How Do You Calibrate A Garmin Gpsr?
My Garmin GPSr is between 50 and 80 feet off. Does anyone know what might be wrong. Is there a time difference that must be added into the software? It is a etrex Legend Cx.
When I bought it, it worked fine and now, 6 months later, it is way off. It make geocaching impossible. Please help.
You cannot calibrate a GPS. It is possible for some very high end units to receive additional signals that can improve the accuracy to a few inches. Some of them can have a correction factor to record a position other than its antenna.
GPS signals are blocked many things including anything that contains water such as leaves, your body, or heavy cloud cover.
Your quality of measurement depends on where the satellites are in the sky, if anything is between the receiver and the satellites (trees, your body), and how good the receiver is at picking up weak signals.
The numbers you are seeing are very likely when looking for a cache. Watch the accuracy numbers on your GPS when looking for a cache and see how it varies with different amount of tree cover. With my old Etrex Vista (no letters) 50 feet would not be uncommon in woods. The H series units have a new receiver in them that will cut that in half. I bought a Vista HCx last fall and am amazed where it will get a good signal.
You also have to consider that the person who placed the cache most likely did not have a better GPS than you have. It is likely to be an older generation and be even less accurate. The formula for combined accuracy of two equal units is to multiply the reading you see by 1.4
You also have to realize that the number that your GPS gives you is not a limit. It is a statistical measure and you will occasionally be outside of it. (By comparing multiple tracks of the same routes, I personally think that Garmin’s calculation is a bit on the optimistic side).
You are not expected to be able to walk up to the final position by GPS and reach out to grab the cache.
They put the notes in the listings for a purpose, to help you find it in the circle of uncertainty around it. Especially since most people hide them a bit so that they are not obvious.