DOP is an indicator of the quality of the geometry of the satellite constellation. The computed position can vary depending on which satellites use for the measurement. Different satellite geometries can magnify or lessen the errors in the error budget described above. A greater angle between the satellites lowers the DOP(2-3), and provides a better measurement. A higher DOP indicates poor satellite geometry, and an inferior measurement configuration.
Some GPS receivers can analyze the positions of the satellites available, based upon the almanac, and choose those satellites with the best geometry in order to make the DOP as low as possible. Another important GPS receiver feature is to be able to ignore or eliminate GPS readings with DOP values that exceed user-defined limits. Other GPS receivers may have the ability to use all of the satellites in view, thus minimizing the DOP as much as possible.
The special types of DOPs:
- VDOP Vertical DOP. Describes the effect of satellite geometry on height.
- HDOP Horizontal DOP. Indicates dilution of precision for horizontal positions.
- PDOP Position DOP. Combined vertical-horizontal position value.
- TDOP Time DOP. Time dimension effect of geometry.
- GDOP Geometric DOP. A composite measure of the vertical-horizontal-time dimensions.
Global Positioning System (GPS) 
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