A Word About The Accuracy of PREDICT
====================================

In 2007, the TEME ECI position vectors generated by PREDICT were compared
against a "proven" and well-respected SGP4 model used at the U.S. Naval
Research Laboratory, as well as an academic orbital model available through
thecenterforspace.com.

The test was performed on one TLE for a very long duration to measure the
difference in behavior between the predictions made through PREDICT and
the other satellite predictors.  The duration was between the start of
the TLE epoch at 03:34:00 UTC on 26-March-2007, and ran through
03:34:00 UTC on 17-July-2007.

Using a time step of one minute, 159841 samples were taken.  The mean
position error produced by PREDICT was 0.003982 km.  The mean velocity
error was 0.000006 km/s.

The minimum position error was 0.001463 km.  The maximum position error
was 0.006669 km.  The standard deviation was 0.001137 km.  The mean velocity
of the spacecraft was 7.484321 km/s, and the mean time error was 0.000532
seconds.

The model available through thecenterforspace.com produced a mean error in
the single km range.  While this accuracy is very good, it is not as good
as the meter resolution produced by PREDICT.

The orbital models used in PREDICT were derived from "satcom-08", written
by Neoklis Kyriazis, 5B4AZ, and released in 2002 under the GNU General
Public License.  Parts of "satcom-08" were derived through a translation
into 'C' of SGP4 and SDP4 code written originally in FORTRAN and Pascal
by Dr. T.S. Kelso.

Further news about PREDICT can be found on the web at:

	https://www.qsl.net/kd2bd/predict.html

