falling on it or dropping it as you scramble down steep loose bits trying to get to plane wrecks. All in all, they're both really good units - the weak point of both of them is that the Canadian Mapsource maps leave a lot to be desired (although I've heard the most recent one is a major upgrade), and we still have no topo maps of Canada that can be uploaded (I really miss those after using the US topo maps recently!). Oh yeah, if you decide to go with a Vista, let me know - I have one for sale that's brand new (replaced under warranty)! :-D

Haven't you quit yet?

I heard we might expect more of those cold out-flow winds around the middle of the month, which might bring us more of the white stuff. Guess we'll find out!

Any altitude data that it has for waypoints isn't used to actually find a waypoint. Unless of course your cache is on a multi-story parking garage or at the top edge of an overhanging cliff etc. where it might prove useful to have that information. When you're at an actual site and mark a waypoint, it will store the altitude it currently has based on whatever the GPS is set up for at that time (i.e. barometric altimeter or GPS elevation, which may or may not be accurate depending on how long the GPS has been getting sat signals for and what the quality of those signals is like). Hope that helps!

No problem. Happy shopping! **** Geo 15 25 29 06 44 55 117 118

Ha - speak for yourself! **** Geo 66c

I know of at least one person who wouldn't mind taking over one of their jobs... ***** Geo 8 10 18c 81

I think you might be on to something! ***** Geo 88

If you're just referring to the EPE that your GPSr gives you, I don't think it applies to the elevation you're getting from the GPS system. That is, I think your 3m EPE is only for a 2d fix, and that the elevation you get from a 3d fix may not be accurate to the same degree. I'm not certain about how that works, so I may be wrong. Unless your GPSr has a built-in barometric altimeter, such as what you'll find on the eTrex Vista and Summit, GPSMap76S, and the Magellan Meridian Platinum, I wouldn't trust the altitude it's giving you. As far as I know, the altimeter on something like the Brunton Weatherstations works exactly the same as the ones incorproated into the above-mentioned GPS units. They all rely on subtle differences in barometric pressure to get their reading, although the ones built in to a GPSr will automatically calibrate themselves because they get approximate elevation data from the GPS signals. I'm not sure how the stand-alone altimeters work - you may have to manually calibrate them by giving them either current barometric pressure at sea level, or your current known altitude before you start your journey (you can also give this information to the GPS units so they can use that for calibration instead of GPS data). As for topo maps, the geology of our planet is changing - but not by a metre since some maps were produced in 1967 or whatever our oldest ones are for some areas. Worst case scenario (and assuming no massive earth-moving occurnaces!), you might move as much as a millimetre or two over a period of a couple of hundred years. I don't think even Roswell could measure that!

As much as that might seem like a viable and usable alternative, it's not practical. A quick glance at a map will show you that a down-town to down-town route would be a LOT of extra mileage, which translates to a very long travelling time for what is essentially a pretty short distance. BC Ferries announced a while ago that they were trying to make each run pay for itself, so that some runs weren't subsidizing others (as much as they had been in the past, at least!). If that's really a goal they plan on persuing, then your proposed route would be extremely expensive to operate and those costs would be passed on to the consumer. Huge costs would push more people to pay the relatively small difference to take a seaplane or helijet trip. As much as the idea may not be popular, travelling by boat is low-tech and somewhat passe. In our fast-paced world, I think more fixed-link options will be presented in circumstances like this one (an obvious example is the EuroTunnel). I'm not saying it's the best way, but many would argue it's the most viable.

I believe that TEAM KFWB GPS put a number tag on one of the ferries. One the people from the Island should be able to confirm this. ***** Geo 84B 98V Yeah, there might be one or two out there...

