Dilution of precision (GPS)

Dilution of precision (DOP), or geometric dilution of precision (GDOP), is a term used in satellite navigation and geomatics engineering to specify the additional multiplicative effect of navigation satellite geometry on positional measurement precision.

The concept of dilution of precision (DOP) originated with users of the Loran-C navigation system. The idea of Geometric DOP is to state how errors in the measurement will affect the final state estimation. This can be defined as:

${\displaystyle GDOP={\frac {\Delta ({\rm {Output\ Location}})}{\Delta ({\rm {Measured\ Data}})}}}$

Conceptually you can imagine errors on a measurement resulting in the ${\displaystyle \Delta ({\rm {Measured\ Data}})}$ term changing. Ideally small changes in the measured data will not result in large changes in output location, as such a result would indicate the solution is very sensitive to errors. The interpretation of this formula is shown in the figure to the right, showing two possible scenarios with acceptable and poor GDOP.

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