My coords. have changed!!! What gives???

[Guest sdstack]

able batteries today and I wasn't yesterday. My unit is WAAS compatable and I waited for it to average yesterday. The weather was exactly the same both days and the batteries were equally charged. Any suggestions???

[Guest arffer]

Your GPSR may be WAAS capable, but did you have WAAS turned on, and did you have a WAAS lock?

 

If you did, and on both days, then I have no idea why that big of a variance.

 

But if you didn't, on either or both days, the 50-75 feet is well within the accuracy of the GPSR. Check out my diagram HERE

 

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Team CacheCows of Wisconsin

[Guest mikechim]

I'm completely bull******* on this one but could it have anything to do with the time of day you went out? Maybe there were less satellites that your gps was able to get a fix on since they are orbting the earth and are not in the same place at all times... not sure if that's a possibility or not, maybe someone with more knowledge could help ya.

[Guest Kerry]

quote:

---

Originally posted by arffer:

Check out my diagram HERE

---

 

arffer, in the new world the accuracy spec's now are global average <= 13 metres and worst case scenario <=36 metres @ 95% but both those are signal in space [sIS) figures. I suppose 15m is still close but no more Repeatable Accuracy what a shame .

 

Cheers, Kerry.

[Guest Kerry]

quote:

---

Originally posted by arffer:

Check out my diagram HERE

---

 

arffer, in the new world the accuracy spec's now are global average <= 13 metres and worst case scenario <=36 metres @ 95% but both those are signal in space [sIS) figures. I suppose 15m is still close but no more Repeatable Accuracy what a shame .

 

Cheers, Kerry.

[Guest CharlieP]

Do you know what the EPE (Estimated Position Error) accuracy reading from your GPS was on each day? If your GPS can only lock on 4 or 5 satellites and the geometry is not good because of obstructions (hills and trees) your GPS can have a substantial error, even more than 75 feet. When placing a cache it is best to use coordinates taken when the EPE is low, and for better accuracy take several readings at different times and average them.

 

FWIW,

CharlieP

[Guest sdstack]

Thanks for the info, but... On one spot (where I paid attention to the accuracy within screen, I had an accuracy within 9 feet both days. I was on top of a siloh with clear blue skies and not a tree in sight. I can't speak for the other points and their accuracy because I didn't pay attention either day.

[Guest arffer]

quote:

---

Originally posted by Kerry:

arffer, in the new world the accuracy spec's now are global average <= 13 metres and worst case scenario <=36 metres @ 95% but both those are signal in space [sIS) figures. I suppose 15m is still close but no more Repeatable Accuracy what a shame .

 

Cheers, Kerry.

---

 

Hi Kerry,

 

I'm afraid that I'm missing your point. My diagram is based on the listed specifications for the majority of the non-WAAS GPSRs published by the manufacturers: 15 meters.

 

I see that some of the newer specs are now listing the accuracy as <15 meters 95% of the time, but they aren't diferentiating between WAAS and non-WAAS it seems.

 

This original figure of 15 meters was the BEST case scenerio of a consumer, non-WAAS GPSR, the accuracy (dependent on a number of items) could be worse.

 

Based on your post, what are you desiring I base my diagram on, 13 meters? 36 meters? or some average?

 

I'm sure willing to modify the diagram if I can see that the 15 meter figure is wrong. I just pulled up the specs on my maggy 315 to check, and they still are listed as 15 meters. The new Garmin V is listed as <15 meters 95% of the time, but there is no statement as to how far under 15 meters, what are you supposed to use? 14.999 meters, or .999 meters; both are by definition <15 meters.

 

Looking forward to your comments, thanks!

[Guest arffer]

quote:

---

Originally posted by Kerry:

arffer, in the new world the accuracy spec's now are global average <= 13 metres and worst case scenario <=36 metres @ 95% but both those are signal in space [sIS) figures. I suppose 15m is still close but no more Repeatable Accuracy what a shame .

 

Cheers, Kerry.

---

 

Hi Kerry,

 

I'm afraid that I'm missing your point. My diagram is based on the listed specifications for the majority of the non-WAAS GPSRs published by the manufacturers: 15 meters.

 

I see that some of the newer specs are now listing the accuracy as <15 meters 95% of the time, but they aren't diferentiating between WAAS and non-WAAS it seems.

 

This original figure of 15 meters was the BEST case scenerio of a consumer, non-WAAS GPSR, the accuracy (dependent on a number of items) could be worse.

 

Based on your post, what are you desiring I base my diagram on, 13 meters? 36 meters? or some average?

 

I'm sure willing to modify the diagram if I can see that the 15 meter figure is wrong. I just pulled up the specs on my maggy 315 to check, and they still are listed as 15 meters. The new Garmin V is listed as <15 meters 95% of the time, but there is no statement as to how far under 15 meters, what are you supposed to use? 14.999 meters, or .999 meters; both are by definition <15 meters.

 

Looking forward to your comments, thanks!

[Guest arffer]

quote:

---

Originally posted by sdstack:

Thanks for the info, but... On one spot (where I paid attention to the accuracy within screen, I had an accuracy within 9 feet both days. I was on top of a siloh with clear blue skies and not a tree in sight. I can't speak for the other points and their accuracy because I didn't pay attention either day.

---

 

EPE is the estimated position error based on the geometery and signal of the sattelite constellation your GPSR is receiving. This EPE is in addition to the basic inaccuracy of your GPSR, it gets added to how far off your GPSR can be just based on the fact that you paid <$10,000 for it.