I don't remember what you're using for a GPSr these days ZZ (but I'm sure CG probably has a photo of it somewhere ) but my experience with the barometric altimeter in the Vista has been really good. I've checked it a few times at known elevations, and it's always given me numbers within 1m elevation. Even when "known" numbers aren't readily available, its altitiudes always match our topo maps. But yeah, those Brunton weather stations look pretty cool too! That's a few toys down on my list

I'm all in for some rock throwing - if we start at each end (with enough rocks) eventually we won't need the ferries anyways! Can't they do all this in the summer? At least the weather is more conducive to other transportation options (read: kayaking!). Sooo.... what's wrong with a bridge? I'd have no problem with a toll being the same as what the ferries are now - at least your travel time would be cut by about 3 hours! And, "ferry traffic" would be a thing of the past.... They say $5B would do it. Dear TEAM:

Hey ZoomZoom, I'll sell you my Vista

Garmin's eTrex models don't feature 'averaging'. The position will change slightly as you stand there, but the GPS will just think you're moving around. Many Magellans will start averaging as soon as you've stopped moving, and contrary to some posts above, the position accuracy WILL get better the longer you stay there. Try this out at a known benchmark and you'll see what I'm talking about. Some units, like the Garmin GPSMap76S, will allow you to start averaging when you like, not when you tell it to start. So if you get there and only have a few satellites, you can wait to get more sats before you start averaging. It will also place more relevance on positions it records when your EPE is best - that is, if you position for 2 minutes and the first minute it says your EPE is 15 metres but the 2nd minute you're at 3m EPE, it'll place a lot more weight on the time you're at the lower EPE. Thus, a more accurately averaged final position. Users who have experience with some of these more complex units will know that, given a good enough GPS accuracy (EPE) and averaged over a long enough time, it's quite possible to record a position that is within less than 1 metre (3 feet) of a known position (usually a benchmark of some kind). Pretty darn good for a hand-held unit.

As people have already pointed out, a point given as lat/lon corresponds to the same point in UTM - it's just a different way of entering an exact location. Personally, given a choice, I'll enter in UTM just because it's less numbers. There's really no other difference or advantage to either one except when plotting on a map or doing projections etc.

Me too - and I wanna go back! Snow is good!

Too bad! Anyone else selling one of these?

The Vista is good - some great features, and it's light and comfortable. It's only major drawback, from what I've found, is that the antenna isn't nearly as good as the quad-helix you'll find on most Magellans. I also have a Magellan SporTrak Map - another great unit, although without some of the features that the Vista has. Reception is much better in any sort of canopy, and it acquires WAAS corrections faster which gives you better accuracy faster. Maps are better than what Garmin has to offer, at least for Canada - for the USA, they're probably all really good. If only there was a unit like the Vista with a better antenna.... hey wait! There is! It's the Garmin GPSMap76S, which has all the features of the Vista and more. It's my next unit. Getting a GPS "just for caching" is reasonable, but eventually you may want to use it for more complex applications.

What the...?!?! I had a waypoint marked VERY close to that where Dagg was resting while I paddled over to another nearby island!!! Just so I could find him again on the return trip. That's a cool shot Dagg - it's also my desktop wallpaper at work now []

I've gotten a few emails already - haven't had a chance to reply yet but I will soon! Thanks guys!

quote:Originally posted by ZoomZoom:Sounds like Peregrine to me. I hear he likes to swim in the ocean alot. Nope, 'fraid not, ZoomZoom. I was out paddling with Dagg in the fog. That was kinda freaky though, not knowing which was is which! Pretty easy to get turned around - but we were prepared (as we usually are). :-D

I'm hoping a cacher from the Halifax area can help me with a little adventure. I'm looking for something that may or may not have 'disappeared' after your storm recently. Hopefully it's still there, but the area may not even be accessible yet as I understand that a clean-up is still in progress. I'll be happy to give you more details if you could email me (via the Geocaching.com emailer). Thanks!

quote:Originally posted by Insp Gadget: How come I never have this much fun????? Guess you don't have any 58-part multi-caches out there that take 6 FULL weeks to complete!