Dilution of Precision Scale

Table of HDOP ranges and their associated meanings. When establishing the accuracy of our GNSS (GPS) fix, we need to understand the Dilution of Precision (DOP), sometimes referred to as Horizontal Dilution of Precision (HDOP). This is provided as a number of 1 or greater. The lower the number, the more accurate the fix.

Dilution of precision (DOP), or geometric dilution of precision (GDOP), is used in satellite navigation and geomatics engineering to specify the additional multiplicative effect of navigation satellite geometry on positional measurement precision. The precision of multiple satellites in view of a receiver combine according to the relative position of the satellites to determine the level of precision in each dimension of the receiver measurement. When visible navigation satellites are close together in the sky, the geometry is said to be weak, and the DOP value is high; when far apart, the geometry is strong, and the DOP value is low.

This downloadable table outlines the likely position accuracy based on the receiver’s reported DOP number.