jfitzpat

Actually, I'd have to disagree. Kerry, and others, have put up some pretty good studies that show that averaging actually can generate less accurate results in many circumstances. My daughters were going to place our first cache near Switzer Falls. The path follows a narrow granite ravine. The spot they liked would be tough going for any receiver, not because of cover, but because of line of sight to the sky. We climbed up either side of the ravine and got good readings. We then measured bearings to the proposed sight. Our thought had been to triangulate the position, then eyeball it for accuracy on http://www.lostoutdoors.com But then we decided that it was a bad fit for the trail (bascially, the climbing and triangulation would make a great family cache pretty stiff). But the method itself works well (get accurate readings around the cache, use bearing (and possibly distance if you can pace it off) to correct, and eyeball it on an aerial map to confirm. It sounds like a lot of work, but it should nail down true coordinates more reliably than just taking a bunch of readings at the site and averaging them. -jjf P.S. We have, so far, had really bad placement luck. Our next plan was to go ahead and place a 5/5 in April, we got rained out on our first trip, and snowed out on our second! We left some slings on both retreats, but no cache...

Actually, I'd have to disagree. Kerry, and others, have put up some pretty good studies that show that averaging actually can generate less accurate results in many circumstances. My daughters were going to place our first cache near Switzer Falls. The path follows a narrow granite ravine. The spot they liked would be tough going for any receiver, not because of cover, but because of line of sight to the sky. We climbed up either side of the ravine and got good readings. We then measured bearings to the proposed sight. Our thought had been to triangulate the position, then eyeball it for accuracy on http://www.lostoutdoors.com But then we decided that it was a bad fit for the trail (bascially, the climbing and triangulation would make a great family cache pretty stiff). But the method itself works well (get accurate readings around the cache, use bearing (and possibly distance if you can pace it off) to correct, and eyeball it on an aerial map to confirm. It sounds like a lot of work, but it should nail down true coordinates more reliably than just taking a bunch of readings at the site and averaging them. -jjf P.S. We have, so far, had really bad placement luck. Our next plan was to go ahead and place a 5/5 in April, we got rained out on our first trip, and snowed out on our second! We left some slings on both retreats, but no cache...

You could probably do it with a simple circuit and most GPSr's now. Put the GPSr in NMEA mode, 4800 baud. Use a little modulator circuit (you could use a high tech modem chip, or an ancient TarBell ('Kansas City Cassette' to us foggies ) circuit. Then, record the NMEA stream on audio. I don't know about the latest recorders, but our older Sony would allow me to kludge external audio on "right" and still keep the built in mic recording on "left". When you play back the tape, demodulate the audio, and feed the decoded NMEA stream back into a PC program, etc. You could probably fit the circuit in a connector body and steal juice right off the data port. -jjf

You could probably do it with a simple circuit and most GPSr's now. Put the GPSr in NMEA mode, 4800 baud. Use a little modulator circuit (you could use a high tech modem chip, or an ancient TarBell ('Kansas City Cassette' to us foggies ) circuit. Then, record the NMEA stream on audio. I don't know about the latest recorders, but our older Sony would allow me to kludge external audio on "right" and still keep the built in mic recording on "left". When you play back the tape, demodulate the audio, and feed the decoded NMEA stream back into a PC program, etc. You could probably fit the circuit in a connector body and steal juice right off the data port. -jjf

quote:Originally posted by Night Tracker: My brother and I would cache c-rations then later MREs in the national forest in far in places so that when we ventured in during the late hunting season we would map out the coords to the hiden cache. It was fun to relocate these after a snow fall. We would each share the written coords to our hiding spots. Now we can fall back on this if we feel like being real men, but the GPSr is alot of fun too.. One nice thing about D rations (the survival cousin of the old C and K), you'd never snack on them and leave yourself in a pinch in a real emergency... MREs aren't that bad, but I'd still have to be awfully desperate to go actively search for one! -jjf

