DaveA

To believe that a single reading is a good thing we pretty much have to believe that our first coord is the best and most reliable reading and subsequent ones are worse. I can't think of reason to believe this would be true except by chance. Quite true. We can't know. So by averaging we might end up with better coords and we might end up with worse coords. What then, is the point of returning to the location 3 times and averaging the coords? With SA we could know that with enough coords to average (which most units did automatically when not moving) we would eventually correct for the random errors and our coords would get better. The averaging at that time was done once per second and the rule of thumb was to let the unit average for 5 minutes which resulted in 300 coords to average. The averaging being done today is usually done, at best, 3 times. So 3 coords to average and for non random errors at that. Even if the errors were random, which they aren't, with only 3 datasets to average the effort would still be pointless. We might be getting more close coords than more further out coords. We might be getting errors that self correct, we might be getting errors that are amplifying the error. How do we know? We don't. Therefore the extra effort expended is pointless.

OK, let's assume that. Hey, no fair! You said you were going to assume the errors were non random The error from multipath is not random, it is pseudo random. You have to understand that mathetmatically speaking, random has a meaning. Only errors that are mathematically random can be reliably corrected for with averaging and even then it requires many datasets, not 2 or 3. Perhaps I should use the term mathematically random to hopefully reduce confusion on this subject. Ionospheric and multipath errors are non mathematically random, SA errors are. We no longer deal with SA therefore we no longer deal with mathematically random errors therefore averaging is of no help except occasionally, by pure chance/luck.

The errors are not random. True randomness and pseudo randomness are not the same. Averaging only corrects for true randomness. The idea behind true randomness is that over a long enough period of time the errors will become fairly uniform. Imagine a dot with a circle around it. That circle represents a diameter of 60ft, 30 feet to every angle from the dot in the center. This is the area in which all of our collected coords will occur. In a true random scenario like when SA was on by averaging over time, the coords, if plotted on our imaginary circle would be all over it in a reasonably uniform pattern. Averaging these coords would result in many of the errors canceling each other out thus improving accuracy. In a pseudo random scenario like multipath the errors may, coincidentally, have the same effect as random errors where they will cancel each other out, but if this occurs it was by chance. We can't know if it occurs. Each reading may affect the coords in an eastern direction (potentially degrading accuracy), or perhaps one time in an eastern direction and the next in a northern direction, but never in our readings is there a counter error to the west and south. So while averaging might improve accuracy in any particular case, it is by coincidence and it is just as likely to degrade the accuracy if the first coord was closer to the mark than the subsequent ones which get averaged in. I can understand that it appears multipath and ionospheric errors are random, but they are not really random, they are pseudo random. This whole idea of averaging was born in the days of SA when the primary errors were genuinely random and has carried over to today (I think) because old ideas die hard and it is counter intuitive to believe 5 coords averaged out wouldn't be better than just one. While it may be counter intuitive, it is true. To believe averaging is a good thing we pretty much have to believe that our first coord is the worst and subsequent coords will be better. I can't think of any reason to believe this would be true except by chance.

As a very general rule most any newer GPSr will do better under such conditions than most any older unit and the etrex is an older unit. However, heavy tree cover can pose challenges for the even the best of the recreational GPSrs.

Wouldn't banning his account just be a symbolic gesture? Anyone can see the caches and TB locations. It is unfortunate what happened, but I don't see that even banning this person's account is going to offer any protection against this sort of thing.

Given you believe that much in the value of WAAS, you need to weigh-in against the group that feels WAAS is of little to no value. Click here for an example. Usually the people who feel taking multiple coordinates is of little or no value are the same people who think that about WAAS too. You seem to be an exception. Next time the frequent discussion of the merit of WAAS comes up you can join those of us who think it's helpful. That way you, I and fizzymagic can be on the same side. ok

I agree with you that we can get different accuracy at different times. I am unclear on what FizzyMagic said that you are agreeing with since you are rejecting the averaging of non random errors (which it appears he is arguing for) in favor of selecting the waypoint with the least deviation.

This is why I hate these kinds of conversations. I didn't say "facing in another direction!" I said "approaching the site from a different direction." If you really want to have a discussion about this, it is key that you actually read what others write with the intent of understanding it. In order to avoid derisive comments, I will stop at that. I will not be misquoted. This discussion is over. Your temper tantrums aren't going to make you more correct. I addressed your points. If you are unable to deal with them then you are correct, the discussion, with you, is over. If you prefer change what I said from "facing direction" to "direction of approach" and it makes no difference. Net result is the same. Multipath and ionosphere errors are not random and therefore they cannot be corrected for with averaging. Averaging non random errors is pointless. Any mathematicians in the house?

