Horizontal Accuracy and Waypoints

[Guest fryed]

I don't know if this has ever been brought up before but I have a question. Would it make sense to include a horizontal accuracy value along with the coordinates for each cache as they are entered into the system? That might allow us to know how close to the stash we are when our recievers say we are right on top of them. I know that if I go out on one day and get a set of coordinates I may get a slightly different set the next day. In the words of Joel from MST3K, "What do you think, sirs?"

[Guest Richard Amirault]

Well, A hunter has to have *some* talent .... I don't really expect (or need) to use my GPS to get me to within 12 inches of the cache. When it says I'm within 10 or 12 feet *that's* close enough and I stop looking at the GPS and start looking for the cache.

[Guest jeremy]

Not all GPS units have an "accuracy" value. That may only be an eTrex thing (or Garmin thing, etc.) So unless it's global to all GPS receivers I keep it off the required list.

 

30 meter accuracy means that you are in a circle 60 meters in diameter. You could be on top of the coordinates for all you know. I

 

Jeremy

[Guest trilobites]

The horizontal error is only an estimate of the error and says little about the accurracy and precision of the point. Different units will have different "errors" at different times. Your better off marking the cache location 3-5 times and averaging those points or more as suggested on the geocaching "hints' page.

One way to really see how well your unit is doing is to find a benchmark and mark the location many times. I've done this at a USGS benchmark in front of my office (the guys next door set it) here in Rolla with an etrex summit and a $10,000 DOD Rockwell unit. As of yesterday, the etrex summit is nearly as close as the Rockwell unit, except for the Rockwell unit has a much better antenna. After I get a bunch of readings, I'll post the results. By doing the above you get the an estimate of the accuracy and precision of the unit. Its also a good way to check the unit before heading out in the "field".

A faster way is just to mark a location at your house (mailbox etc.) over a month of so and plot you results, its interesting to see how readings drift at various times of the days, etc.

[Guest Team Griswold]

I think that an altitude cut off the GPS would be a good data item to include in the post for a geocache. This would let someone know if the searcher needs to switchback down lower or higher to find the site. Also letting newer geocachers know how much vertical climbing is required. Anyway, this discussion just got me thinking...