Aero-Terms are designed to be a daily reminder of the terms,
names, acronyms and explanations of the unique language that
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any intriguing terms.
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DGPS (Differential Global
DGPS achieves enhanced accuracy since the reference and user
receivers both experience common errors that can be removed by the
user. Position errors less than 10 meters are typically
In the basic form of DGPS, the position of a reference receiver
at a monitoring or reference station is surveyed in, that is, its
position is known accurately. The user receiver should be no more
than about 300 miles away from the reference receiver which makes
pseudorange measurements, just as any user receiver would. However,
because the reference receiver knows its position accurately, it
can determine “biases” in its pseudorange measurements.
For each satellite in view of the reference receiver, these biases
are computed by differencing the pseudorange measurement and the
satellite-to-reference receiver geometric range. These biases
incurred in the pseudorange measurement process include errors
arising from ionospheric delay, tropospheric delay, and satellite
clock offset from GPS time. For real-time applications, the
reference station transmits these biases, called differential
corrections, to all users in the coverage area of the reference
station. Users incorporate these corrections to improve the
accuracy of their position solution.
For the basic local area DGPS (LADGPS) the position solutions of
users further away from the reference station are less accurate
than those closer to the monitoring station because pseudorange
measurement errors tend to be spatially correlated. This loss of
accuracy due to spatial decorrelation can be improved with more
sophisticated techniques that fall under the heading of wide area
DGPS (WADGPS) such as WAAS.