GPS Accuracy revisted

[Guest Ron Streeter]

I know it's been discussed before (maybe to death) but as there are always new cachers and sometimes new views by oldtimers, I offer this post.

 

I got this nice note from Ray and thought I would show my reply here as I think it applies to all our caching efforts. I welcome other people's opinions on the subject.

 

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Hi Ron,

 

I see you made it to the BBQ Walnut cache. You seem to be one of the

GeoCache experts. How do you like your Magellan GPS 315? I just started

this GPS stuff a week ago and could use some tips. I've noticed that 3

times the cache was located before I got to zero on my unit. Any tips? Have

you ever found a cache that had a location of zero? I noticed your Blue

Briefcase Cache read 42ft on my GPS.

 

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my response....

 

Hi Ray...

 

Thanks for the compliment, but trust me I've had my share of difficulties.

 

One thing I've found is that you should trust the gps...up to a point. That point, I feel, is about 50 feet. After that the cache is up to you. The fact is that two variable factors come immediately into play. The first is the readings taken by the cache hider. If they are off a bit, it will only be compounded when the cache seeker comes on the scene. The two people's gps devices are getting readings from different sats at the two different times.

 

If you want to pursue this issue, do this. Go to the middle of your front yard (or some spot) and take a reading...mark it as "home" or some such. You of course know exactly where you were standing when you took this reading and marked it. Now turn off the gps. Walk a few blocks away and then turn it on and punch the goto button. Follow your gps to your home. Walk at a moderate pace...especially when nearing your home. Watch the countdown on the gps. I have done this a number of times and I can be standing in "x marks the spot" and the gps will show I have 50 feet to go...or 20 feet to go, etc. Do it a few times and you will get different readings each time.

 

You can imagine this applies in the wild as well, with the only difference being you don't know where "x" is.

 

After finding a cache...with perhaps the gps showing 15 feet to go (or any figure), I have left it turned on, sitting on the cache, and over a period of time IT MIGHT come down to a few feet, or it may stay at 15 feet.

 

All of the above is why I believe the final 50 feet (or 30, or 22 or whatever) is up to the cache hunter. At American Kids Cache I had a reading of 3 feet and a terrain description that said I was right on top of it. Guess what...it was about 25 feet away. Same thing happened at Pepper's Blackberry. GPS said 20 feet to go; I looked down and there it was.

 

Hope these examples and suggestions give you a clue has to how I have done it.

 

Continue to enjoy the sport...there's always something new to learn and the exercise and outdoor envirornment is equally important as the hunt and the find...this seems to be a leading reason for doing geocaching...I know it is for me.

 

Ron

[Guest adventuretom]

I never expect to get zero, so the one time it happened it surprised the heck out of me. I was walking along watching the feet count down and then all of the sudden I had zero, which I had never seen. I was on a footbridge, so I looked under the bridge. By some fluke at that exact spot was the cache. Like most I typically get to about 25 feet and then start looking for the visual clues.

[Guest Nemesis]

quote:

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Originally posted by Ron Streeter:

...I offer this post.

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Ron, that was a very clear explanation of the effect of GPS error in geocaching.

 

We need more of that kind of thing for those just starting off.

 

Cheers,

Donovan.

[Guest Nemesis]

quote:

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Originally posted by Ron Streeter:

...I offer this post.

---

 

Ron, that was a very clear explanation of the effect of GPS error in geocaching.

 

We need more of that kind of thing for those just starting off.

 

Cheers,

Donovan.

[Guest mfratto]

On our first cache find, we were in fairly open spot and I hit zero, three different times at three slightly different locations.

 

That was a good lesson in final-leg accuracy.