Caching With Friends

[schmism]

How many out there go chacheing with friends that also have GPS? Do you find that even 2 units of the same type will read diffrent? How about accross platform?

 

I have a buddy that has a diffrent version than mine and half the time it seems like im "off" and the other half the time it seems he is.

 

second question

 

Is differential measurement with a GPS more accurate than the readings themselves?

 

from point A walk 20 meters to point B (via "distance" on the GPS) now if you know there is some amount of uncertainty about point A and you assume the same uncertainty for B Then do the uncertainties cancel out? and leave you with a (arguably) accurate distance measurement?

[+Tubby Rower]

How many out there go chacheing with friends that also have GPS? Do you find that even 2 units of the same type will read diffrent? How about accross platform?

 

I have a buddy that has a diffrent version than mine and half the time it seems like im "off" and the other half the time it seems he is.

 

I've had 3 and 4 GPSr's reading the same measurements and all of them were off of the real coordinates. I've also had the same GPSr's read differnt readings. The inaccuracies could be off in different directions.

 

Then do the uncertainties cancel out? and leave you with a (arguably) accurate distance measurement?

 

Not necessarily. The "accuracy circle" is just that a circle. Point A in your above scenario could be 20 ft off to the North and point B could be off the same 20 ft to the South. Therefore in this case you'd be 40 ft. off even the the accuracies are the "same".

 

You should try triangulating the point by walking away from the desired loactions area and looking at the bearing and distance. do this for 3 or 4 different directions and then all of those points should cross each other within a reasonable distance. See Markwell's FAQ on Triangulation.