My first cache find and my GPS is off a bit

[bailuck]

I have a new Meridian GPS and it seems to be off a bit. I located a cache and sat there for about ten minutes. My GPS unit indicated I was about 60 feet away from the spot. No trees were in the way, but the sky was very cloudy.

 

It was also off about 40 feet while standing at a benchmark.

 

Can anyone help me fix this or is there anything I can do?

[+Stunod]

How do you know the cache coords were right? Or the benchmark?

 

Truth is you don't, and those are fairly normal readings.

 

"Just because I don't care doesn't mean I don't understand."

[bailuck]

Well I assumed the coordinates were right from reading the online notes. Somebody posted that they found the cache a couple days ago and the coordinates led them straight to it.

 

I wouldn't have found the cache without the hint provided.

[+Searching_ut]

You can't tell at a cache if it's your GSS that is off, or the unit that recorded the position in the first place. Generally, it's a combination of the two

 

At the benchmark, you have to read the full datasheet to be sure the position of it is accurate. Even at an accurate benchmark, 40 feet of error would be in the range I would expect for non WAAS reception with this unit, although it's generally a little more accurate. If you're using WAAS, the unit tends to get more accurate and utilize the WAAS signals better if you give it 10 to 20 minutes of good WAAS reception first. (I have no idea why this is) 10 to even 20 minutes of averaging also tend to help improve accuracy.

[+brad.32]

You could have had a bad PDOP. What was the PDOP or the spread of the satellites you were locked onto?

 

If other people found the cache at the listed coords, then they are probably right. A normal, commercial GPS unit should have an accuracy of 5-10 m with a PDOP < 6. I've tested a number of different GPS units and they typically have ~5-m error. This is against each other or against accurate benchmarks, at the same time, and/or different days. Any benefit from averaging will be less than a minute. Long averaging is just waiting for a better PDOP.

 

Like Searching_ut said, the bottom line is, try some more caches and see how it performs.

[+EScout]

If you want to use a benchmark, be sure it is an "adjusted" benchmark. These are accurate to the centimeter, and listed in one hundred thousandth of a second in lat and lon.

 

See my posting:in the General section.

http://opentopic.Groundspeak.com/0/OpenTopic?a=tpc&s=1750973553&f=3000917383&m=2840994655

 

In this posting, you will find a link to the NGS site where you can get a list of these in your area. In a test of my Garmin Legend, I found the accuracy stunning, especially after adjusting for the rounding error when you enter the coords in your GPSr. Your GPSr only takes one thousandths of a minute. (This error should be less than four feet from the benchmark.)

[+Dersu]

quote:

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Originally posted by bailuck:

I have a new Meridian GPS and it seems to be off a bit..........

 

Can anyone help me fix this or is there anything I can do?

---

 

I have a Mag Merigreen and there is no adjustments you can make. It is either working or it isn't. Just be sure you are using the right datum (WGS84), waas is ON and you have the right coordintates entered in unit. There are so many variables to finding a cache that you have to look at it as an art or skill not a technology function of a GPSr.

Sometimes I find it helpful (once I find the area and think I am close) to back off 100 feet and walk staight to the area at a normal pace (about 2-3 MPH) from a direction that I have good or better signal strength. The GPSr can calculate your position better it seems, while you are moving.

Relax, trust your unit to get you close then use the hint if you have to or want to.

You may want to read about some of this on the

glossary page.

Happy Caching

 

I have flouted the wild, I have followed its lure, fearless. familar, alone; yet the wild must win,

and a day will come when I shall be overthrown. By: Robert Service