quote:Originally posted by Night Tracker: My brother and I would cache c-rations then later MREs in the national forest in far in places so that when we ventured in during the late hunting season we would map out the coords to the hiden cache. It was fun to relocate these after a snow fall. We would each share the written coords to our hiding spots. Now we can fall back on this if we feel like being real men, but the GPSr is alot of fun too.. One nice thing about D rations (the survival cousin of the old C and K), you'd never snack on them and leave yourself in a pinch in a real emergency... MREs aren't that bad, but I'd still have to be awfully desperate to go actively search for one! -jjf

quote:Originally posted by xeman: To be a little more Yet, with topo, the MeriGold can show your position 1/2 way up the mountain you're climbing?!?! Keep in mind that the topos are scaled down versions of 1:100000 maps. So, an elevation profile generated from them is going to be really crude. For example, the profile from Humber Park to Lily Rock looks like a steady slope, with 2100' of elevation gain. In fact, you gain 1200' over about .4 mile, then the rest in a couple hundred feet (it is a granite cliff). An elevation profile of where you have been will be much more accurate. Good Luck, -jjf

quote:Originally posted by Atilla the Pun: The Vista has a patch antenna and looses signals where my Map 330x (same antenna as the Platinum) still has a 3d lock. The Platinum has a 3d compass, you don't have to hold it flat for a good directional fix with or without sattelites. The Vista must be held flat, both for reception and for the compass to work. I'd get the the Platinum if that's the two GPS's you're trying to decide between. Oh, no SD card on the Vista, up to 128 MB external memory (SD card) on the Plat. AtP I use a Vista, for reasons I've stated many times, but if I were to buy a Merdian, I would probably buy the Gold. The 3D compass on the Platinum may seem cool, but it is pretty inaccurate. IE, it works at many attitudes, but it is not terribly precise at any of them. I thought that it was just one unit, but it is actually the sensor used. And the barometer is not really a replacement for a barometric altimeter. Most users don't need one, but if you do - you'll still be lugging one along side your platinum. I'm not saying that the Platinum is a bad unit, just that I would go for the better battery life and slightly lighter weight of the Gold (actually, I don't know if the Gold is lighter or not - but it does go longer on a set of batteries). -jjf

Both Garmin and Magellan maps are pretty mediocre. A 1:100000 topo is no replacement for a 7.5 min topo. And, no map is easy to use viewed through a tiny window. Streetwise, both are OK, but again, not really a replacement for a good Atlas on cross country trips. So, your first criteria isn't really well met by either. Ease of use is pretty much a draw. I personally carry a Garmin, but think Magellan front panels are easier to operate. I seen Magellan owners claim that they think the Garmins are easier. I've never had trouble figuring out either. If you are thinking about car reception and maps, then you might really want to consider other units. An eTrex model is great for hiking, but the screen is too small to gawk at while driving. The Meridian's have larger screens (but lower resolution), and can be operated with one finger - a plus in the car. But... none of the handhelds get very good reception in my SUV, so if driving usage is important to you, you might want to look at units with external ant. connections (which the Vista and Meridian units do not have). Good Luck, -jjf

No, you do not need a GPS receiver. However, even if you have excellent orienteering skills, many caches may be more difficult than you think. My daughters use 7.5 minute topos and a Silva Ranger compass. But, their success rate would be much lower if I didn't let them augment with NAPP images from http://www.lostoutdoors.com Remember, a 30' cliff can go unnoted on a 7.5 min topo - but top or bottom of that cliff, like which side of a river or stream, can make a huge difference when you are looking for a ammo can sized container. The sport would probably be too course if GPSr's weren't routinely used for hiding. -jjf

No, you do not need a GPS receiver. However, even if you have excellent orienteering skills, many caches may be more difficult than you think. My daughters use 7.5 minute topos and a Silva Ranger compass. But, their success rate would be much lower if I didn't let them augment with NAPP images from http://www.lostoutdoors.com Remember, a 30' cliff can go unnoted on a 7.5 min topo - but top or bottom of that cliff, like which side of a river or stream, can make a huge difference when you are looking for a ammo can sized container. The sport would probably be too course if GPSr's weren't routinely used for hiding. -jjf

