Do multiple GPSr's give a more accurate reading?

[+Fuchsiamagic]

I've just seen this comment in the Getting Started section which made me think:

 

"Trust your GPSr but don't give it total trust. If you go caching with three guys whom all have the same GPSr you'll be looking at three search areas several feet apart."

 

Now I wonder about this. I have two GPSr's and often take them both with me when out caching, however, I have noticed that they always both indicate EXACTLY the same position for GZ, whether they are together or 20 feet apart. This makes sense to me are they are dependent on the satellites positions which will always be the same, relative to each unit.

 

I would be interested in the experience of others.

[+Kryten]

The OP assumes that direct signals will be received from every satellite. In an open area this may be true but typical cache hiding locations include trees, cliffs, buildings, and other sources of reflection which can condiderably confuse the issue. Differences in receiver sensitivity may allow some units to maintain an accurate lock whilst others drift. Finally even for identical spec units, the longer a unit has been operating the more accurate it becomes since it's internal temperature calibration table will contains many more readings than that of a new unit.

[+StarBrand]

I own 7 different Garmin units and have taken them all out at the same time to compare readings. Ranging from the basic Blue eTrex Legend all the way up to the new Colorado 300. Sometimes 2 or 3 of the units will have the exactly the same readings but generally they are all slightly different. Usually no more than .004 minutes different but still different.

 

Just playing around one day I went back about 40 foot from a known cache and arranged all 7 in a circle around the cache and all the compass arrows were pointing right at the marked location - just had slightly different distance readings (35 to 44 feet).

 

Slightly different processors and software and antenna - all add up to make the subtle differences.

Edited April 3, 2008 by StarBrand

[+Flatouts]

We're a mixed Marriage Garmin & Magellan - they often differ sometimes a good bit - the really weird thing is the Magellan Explorist 500LE is usually right on the money?? The Garmin 60CSx seems to have more trouble in cover??

 

We were told to look 30' ahead at least of our GPSr - putting the units away at 30' from GZ and use Geosenses - sometimes this works the best.

 

If nothing else it helps us understand the hide better. (I still have a tenancy to look at mine - just as reference mind you...lol)

 

Vince of Flatouts

[+Stargazer22]

We have a Garmin 76Csx and a Vista Hcx.

They NEVER agree exactly. They are usually 15-20 feet apart, but they both typically get us to within 20 feet of the cache.

The 76Csx seems to be more accurate overall. However, there are times when the Vista Hcx puts us right on the cache.

[Ann_Brush]

A man with one watch knows what time it is, a man with two is never sure. To check the accuracy of any particular GPS unit take it to a USGS benchmark (or similar survey monument) with KNOWN and accurate position (many of them are for altitude not location).

[Neos2]

At an event, about 30 of us plugged a coordinate given to us by the event owner into our various units.

 

We went to the coordinates and placed a flag where we zeroed out.

 

The gps units all took us to the same general area. The swatch was about 15 feet wide, and not quite circular (slightly enlongated). Most of the group was within about 4 feet of each other. Only two people/units had the same zero spot. Those two had differnt models. Many people had identical models.

[+root1657]

We're a mixed Marriage Garmin & Magellan - they often differ sometimes a good bit - the really weird thing is the Magellan Explorist 500LE is usually right on the money?? The Garmin 60CSx seems to have more trouble in cover??

 

We were told to look 30' ahead at least of our GPSr - putting the units away at 30' from GZ and use Geosenses - sometimes this works the best.

 

If nothing else it helps us understand the hide better. (I still have a tenancy to look at mine - just as reference mind you...lol)

 

Vince of Flatouts

 

I've actually had a lot of luck with a different method if I'm having particular trouble at GZ. I back off 50-100 feet and get a sight line, then go 90 degrees or so off to one side and shoot another sight line. I pick the intersection in my head, and it usually works out real well.

 

Some of my cache buddies have trouble understanding why I search 30 feet from where they zero out, but darned if it dont work a lot.

[+TotemLake]

I've just seen this comment in the Getting Started section which made me think:

 

"Trust your GPSr but don't give it total trust. If you go caching with three guys whom all have the same GPSr you'll be looking at three search areas several feet apart."

 

Now I wonder about this. I have two GPSr's and often take them both with me when out caching, however, I have noticed that they always both indicate EXACTLY the same position for GZ, whether they are together or 20 feet apart. This makes sense to me are they are dependent on the satellites positions which will always be the same, relative to each unit.

 

I would be interested in the experience of others.

No. But you will have a better opportunity to average the location.