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Maritime Information

ID: PRN of the SVN

Health: 000=usable

Eccentricity: This shows the amount of the orbit deviation from circular (orbit). It is the distance between the foci divided by the length of the semi-major axis (our orbits are very circular).

Time of Applicability: The number of seconds in the orbit when the almanac was generated. Kind of a time tag.

Orbital Inclination: The angle to which the SV orbit meets the equator (GPS is at approx. 55 degrees). Roughly, the SV's orbit will not rise above approx. 55 degrees latitude. The number is part of an equation: #= pi/180 = the true inclination.

Rate of Right Ascension: Rate of change in the measurement of the angle of right ascension as defined in the Right Ascension mnemonic.

SQRT(A) Square Root of Semi-Major Axis: This is defined as the measurement from the center of the orbit to either the point of apogee or the point of perigee.

Argument of Perigee: An angular measurement along the orbital path measured from the ascending node to the point of perigee, measured in the direction of the SV's motion.

Mean Anomaly: Angle (arc) traveled past the longitude of ascending node (value= 0-180 degrees or 0-negative 180 degrees). If the value exceeds 180 degrees, subtract 360 degrees to find the mean anomaly. When the SV has
passed perigee and heading towards apogee, the mean anomaly is positive.After the point of apogee, the mean anomaly value will be negative to the point of perigee.

Af(0): SV clock bias in seconds

Af(1): SV clock Drift in seconds per seconds

week: GPS week (0000-1024), every 7 days since 22 Aug 1999