I am sorry, but this is incorrect. Yes, multipath errors are geometry dependent, but not because facing a different direction will result in different satellites being used (It generally won't, the birds are high enough that they don't care which way you are facing). Geometry dependent means that multipath signal is coming from a particular direction. Hence, the error will not be random, but consistent. Multiple readings cannot correct for a consistent, non random error. for more information on multipathing please see this Partially true. However ionospheric errors are corrected for via WAAS. If you are getting a WAAS lock you don't need to concern yourself with it. It is true (as I understand it) that this type of error is reduced at night. Yes, I am happy that instead of giving dogmatic, non backed up derisive comments you are presenting information which can be discussed. Thank you for that.

well, consider this scenario before you go appreciating the efforts too much : joe cacher goes and places his cache and his GPSr gives him a set of coords. His EPE (estimated position error) according to his GPSr is 10ft. Joe then returns to the site the next day and takes coords again. The new coords are 50ft away from the first coords and his EPE is 75ft. Which set of coords do you think would be the more accurate? If you answer the way I do that the coords with the 10ft EPE are statistically more likely to be the more accurate of the two coordinates then here is the million dollar question: How does averaging these two coordinates improve the accuracy of the coords Joe Cacher lists on his cache page? Shouldn't he have just moved around a bit, faced different angles, tilted his GPSr and done whatever he could to get the lowest EPE possible and use those coords? Which approach would have yielded the more accurate coords?

This isn't the kind of averaging we are talking about when we say it takes too much time to be worthwhile for many. We are talking about returning to the same place on different days and different times of day from different directions and averaging those coords. The type of averaging you are talking about uses proprietary algorithms that I know nothing about and probably also includes some limited multipath detection as well to toss out some coords and prefer others in order to display the best possible position fix. The type of averaging you are talking about may very well produce a more accurate set of coordinates. To know whether it does or not would require understanding proprietary info about each manufacture's units as well as an ability to comprehend them. It seems Magellans do this by default when stationary and Garmins do it optionally if you tell them to. Don't know whether or not this is at all significant.

No point. We've been around and around this topic too many times and I am sick of it. I am stunned because, despite consistently good evidence (and even gasp data) to the contrary, people keep bringing up the same flawed arguments (e.g. "averaging can make it worse," "there is no random error," "the searcher's GPS has a big error anyway, so it doesn't matter," etc.) So in other words you won't address the argument I made? I don't believe I have ever weighed in on this discussion before so I am not one of those who discounts evidence. I am interested in your evidence. Please present it. I presented what I believe to be true based upon the knowledge I presently have. If you have additional or contradictory knowledge I would appreciate learning of it. Here is what I claimed based upon my present knowledge. I will make a claim, and then support it with my argument. I will label each part to make it easy for you to identify the part that is incorrect and explain why it is incorrect. CLAIM: Averaging does not improve positional accuracy. SUPPORT: Averaging can improve accuracy if the errors are random. SA produced random errors which averaging could minimize. SA is no longer present. Multipath and upper atmosphere conditions do not produce random errors therefore averaging cannot correct for them. Please show where I am going wrong.

Ok, I am even more stunned now. It's even worse than I thought. Wow. Perhaps you could articulate the reasons for your being stunned. Y'know, to further a discussion.