quote:Originally posted by MrGigabyte: [snip] This is commonly done in the geomatics world by using a Helmert's Similarity Transformation. Helmerts is built in to most Survey grade GPS data collectors and also most handheld calculators that have Surveying modules (i.e (HP/TDS). Off the top of my head, I was only familiar with Helmert's 'gravity' (Helmert's 2nd Condensation, etc.). I walked over to the library (its just a couple blocks from our downtown office) and did a search. When I came across: "Martinec, Z.,The Static, Potential Free Love Numbers for a Homogeneous Earth Model Bounded by an Irregular Surface, - V.17, pp.186-200, 1992." I decided that, like Markwell, my brain is full... -jjf

quote:Originally posted by Anders: It seems that some people are packing for a long move. Like western soldiers, always burdened by all the paraphernalia considered necessary to conduct warfare. I usually bring: GPS (for obvious reasons) Batteries (if I know that the GPS is low on fuel) Pen (since it often doesn't work, if there is one) Trade item (if I have any) Phone (to tell my wife that yes, I'll come home... sometime... when she calls) Anders But Anders, we don't all have wonder suits! Some of us need to carry water instead of being re-hydrated by our processed sweat! Likewise, no clothing I have can elliminate my need to haul a little toilet paper in a baggie. Something about hiking uphill on a rough trail really loosens things up - and none of my pants have, errr, processing facilities! And, of course, if I had X-ray vision like you super hero types, I could leave my LED headlamp at home as well... -jjf

quote:Originally posted by Anders: It seems that some people are packing for a long move. Like western soldiers, always burdened by all the paraphernalia considered necessary to conduct warfare. I usually bring: GPS (for obvious reasons) Batteries (if I know that the GPS is low on fuel) Pen (since it often doesn't work, if there is one) Trade item (if I have any) Phone (to tell my wife that yes, I'll come home... sometime... when she calls) Anders But Anders, we don't all have wonder suits! Some of us need to carry water instead of being re-hydrated by our processed sweat! Likewise, no clothing I have can elliminate my need to haul a little toilet paper in a baggie. Something about hiking uphill on a rough trail really loosens things up - and none of my pants have, errr, processing facilities! And, of course, if I had X-ray vision like you super hero types, I could leave my LED headlamp at home as well... -jjf

quote:Originally posted by orygun: So I can purchase either a Garmin etrex or a Magellan 315 for the same price. Brand new to GPS and Geocaching? Really need pros and cons of both units. Thanks I agree with a previous post, both are fine units. The eTrex is smaller, lighter, sturdier, and waterproof. It also gets about twice the battery life. But, many users report better reception with the ant. in the GPS315, especially under heavy tree cover. -jjf

I'd have to agree with Jeremy, the 315 and eTrex are the most reasonable choices. The eTrex is smaller, lighter, waterproof, and has about twice the battery life. The GPS 315 has a better ant. and is, I think, easier to operate - though the averaging drove me crazy (I haven't tried a 315 with new firmware). -jjf

quote:Originally posted by harrkev: This is strong competition to the eTrex line. It gives you almost the same memory as the Vista is approximately the same size. Backpackers are VERY concerned with size and weight. Now, Magellan has something to offer these people. I'm sure that was Magellan's intent, but it seems like they are playing more to their weaknesses than their strengths. The unit is still big and bulky by eTrex standards. But, the smaller screen seems a lot less usable than the Meridian's. From the unit I saw, it does not seem that Magellan increased the resolution (at least not significantly). And, the basemap seemed terrible. Theoretically, it should be on par with the eTrex base maps, but it certainly wasn't for SoCal. The one thing I didn't get to see is data rates. If the unit loads maps via RS-232 as slowly as a Meridian, I'd see that as a big problem. At least with the Meridians you can use an external writer for the SD memory. And, I'd have to agree with another poster, if you care about ounces, the Vista is more instrument for the weight. Certainly, being able to drop my old altimeter helped me justify dragging mine to the mountains. -jjf

quote:Originally posted by Warm Fuzzies - Fuzzy: All of this is untested, so it's possible a sign or other error creeped in somewhere, but I think it's right. Seems correct. All the old navigational and astronomy texts I have generally solve this as a spherical triangle. But, as long as you are confined to one zone, it seems that a linear solution on a UTM projection is about as accurate, and less computationally intensive. -jjf

