SF and JB

I think you're right, I don't believe that the orthorectification process is perfect and honestly as long as everything on the map is spaced accurate distances in relation to each other it's still a safe tool to use even if the grid coordinates don't overlay on top of it perfectly. As mentioned previously I'm going to endeavor to discover just how much this error really is. The Google Earth error varies from place to place. I'm sure that for many traditional caches, Google Earth will get you close enough to find it. It might even be good enough, sometimes, to hide a cache. But it might not be, and then you run the risk of annoying a lot of people, including the cache reviewers. Remember, when you publish a geocache, you have to click those two little boxes declaring that you've read, understood, and followed the guidelines. Again, not trying to be mean, but it's a little presumptuous of you to tell a seasoned cacher with thousands of geocache finds and hundreds of hides that his coordinates are wrong based on Google Earth and a compass. It's neat that you're doing it this way, but Google Earth's inaccuracy is well known and much discussed in the caching community. A Garmin Map 60CX calculating coordinates on the spot with signals from 10 satellites vs. Google Earth and a compass in a region with a variable magnetic declination? I'll place my bets on the GPS. When I said safe to use I should have specified that I meant generally safe for personal navigation, not for placing caches. For the most part I understand and accept the argument against placement with just the tools I use now. Still to satisfy my own curiosity I am still going to try to borrow a GPSr and do a confirmation of the cache and a wider confirmation of GE using recognizable landmarks, as like I said my methods have produced sub meter accuracy in the past and as well I'd like to get a better idea of the limits of the tools I use. There was perhaps a slight degree of presumptuousness to my log on the subject cache, but I think in the future I'll still mention discrepancies between GE and cache coords as I think it might help prevent confusion from people who find caches as I do or even just for regular cachers who like to use GE before they get on site (not sure if this is overly common or not actually, but whatever). I will also change my wording a bit as well, rather then calling the posted coords off, I'll just mention that there's a discrepancy between the two, as that really is what is more likely to be the case.

I think you're right, I don't believe that the orthorectification process is perfect and honestly as long as everything on the map is spaced accurate distances in relation to each other it's still a safe tool to use even if the grid coordinates don't overlay on top of it perfectly. As mentioned previously I'm going to endeavor to discover just how much this error really is.

Interesting. You claim the cache is 45 feet off, but only 1 other person out of 183 finds mentions anything about the coords being off, and that person found it shortly after the cache owner posted new coords, so he may have been using the old ones. So why should I believe your map and ignore the 181 GPSes? Good question! I've had quite a bit of success in the short time I've been Geo Caching with my methods and have found caches where where Google Earth says they are and where they actually are is down to at least sub meter accuracy. This one didn't correspond to where Google Earth said it was, so that leads me to believe that there's either a geo referencing/orthorectification problem with Google Earth in the vicinity of this cache or the coordinates are actually off. The cache is a pretty easy one to find even with the coords being a little off, so I can see why people may not be inclined to mention or really even notice. I'm going to try to borrow a GPSr at some point and see what kind of results I get from a long period of time left in averaging mode on a nice clear day. I'd also like to make it clear that I get that the burden of proof is definitely on me with respect to this claim.

I guess this points out some orthorectification/geo referencing problems with Google Earth. It'd be interesting to do a bit of an audit of Google Earth by finding really easily visible locations with clear views of the sky with no buildings for double readings to interfere with signal accuracy and operate a GPSr in averaging mode at those locations and then compare with where Google Earth says they should be.

That sounds awesome, I'll check out the forum, if I ever get really serious about placing a cache, maybe I'll take you up on that offer to borrow the GPSr. I was actually going to go to the workshop on Thursday, but I had class.