OK, I am officially stunned speechless. And to think that some of those people have been caching for more than a couple of years! OK, let's not get into a pointless debate, let's just summarize the facts in this controversy. Why would one assume averaging coordinates would improve accuracy? The idea behind this belief is that the errors in position are random. If it is true that the positional errors are random then averaging can improve accuracy. The idea is that coord 1 is dead on, coord 2 is off by 15 feet to the north, coord 3 is off to the south etc. Using enough random errors what happens is the errors cancel themselves out. In other words if the errors are random we can expect one coord to be off to the north and another off to the south. These two errors would bring the result more to the middle thus improving accuracy. Why would one assume averaging coords would not improve accuracy? The idea behind this belief is that the errors are not random. If they are not random then all coords are likely to be off in the same general direction. Averaging multiple sets of coords that are off in the same direction won't produce a better result and could produce a worse result (assuming the additional coords are further off than the first). The question then is "Are the positional errors random?" The answer is 'probably not'. Back in the days of selective availability the US government intentionally sent coords that were innaccurate to reduce the precision of GPSrs. These errors were random. SA has been off for a long time now. Currently the errors we deal with are not random, but are caused by multipath (signal bouncing off objects) and satellite error among other potential factors. Because the errors are not random, it would seem averaging is at best, pointless. However, that isn't the end of the story. If we approach the cache site at different times and from different locations we might be able to improve accuracy via averaging. Why is this? Well satellite error ends up getting corrected. Multipathing may be reduced when not approaching thru the heavy tree cover or large rock wall. The question you have to ask yourself is getting slightly better coords worth visiting the site multiple times at different times of day on different days and from multiple directions? Wouldn't it be easier to simply look at the GPS indicated EPE and do what you can while on site to get it as low as possible and then save the coords? It has come to my understanding that Magellan units have some sort of goofy auto averaging that requires one to sit still for a few seconds before the coords 'catch up' with the actual location, but this should not be confused with averaging. GPS ''settling' is the term used to describe the need to sit still for a few seconds to get the best coords under such circumstances. I dont understand the algorithms the GPS manufactures are using so I can't explain why this is or isn't necessary for any given unit. Anyway, that's all I have to say on this subject.

people that can find a cache just comparing lat/lon numbers are waaaaay smarter than me. I require the arrow to point the way. Numbers, bleh, pictures and graphics are the way to go. Your 9 year old uses the numbers you say? Get that one into a school for the gifted.

dunno if any have what you want. I think the 'gold standard' display screen for caching is the compass screen. On my Meridian Color this is not an electronic compass, but it doesn't need to be. what gets displayed here is a icon indicating the cache and a compass arrow. One just walks toward the cache icon. Above the compass are 2 customizable fields. I have them set to show distance to destination and EPE or estimated position error. I am unclear as to why you would want the lat/lon coords displayed on this screen.

no idea what they mean. I spent about 10 minutes following the link IV Warrior provided to no avail. Are you sure you have them correct? TFTF and FTFT? TFTC=thanks for the cache, no idea what TFTF means. Likewise FTF=first to find, no idea what the T on the end means.

the cable doesn't come with software. You don't need to buy any software if you simply want to load waypoints onto the unit, you can use free software like EASYGPS or GSAK for that. GSAK in particular is custom made for geocaching and does pretty much anything you could want it to. EASYGPS is less featured, but it is extremely simple to use and tosses waypoints around like nobody's business.

If you log a note there is no impact that I can think of, but if you log a DNF this shows up, without explanation, in offline programs like GSAK and others. As has been mentioned some folks won't seek a cache if the last log was a DNF because they figure it might be gone and so they will pass on it. With that in mind it is my opinion that your circumstances warrant a log rather than a DNF. You didn't search for the cache and if you didn't look then of course you didn't find. DNFs, in my opinion, are for when you look and don't find. You didn't look.

it is a bit neater if you are a premium member with access to pocket queries, but the bottom line is there is no way to see caches along a route in one step. What you would need to do is use map software to get the coords to various places along a highway. Then do a search for caches within 1, 2, 5 whatever miles from that point. You would need to repeat this all along your route as often as you felt like pulling over. Alternately you can download a bunch of caches within say 100 miles of a point on the highway and import them into your map software (assuming you have vendor specific map software) and delete all waypoints that are too far off the highway for your needs and then upload those remaining to your GPSr. Since you don't have much time I would suggest downloading as many caches as your GPSr will hold and just let the unit show you what is close to your present position. Again, premium membership makes this a bit easier as you can just download 500 waypoints meeting whatever criteria you like within whatever radius you want and you get them all in one file, but that is something to consider for another time. Have fun.

The logs indicate that it is buried and on private property so it is entirely possible the placer has permission for it. I think the cache page could be more indicative of this fact if it is indeed a fact, that is for sure.

getting on, but too slow to be usable. editted to add: strike that, getting errors now.

Indeed, see this thread for some ways to incorporate google maps with this site as well as GSAK.

Never ask permission unless there is a posted policy requiring it. If there is a posted policy requiring it, try to find some other area to place a cache. I trust you have learned your lesson. You behaved in an honorable way. You did the right thing. You saw first hand how your government works. Now go do the practical thing. Be thankful that government at all levels is mostly incompetent otherwise we would be really screwed.

It must be scary where you live, I have never felt afraid of the people when I go caching. Then again I don't do caches in Milwaukee's inner city, I stay more rural. I also generally don't do caches where there are lots of people. I am fairly choosy that way.