Estimated position error
Estimated Position Error (also known as EPE) is a GPS reciever's estimate of it's own inaccuracy at the moment.
For example: When your GPSr tells you the EPE is 40 feet, what it is really saying is "I am pretty sure I know where we are. . . give or take 40 feet".
Some GPS receivers will also display HEPE which stands for Horizontal Estimated Position Error. HEPE is an EPE without considering the inaccuracy of your altitude reading. Because of the inherent difficulty of calculating altitude with GPS, an HEPE is usually a smaller number than EPE. Since most geocaches are located on the earth's surface, your HEPE is more relevant to your search anyway.
- Note: Some GPS recievers do not display both. If your GPS only displays EPE, it is probably in reality an HEPE reading.