I do.... here's one example: I did not realize you found the innacuracy of the coordinates of this cache to be due to GPS and not perhaps your methods. Thanks Toz! In my defense, I was shooting bearings from a point that was only ~25 meters from the posted coordinates and the actual geo cache, so I think my methods were quite accurate. I believe the problem may be with Google Earth and how it's aerial and/or satellite imagery is geo referenced, in the end it'll probably require me to go back to the cache with a GPSr with an averaging function to determine what the actual problem is, Google Earth or the posted coordinates, which I might try at some point in the future. In the end I suppose I may have been a little quick to assume that my coordinates were the correct ones. Perhaps next time I post a correction I'll endeavor to be clearer by stating something like "Google Earth says that the cache should be here"

"Letterbox hybrids are a mixture of letterbox and geocache. They should contain a signature stamp that stays with the box, and they must conform to the guidelines for geocaches and therefore must contain a logbook and involve GPS use as an integral part of the hunt. A letterbox hybrid cannot be designed to be found using only clues." http://www.geocaching.com/about/guidelines.aspx#letterbox I'm not trying to be mean, but I think you should stop looking for ways to circumvent the guidelines and wait until you have a GPS before you start hiding caches. Or take up actual letterboxing. So I guess that one kind of breaks the rules then? There wasn't a stamp or anything in it, it was just a geocache, the only difference was that the posted coordinates were intentionally off, but close to the cache.

Do you have a link to it? Just to satisfy my own curiosity is all.

That sounds like a good work around, thanks! I do think its possible to accurately place caches in some areas with just map and Google Earth. That is unless there are problems with Google Earth's geo referencing. I'll add a caveat to that, which is I understand that rules are rules and are there for what I imagine are pretty good reasons.

Also, what are peoples' thoughts on letterboxes, it'd probably be alright to place general coordinates that are near a letterbox with just a compass and GPS, right? Here's an example of what I'm envisioning: http://www.geocaching.com/seek/cache_detai...4b-fa4f5e5dbe3f

That sounds like a good work around, thanks! I do think its possible to accurately place caches in some areas with just map and Google Earth. That is unless there are problems with Google Earth's geo referencing.

I should add a link to the specific cache I'm talking about: http://www.geocaching.com/seek/cache_detai...93-7509bb676c51 My log entry was from today and is below: "N 45° 24.446 W 075° 40.333 Found it after some searching, I only used map and compass and shot a bearing from the N pointing corner of the tennis court. The cache coordinates are about 16m NW of the cache itself, I shot a bearing from the same corner of the tennis court before leaving and used it and google earth to determine approximately where the cache is and have posted those coordinates with this post. The cache was in pretty plain view as well, but I covered it up a bit more, TNLNSL. TFTC!" Someone also alluded to problems with Google Earth not being properly geo referenced, does anyone have examples of this? I know that imagery age can certainly be a problem, but I haven't been in a situation yet where I've felt the geo referencing was actually off.

I've been geocaching for less then a month and have found quite a few of them using just maps, Google Earth and a compass (I don't own a GPSr and am not planning to buy one) and today I came across one that was about 16 meters off of its posted coordinates. I determined this using the Google Earth ruler tool and a bearing shot from a landmark only 25 meters from the cache with my compass while at GZ and it got me thinking that I could definitely place caches to within ~1 meter accuracy with just Google Earth and a compass, provided there were some landmarks visible from Google Earth near the cache site. I'm hoping I could peoples input on this method!

Thanks to both of you, figured it out. It'd be neat if there was some sort of ranking system, with like goals and things, ie. find so many and get this icon or find so many of this terrain and/or difficulty and you get this icon. I suppose the general count provided kind of does that on its own. Anyway, thanks again!

I was wondering what the function is of the large emoticon on the "Your Profile" page of the website located on the right side of the page in the box labeled Hello (profile name)!. So far I've found 14 caches and I only have a basic membership so I imagine it won't change from the gray neutral emoticon in the near future, but I'm just curious if it changes with the amount of caches you find or with what kind of membership you choose to purchase or not purchase. Clarification would be greatly appreciated, thanks!

Those are cool examples, I'll look them up on wiki when I get a chance! I'll look for similar topics on the forum as well. I've got nothing against GPS users, for me though, limiting myself this way adds a neat dimension to the hobby.

Hey, I went geocaching with some people at work awhile ago and we all used GPS. I don't own my own GPS, but I do have a decent Sunto Compass with a folding mirror that I've been using this weekend along with a topographic map. I've also been using Google Earth to determine the bearing and distance from various landmarks to the caches I've sought out. I'd like to know if anyone else has tried this and what their observations are. So far I'm 3 for 5 just using compass, one thing I've learned is that you don't want to use landmarks that are more than ~400m from your cache as too much error seems to get introduced if you exceed this range. Any other input would be awesome! Thanks!