Glossary
Appendix B
GSR2600
97
roving user from one or more reference stations. Static
differential GPS involves determining baseline vectors between
pairs of receivers.
Dilution of Precision (DOP) -
The geometry of the visible
satellites is an important factor in achieving high quality results.
The geometry changes with time due to the relative motion of
the satellites. An accuracy measure for the geometry is the
Dilution of Precision (DOP) factor.
DOP is a description of the effect of satellite geometry on
position and time computations. Values that are considered to
be 'good' are small, approximately 3. Values greater than 7 are
considered poor. Thus, a small DOP is associated with widely
separated satellites. Standard DOP terms for GPS include:
Doppler -
The change in frequency of sound, light or other wave
caused by movement of its source relative to the observer.
GDOP (Geometric
Dilution of Precision)
GDOP is a composite measure reflecting
the effects of satellite geometry on position
and time computations.
PDOP (Position
Dilution of Precision)
PDOP reflects the effects of satellite
geometry on position computation.
HDOP (Horizontal
Dilution of Precision)
HDOP reflects the effects of satellite
geometry on the horizontal component of
the position computation.
HTDOP (Horizontal
Position and Time
Dilution of Precision)
2D parameters and time are uncertain
(latitude, longitude, time). The lower the
HTDOP value, the greater the confidence
factor.
VDOP (Vertical
Dilution of Precision)
VDOP reflects the effects of satellite
geometry on the vertical component of the
position computation.
TDOP (Time Dilution
of Precision)
TDOP reflects the effects of satellite
geometry on the time computation.
NDOP (North Dilution
of Precision)
This is related to GDOP. It describes the
effects of geometry on the northern
component of positioning accuracy.
750-1-0093 Rev 1.book Page 97 Friday, June 28, 2002 4:02 PM
