When using 2 GPSrs to mark a location (with good reception), tests have shown that sometimes the coordinates are remarkably close and sometimes they will vary more that double the "accuracy" shown by the perfectly functioning GPSrs. This is due to the random nature of which direction the GPSr is off the actual coordinates. If the 2 GPSrs happen to have an error in the same direction, then the coordinates are very close. If the 2 GPSrs happen to error in opposite directions, the coordinates then appear much further apart. Because of radial nature of the error (which requires a geometric and probability density explanation), most of the time the 2 GPSrs show a difference that is not perfect, but not the extreme. This unfortunately gives the user a false sense of consistancy, so when the accuracy differences are in different directions, they think something is wrong (bad coordinates) when actually nothing has changed. For example if 2 GPSrs mark a waypoint with 4 meters accuracy, aprox 75% of the time the marks could be within 6 meters, often much better. But occasionally the marks will be 8 meters apart, with nothing changing exept the luck of the draw. In reality the effect is even worse as GPSrs can be optimistic about the "accuracy" they display, plus the averaging that some GPSrs use will penalize the impatient user! The punch line is that if a cache is logged with an accuracy of 4 meters, complaining about finding the cache less that 10-15 meters away only shows you don't understand the capabilities of a handheld GPSr. If you go to find this cache, you are asked to:
Feel free to come back to this cache on as many different days as you like to see how a single GPSr can vary on different days! Sorry but I am no long adding new points to the graphs. Thanks for participating in this demonstration! (Please be nice in the comments that you post. People hide caches for fun, so don't take away their fun, we need people to hide caches! Sorry, but to protect the delicate feelings of some of the people who helped set up this cache, complainy logs will be deleted without notice, thanks!) |
11/15/2006 by Kabuthunk
Decided to tackle some more caches in this neck of the woods. Ever since I did those other caches nearby this one (I think it started with a Mayor of Winnipeg close to this), I've been wanting to take on this particular one, mainly because the name is a tad unusual. Too bad it's not updated with waypoints any more. Well... I forgot to log what my coords for the cache were anyway .
A little after I arrived at the cache location, I started to get really worried that something had happened to it. The reason for this worry is that there was a mangled-looking ziplock bag on the ground in the area. However, I didn't see any paper, or swag, or anything else, so I continued on. After a bit of poking around, I gave in and looked at the hint. Well... I was looking way the hell in the wrong direction . Didn't take me long after that to spot about the only place it could be hiding. And indeed, one arm-reach later, I was correct .
Was bitterly cold out though, so I couldn't write much in the logbook. Ah well... tis the way with winter (or close thereto) caches. Nice spot though .
Took: Nothing
Left: Chainmail ball
Hints (Back)
Bring a stool if you are under 5'10".