+RV Paces Posted March 20, 2004 Share Posted March 20, 2004 I am trying to get correct coordinants for my 1st hidden cache. I have been to the site 5 times and have 5 different numbers for the last 3 numbers both N and W do I put the "average" number on the worksheet. I can't seem to get a number that will be "right on the target" when I go try it out. I have put my box where I want it, but haven't listed it on the web yet as I can't seem to get the same number twice. I have a Magellan, MAP 330 I seem to get close to other listed sites, but setting up my own seems to be inconsistant. HELP! Link to comment
+geckoee Posted March 20, 2004 Share Posted March 20, 2004 (edited) From the guide Step 3 - Placing Your Cache ... Some GPS units have the ability to do averaging, but if yours can't, the best suggestion is to take a waypoint, walk away from the location, then return and take another waypoint. Do this around 7-10 times, then pick the best waypoint (I've done this with a Garmin eTrex on a cache) ... People will also tell you: * Just pick one. finders will tell you if it is to far off when they seek the cache. * waypoint averaging doesn't matter, just make sure you can see the sky. * Mark several waypoints, plot them on a map, and pick a point in the middle. * Average your coordinates over a 3 to 20 min interval. Personally I feel most comfortable averaging over a period of time with my eTrex yellow to a lap top. If I can't see the sky, then I average from 2 to 3 points and triangulate. With three points you can more clearly see your error, but is not necessary. This is probably also overkill, and only yields a slightly more accurate result, but I enjoy it, and that's what Geocahing is about right? Edited March 20, 2004 by geckoee Link to comment
+Wreck Diver Posted March 20, 2004 Share Posted March 20, 2004 How long are your GPS averages? I tend to leave my Meridian Color on the cache location for several minutes before marking it as a waypoint and subsequent searchers frequently mention that my listed coordinates were right on. Watching the latitude and longitude on the stationary GPS, the numbers seem to fluctuate quite a bit during the first two minutes, but it slows down and the numbers start to remain consistent after that. Average the numbers you currently have, then upload them and watch the logs. A longer average should help, but then again, entirely accurate coordinates diminish the search. Link to comment
+geckoee Posted March 20, 2004 Share Posted March 20, 2004 (edited) How long are my averages? The few times I have done it, not to place a cache, but just to see how the numbers would line up were: 3 hours under ideal satellites 5 minuets each at three locations, then repeat for 6 averages of 5 mins each. taking a bearing to the "ground-zero" location so all the data could be compared. 20 min strait average in non ideal conditions, verifying location with near by land markers. Edited March 20, 2004 by geckoee Link to comment
+RV Paces Posted March 20, 2004 Author Share Posted March 20, 2004 I didn't know about starting from a "landmark" location. Is this turning on the GPS at some steady point near the cache and then walking toward it? We walked from 3 different dirrections outside the spot and each time got different readings. I guess if we were reading someone elses, we would just scrounge around within 15 feet or so and we usually find it. I guess ours will work, we are just being cautions to get it right. thanks for all the advice. I think I will "log" it this weekend. Thanks. Sued Link to comment
+Wreck Diver Posted March 20, 2004 Share Posted March 20, 2004 How long are my averages? Sorry geckoee, we must have been posting at the same time. I was asking rvsued how long their GPS averages were. Link to comment
+geckoee Posted March 20, 2004 Share Posted March 20, 2004 I didn't know about starting from a "landmark" location. Is this turning on the GPS at some steady point near the cache and then walking toward it? ... by "verifying location with near by land markers." I meant taking bearings to places that you know the location of fairly accurately, like bridges, dams, road junctions, towers, maybe the peak of a rock. Ideally a bench mark of some sort. If you take these bearings relative to each other within 1 degree of accuracy you can place yourself pretty well. A little math: With two bearings you will get one intersection. If the bearings are taken at right angles to each other (the ideal condition) one degree of error “boxes you in” at 2cm of error per meter (really 1.7cm) So if the targets are 600m your error is 10m, which is comparable to a gps. For each point you add your accuracy will increase. Link to comment
+briansnat Posted March 20, 2004 Share Posted March 20, 2004 (edited) People will also tell you:* Just pick one. finders will tell you if it is to far off when they seek the cache. * waypoint averaging doesn't matter, just make sure you can see the sky. * Mark several waypoints, plot them on a map, and pick a point in the middle. * Average your coordinates over a 3 to 20 min interval. As the owner of 70+ caches, I can say with confidence that the second choice is the best. Averaging is a complete waste of time. If you have a bad sat alignment, you're just averaging bad data. If you return over a period of days, how do you know which day is the best? Just make sure you have a good view of the sky, take one reading and go with it. If your coordinates are bad, you will hear about it. But I'm willing to bet that you won't. Going through the logs for my caches, you'll see comments like "Brian's coordinates were dead on like usual". Little do they know that I took one reading with my eTrex and went with that. Two of my caches have garnered complaintes about the coordinates. One of them I averaged and the other I didn't. In both cases the searchers found the cache anyway, so the bad coordinates really weren't an issue. So take one reading and use the time you save to find or place more caches. Edited March 20, 2004 by briansnat Link to comment
+Mastifflover Posted March 20, 2004 Share Posted March 20, 2004 I don't have nearly as many hides as Briansnat but what I do is make sure I am getting good sat. reception then mark the waypoint. Walk away from the cache location and then see if takes me back to the same spot. If it does great I go with that number if not I mark a waypoint again and start over. Link to comment
+greengecko Posted March 20, 2004 Share Posted March 20, 2004 (edited) I try to stay in the area for 20-30 minutes taking up to 10-15 sets of coordinates during which I walk a short distance away in three different directions and return to the cache location. I throw out the highest and the lowest and average the remaining. This method has worked pretty good for me. Edited March 20, 2004 by greengecko Link to comment
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