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Gps Coordinates?


SCCS
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I am wondering how close does the gps unit gets you to the actual spot like a cache. We have found a couple of caches ;) and they were about 30'ft from the coordinates. :lol: How accurate are the new units like the GARMIN 70csx or the 60csx.

They would be about the same, the caches were hidden with non sirf III units. there is no way a Sirf III gps is going to get you any closer to a cache that was hidden with a non Sirf III GPS. Some cachers may trick them selves into think they wil, but they will not.

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Here's a link to the Sirf III spec from Sirf. Sirf III Spec Notice that its attributes are better sensitivity in low signal areas (getting close to what Magellan has always had under trees), faster time to first fix, small size so it can fit in cell phones, and low power consumption.

 

Accuracy of measurement is not one of those. And there is a reason for that. The accuracy is limited by the GPS satellite system not the chip set. The GPS satellite system only allows about 3 meter (10ft) accuracy on the civilian channels. That's because its a US military system that provide less than 1m accuracy on its military signal and not its civilian. In real life performance, 20-30' accuracy is good.

 

So non-SirfIII and SirfIII makes no differenc in position accuracy but does in ability to receive the satellites. What will make a position accurcy difference is EGNOS when its fully deployed. Its a civilian system rather than military and is specified to 1 meter accruacy for civilian use. Then the EGNOS cabilities of SirfIII will make a difference.

 

As proof, I have a Magellan Platinum and a BT-338 SirfIII system and they show the same sensitivity under trees and display position coordinates in the field.

 

JDandDD

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Here's a link to the Sirf III spec from Sirf. Sirf III Spec Notice that its attributes are better sensitivity in low signal areas (getting close to what Magellan has always had under trees), faster time to first fix, small size so it can fit in cell phones, and low power consumption.

 

Accuracy of measurement is not one of those. And there is a reason for that. The accuracy is limited by the GPS satellite system not the chip set. The GPS satellite system only allows about 3 meter (10ft) accuracy on the civilian channels. That's because its a US military system that provide less than 1m accuracy on its military signal and not its civilian. In real life performance, 20-30' accuracy is good.

 

So non-SirfIII and SirfIII makes no differenc in position accuracy but does in ability to receive the satellites. What will make a position accurcy difference is EGNOS when its fully deployed. Its a civilian system rather than military and is specified to 1 meter accruacy for civilian use. Then the EGNOS cabilities of SirfIII will make a difference.

 

As proof, I have a Magellan Platinum and a BT-338 SirfIII system and they show the same sensitivity under trees and display position coordinates in the field.

 

JDandDD

What other type of coordinates can be displayed in the field?

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What will make a position accurcy difference is EGNOS when its fully deployed. Its a civilian system rather than military and is specified to 1 meter accruacy for civilian use. Then the EGNOS cabilities of SirfIII will make a difference.

EGNOS is just the European version of WAAS (both are examples of SBAS systems) and works in conjunction with the GPS system to give nominal accuracy of 3m. Actual performance under ideal conditions has actually tested somewhat better than this for WAAS and I'd expect the same for EGNOS. Almost all of the current GPS receivers from Garmin, Magellan, Lowrance, and most manufacturers are already compatible with WAAS and EGNOS so the SIRF III chips have no special significance there.

 

You may be thinking of the European Galileo system that's in very preliminary stages (first testbed satellite was just launched this month). That promises to give somewhat better accuracy than the current GPS system. Of course by the time Galileo is actually deployed (2010 by the current schedule) the GPS system is also planned to be improved with additional frequencies giving better accuracy. But, AFAIK, SIRF is not promising that their current chipsets will work with either Galileo or the future GPS enhancements (although SIRF is an active participant in the Galileo consortium).

 

I expect we'll all have to buy new receivers to take advantage of the capabilities of Galileo and the next phase of GPS and who knows what manufacturer will have the best chipset by the time those systems are available.

 

OTOH, from what I've seen the sensitivity of the SIRF III chips is considerably better than anything offered up to now by Garmin, Magellan, or Lowrance.

 

To the original poster:

30' is not unusual, especially considering that it's the combination of the error by the original placer of the cache and that of the finder. Since the satellite configuration constantly changes the errors may well be in opposite directions. Many caches are also placed where reception conditions are far from ideal (obstructions of part of the sky, overhanging foliage, sources of multipath reflections, etc.) which can further reduce accuracy.

Edited by peter
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Here's a link to the Sirf III spec from Sirf. Sirf III Spec Notice that its attributes are better sensitivity in low signal areas (getting close to what Magellan has always had under trees), faster time to first fix, small size so it can fit in cell phones, and low power consumption.

Hmmm. Thanks. OK, I'll just wait until it's out there enough that there's a good feel for what the real-world difference is.

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Back to the original question. You have to take into account the hider may not have been really accurate with his coordinates to begin with, so you could be dealing with to errors instead of just one. With that being said I have many times been within 1 foot of the cache when I zeroed. One thing to I do is not get in a hurry. When the GPS says zero I look around, but don't assume that this is going to be its final zeroeing point. After 5 or ten minutes it often has me more a ways to a new location as zero. This is normally the spot where it is most accurate. At the same time the furthest off I have been is 1/2 mile. that was because the cache owner had inverted a couple of numbers when he posted his cache. I never would have found it if a previous finder had not listed the correct corrdinates.

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