I'd go for the Gold. Having played with both, I'd say the basemap is worth it. Also, keep in mind that the specifications for temperature range, impact, and etc. are for the unit itself, not 3rd party memory cards. I've seen a green lock up in the cold - well above its spec'ed minimum operating temperature. Only to come back to life when the no-name SD memory card was removed. (No, we weren't that smart, we just took it out to re-seat it.) -jjf

Despite intense brand loyalty, all three of units you mentioned would be fine for geocaching. Each has its own strengths and weaknesses. I'd suggest going to a store and playing with them. Then pick the unit that best suits your personal taste and specific needs. For example, if you backpack, cross country hike, or mountaineer, you might really like the eTrex line. Smallest, lightest, best temperature range, and geared towards one hand operation. Since I would carry an altimeter on some of my adventures anyway, the eTrex Vista helps 'earn' its ounces for me by including one. On the other hand, if you are more likely to use the unit in your car than on a "14", the Magellan might appeal to you. The screen is much lower resolution, but physically larger. The front panel button arrangement is also better suited to one finger operation. Both these aspects make the unit more practical to operate in a car. And so on... Again, they are all pretty nice units. Good Luck, -jjf

quote:Originally posted by Anders: A celebrity in the geocaching world, or elsewhere (too)? Anders Anders, I think that the fashion world counts too... -jjf P.S. Thought you might like these: http://www.iww.is/art/shs/pages/thumbs.html Still trying to talk my wife into the hiking and/or dog sled trip.

quote:Originally posted by Anders: A celebrity in the geocaching world, or elsewhere (too)? Anders Anders, I think that the fashion world counts too... -jjf P.S. Thought you might like these: http://www.iww.is/art/shs/pages/thumbs.html Still trying to talk my wife into the hiking and/or dog sled trip.

quote:Originally posted by peter: Sorry to pick one more nit in a thread where too many have been picked already, but it's actually the other way around. Perihelion (smallest earth-sun distance) occurs in early January and aphelion (greatest distance) occurs in July. Yes, this has been picked to death, but I am going to try one more time to spell out my points. I've done a really poor job so far, and just worked someone else into a frenzy. First, we start with the GeorgeAndMary model of seasons (which I do not contest, I just say is incomplete in terms of climate). For those that already know this, please forgive my spelling it out again. The idea is basically that the earth goes around the sun, tilted. For the most part (aside for a factor we can ignore), the tilt remains steady in relationship to the sun. This means part of the year one hemisphere is tilted towards the sun, the other part of the year the other hemisphere is tilted towards the sun. Now, we take light. The sun is so far away that it acts like a point source to us. That is, the light 'rays' (photons really) are parallel to one another from our perspective. Now, what GeorgeAndMary is saying is that the closer to perpendicular these straight lines strike the earth, the closer together they are. Perpendicular, the spacing matches the spacing of the lines. As the angle increases, the spacing between intersections increase. In other words, the same amount of photons are spread out over a greater area. You can demonstrate this to yourself with a couple of pieces of lined paper. This is true, and the principal force behind seasons. Stopping here, lets go waaaaay back to my original point. Take a baseball, draw an equator on it, and put a dot where Des Moines, Iowa would be. Now sit in an auditorium, with one lightbulb on at one end of the room and you and the ball at the other. Now, tilt the ball 23-24 degrees with respect to the light. The tilt itself looks very small, and the visual change imperceptible. But, that change plays a big part in Iowa cycling between 100 degree armpit heat and search for your car with a stick below 0 cold. If you go farther and work out the math, spacing of the photons against the angle of impact and the curvature of the earth, the change, as a percentage of the whole, is also surprisingly small. Smaller, in fact, than can account for the seasonal changes that most of us are familiar with. Which moves on to my next point. It is not just the angle, but the total transfer that counts. Light is a form of electromagnetic radiation, or EMR. Radio waves are another form of EMR. Most of us are familiar with AM radio waves acting one way (bouncing around) and FM radio waves acting another. Visible light has similar properties that must be accounted for, but, again, acts differently because the EMR is a different wavelength and AM or FM radio. In order to get our math to come out close, we have to account for the behavior of light with respect to things like the atmosphere and the surface material being struck. We all know that a black cotton t-shirt and a white cotton t-shirt will offer different comfort levels on a sunny summer day, the earth is the same. Likewise, we all know that sunlight can make a bright reflection, depending upon angle, off a lake, and that the atmosphere contains a lot of water. Last, we can come back to both my original point, and my most hotly contested point. It is true that our northern hemisphere winter comes when we are closest to the sun (about Jan 3rd? I'd have to look it up). But that does not mean that the distance is not relevant. Average climate is not identical in both hemispheres. We have the same seasons, but the intensity of the weather is effected, in part by the fact that our equivelent seasons occuring at different distances from the sun. Now, how does this relate to my original point? As GeorgeAndMary pointed out, our orbit is, in fact, elliptical, but if it were shrunk down to human size (say, a dinner plate), it would look pretty darn circular. But, that tiny deviation, like the modest bulge in the earth, have a very real impact on climate. But, as I kept trying to stress to GeorgeAndMary, even that is a wholly incomplete model. Many other factors play a part in the differences between hemispheres. For example, land mass is not evenly distributed. Water and Land have different thermal properties, which, in turn, has an impact on the air currents and weather above them... And so on. Last, this is just a side note to GeorgeAndMary, I think that the whole butterfly thing is crap. For that matter, I think that chaos modelling is a load of do-do. That said, I've had more than one mathmatician make similar comments about QED. -jjf

