The Position Dilution of Precision (PDOP) is used to characterize the relative positioning relationship between navigation satellite and user. The user's positioning accuracy can be simplified as PDOP*UERE. Under a fixed user error range, the smaller the PDOP, the higher the positioning accuracy.

Fig.1 GPS Position Dilution of Precision

DOP reflects the amplification effect to the user ranging error which is caused by spatial geometry of visible satellites and the receiver. When using pseudorange observations for dynamic absolute positioning, the weight coefficient matrix can be expressed as follows:

The definition of PDOP is as follows: