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Dilution of Precision
DOP (dilution of precision) is a term used to describe the strength of a satellite configuration on the accuracy of data collected with GPS receivers. When satellites are bunched together in the same area of the sky view, the satellite geometry is termed "weak." The DOP will therefore be high in cases where satellites are directly overhead (bad), and low when the satellites are spread apart in the sky (good). Satellites that cannot be acquired due to landscape feature obstructions will weaken and increase the DOP.
VDOP (vertical dilution of precision) relates to the elevation measurements suggested by GPS data.
HDOP (horizontal dilution of precision) relates to the horizontal position measurements suggested by GPS data.
PDOP (positional dilution of precision) is most widely presented value in GPS receivers. This is the "mean" DOP value, and provides an overall rating of precision based on horizontal and vertical dilution of precision. The best PDOP value would be obtained with one satellite directly above the receiver and three others evenly spaced across the sky.
An upper limit on PDOP, beyond which no data will be collected, may be specified by users on some GPS receivers. On some GPS receivers, the default PDOP used is uncertain. While some suggest using a default PDOP mask of 6, when using a PDOP mask of 8, along with a SNR mask of 4, data collected with the Trimble GeoExplorer 3 meets national map accuracy standards when operating in forested conditions (Mancebo and Chamberlain 2001).
The table shown below suggests some general ranges of PDOP values and the approximate level of accuracy one might expect when collecting data under these conditions.
PDOP
value Comment on data quality
1 This PDOP provides the highest possible confidence in data accuracy, and is used for applications that demand the highest level of precision.
2-3 In this range, the positional measurements are accurate enough for all but the most sensitive applications.
4-6 This is the minimum level for mapping applications and for making business decisions.
7-8 Here, positional measurements could be used, but a better configuration of satellites is suggested.
9-20 Positional measurements with this PDOP provide low confidence in data quality.
21-50 Measurements using this PDOP range may be inaccurate by more than 150 feet
Dilution of Precision
DOP (dilution of precision) is a term used to describe the strength of a satellite configuration on the accuracy of data collected with GPS receivers. When satellites are bunched together in the same area of the sky view, the satellite geometry is termed "weak." The DOP will therefore be high in cases where satellites are directly overhead (bad), and low when the satellites are spread apart in the sky (good). Satellites that cannot be acquired due to landscape feature obstructions will weaken and increase the DOP.
VDOP (vertical dilution of precision) relates to the elevation measurements suggested by GPS data.
HDOP (horizontal dilution of precision) relates to the horizontal position measurements suggested by GPS data.
PDOP (positional dilution of precision) is most widely presented value in GPS receivers. This is the "mean" DOP value, and provides an overall rating of precision based on horizontal and vertical dilution of precision. The best PDOP value would be obtained with one satellite directly above the receiver and three others evenly spaced across the sky.
An upper limit on PDOP, beyond which no data will be collected, may be specified by users on some GPS receivers. On some GPS receivers, the default PDOP used is uncertain. While some suggest using a default PDOP mask of 6, when using a PDOP mask of 8, along with a SNR mask of 4, data collected with the Trimble GeoExplorer 3 meets national map accuracy standards when operating in forested conditions (Mancebo and Chamberlain 2001).
The table shown below suggests some general ranges of PDOP values and the approximate level of accuracy one might expect when collecting data under these conditions.
PDOP
value Comment on data quality
1 This PDOP provides the highest possible confidence in data accuracy, and is used for applications that demand the highest level of precision.
2-3 In this range, the positional measurements are accurate enough for all but the most sensitive applications.
4-6 This is the minimum level for mapping applications and for making business decisions.
7-8 Here, positional measurements could be used, but a better configuration of satellites is suggested.
9-20 Positional measurements with this PDOP provide low confidence in data quality.
21-50 Measurements using this PDOP range may be inaccurate by more than 150 feet