quote:Originally posted by DisQuoi: quote:Summer/Winter has nothing to do with distance from the sun, it has to do with the angle at which the sun hits the earth. Earth's axis being tilted and all. And that change IS big.There's a good discussion of this at the http://www.hao.ucar.edu/public/education/general/general.html. After reading it (and the post of jfitzpat), I would say that the seasons are tied only to the tilt of the earth's axis. However, the temperatures on the planet as a whole may vary slightly depending on the distance from the sun but that's not the same thing as "Seasons". That is to say, while winters in the northern hemishpere might me colder due to the aphelion occuring in January, it's also resulting in cooler summers in the southern hemisphere. I would agree, and you are stating it better than I. As I just indicated, I am not very good at explaining certain things, and the entire subject is pretty far from the original point I was trying to make (I lumped seasons and temperate zones together, because I meant to indicate global climate). -jjf

quote:Originally posted by georgeandmary:Summer/Winter has nothing to do with distance from the sun, it has to do with the angle at which the sun hits the earth. Earth's axis being tilted and all. And that change IS big. [snip] You do bring up a good point about length of the day and duration of impact but what determines the length of the day? That's right the angle of the earths tilt (as I said), and your latitude... [snip] Let's back up a step. You started by overstretching my my original statement. I gave several, issues (season, temperate, zone) and one factor (distance), and indicated that there are others. I was trying to make a general point. If you are indicating that I disagree that seasons are principally driven by the 23.5 degree (approx) tilt between the earth's axis of rotation and the plane of the ecliptic, you are incorrect. I *am* saying that *climate* is impacted by effects other than basic tilt. For example, weather severity is effected by everything from solar storms to axial procession. I am *also* saying that distance to the sun, like anything else the effects energy transfer has *some* effect on climate. If you disagree, move to Neptune... Regarding my 'length of day' statement, I was trying to convey that the issue is total energy transferred, not nec. the angle it is delivered at. The distinction is important when examining the poles. Unless you factor in things like denser air over cold ice, lower absorbtion rate of light colored ice packs, etc., the poles defy simple math (they actually still defy current models, but that is another story). I picked a simple explanation to make the point, because 1, this is a forum and not everyone has the same background in certain subjects and 2, I don't explain these types of physics well. My explanation and offer were not a flaunt, but face value. I can get you great information on a fairly complex subject, and this isn't my area. The offer was made with the idea that you were actually interested in the physics of the situation. However, in re-reading the posts, I suspect that your motives are a little different. I'm not sure how much of the geom/trig you quoted you know, and how much you quoted from another source, but clearly I am the last person you would want to get nitpicking from. -jjf