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R E A L - T I M E I O N O S P H E R I C C O R R E C T I O N S ( R T I C )
Our Proprietary Solution
The GPS code modulation and carrier phase delays are affected differently as they propagate through
the ionosphere. By recognizing a few other aspects of this behavior, EndRun developed the RTIC
algorithm to directly quantify the delay through the ionosphere, and resolve the code phase and car-
rier phase bias. The bias information enables real-time measured delay compensation in EndRun’s
proprietary, single-frequency, L1 GPS receiver.
To our knowledge, this capability is unique to End-
Run Technologies
.
The algorithm is effective when the receiver is operating at a stationary location with continuous
tracking of at least one satellite at all times. After a 24-hour initialization period it begins producing
real-time ionospheric delay measurements, with full accuracy of those measurements achieved after
several days. When ionospheric conditions are quiet or relatively normal, this option improves the
accuracy and stability of the timing outputs by as much as a factor of three at observation intervals
between 3,000 and 100,000 seconds. During a major ionospheric storm event, the improvement
may be much greater. It is very difficult to achieve this stability over these observation intervals by
another method, as only a high-performance cesium frequency standard is stable enough to act as a
filter for the timing errors caused by the GPS broadcast model. The following phase plot shows the
Meridian II / RTM3205 with the RTIC option active (blue) compared to what the performance would
have been using the GPS broadcast model (red). Throughout the 10-day test period the RTIC option
demonstrated substantial improvement to frequency and time-domain stability through real-time
ionospheric delay measurements and compensation.
Summary of Contents for RTM3205
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