Definition of a SEM Almanac

Number of Records
The number of satellite almanac records contained in the file
Units: Records
Range: 0 to 32
Accuracy: 1
Precision: 2 significant digits
Frequency: Once per file
Type: Integer
Title
A short description of the file
Units: None
Range: Any combination of valid ASCII characters
Accuracy: None
Precision: 24 significant characters
Frequency: Once per file
Legality Checks: Valid ASCII characters
Type: ASCII string
GPS Week Number
The almanac reference week (VINA) for all almanacs in the file per IS-GPS-200H
Units: Weeks
Range: 0 to 1023
Accuracy: 1
Precision: 4 significant digits
Frequency: Once per file
Legality Checks: Range check
Type: Integer
GPS Time of Applicability
The almanac reference time (TOA) for all almanacs in the file per IS-GPS-200H
Units: Seconds
Range: 0 to 602112
Accuracy: 1
Precision: 6 significant digits
Frequency: Once per file
Legality Checks: Range check
Type: Long integer
PRN Number
The satellite PRN number per ICD-GPS-200H. This is a required data item as it is the GPS user's primary means of identifying GPS satellites. It is equivalent to the space vehicle identification (SVID) number of the satellite.
Units: None
Range: 1 to 32
Accuracy: None
Precision: 2 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Integer
SVN Number
The satellite "SVN" reference number. This is not a required data item and is normally included only for cross-reference with the operational control system (OCS).
Units: None
Range: 0 to 255
Accuracy: None
Precision: 3 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Integer
Average URA Number
The satellite "average" URA number, with URA number as defined in IS-GPS-200H. This is not an item in the raw almanac file but is based on the average URA value transmitted by this satellite in its subframe 1 data sets.
Units: None
Range: 0 to 15
Accuracy: 1
Precision: 2 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Integer
Eccentricity
The satellite almanac orbital "eccentricity" (e) as defined in IS-GPS-200H.
Units: Unitless
Range: 0.0 to 0.03
Accuracy: 4.7E-7
Precision: 7 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Real
Inclination Offset
The satellite almanac orbital "inclination angle offset" (i) as defined in IS-GPS-200H. This is an item in the raw almanac file and does not include the 0.30 semicircle reference value. This should not be confused with the "i0" term in the satellite ephemeris files.
Units: Semicircles
Range: -9.999999E-2 to +9.999999E-2
Accuracy: 1.91E-6
Precision: 7 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Real
Rate of Right Ascension
The satellite almanac orbital "rate of right ascension" (OMEGADOT) as defined in IS-GPS-200H.
Units: Semicircles/second
Range: -9.999999E-7 to +9.999999E-7
Accuracy: 3.6E-12
Precision: 7 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Real
Square Root of Semi-Major Axis
The satellite almanac orbital "square root of the semi-major axis" (A)1/2 as defined in IS-GPS-200H.
Units: Meters1/2
Range: 79.0 to 9999.99999
Accuracy: 4.8E-4
Precision: 9 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Real
Longitude of Orbital Plane
The satellite almanac orbital "geographic longitude of the orbital plane at the weekly epoch" (OMEGA)0 as defined in IS-GPS-200H.
Units: Semicircles
Range: -1.0 to +1.0
Accuracy: 1.1E-7
Precision: 9 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Real
Argument of Perigee
The satellite almanac orbital "argument of perigee" (ω) as defined in IS-GPS-200H.
Units: Semicircles
Range: -1.0 to +1.0
Accuracy: 1.1E-7
Precision: 9 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Real
Mean Anomaly
The satellite almanac orbital "mean anomaly" (M0) as defined in IS-GPS-200H.
Units: Semicircles
Range: -1.0 to +1.0
Accuracy: 1.1E-7
Precision: 9 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Real
Zeroth-Order Clock Correction
The satellite almanac zeroth-order clock correction term (af0) as defined in IS-GPS-200H.
Units: Seconds
Range: -9.9999E-4 to +9.9999E-4
Accuracy: 9.5E-7
Precision: 5 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Real
First-Order Clock Correction
The satellite almanac first-order clock correction term (af1) as defined in IS-GPS-200H.
Units: Seconds/second
Range: -9.9999E-9 to +9.9999E-9
Accuracy: 3.6E-12
Precision: 5 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Real
Satellite Health
The satellite subframe 4 and 5, page 25 six-bit health code as defined in IS-GPS-200H expressed in integer form.
Units: None
Range: 0 to 63
Accuracy: None
Precision: 2 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Integer
Satellite Configuration
The satellite subframe 4, page 25 four-bit configuration code as defined in IS-GPS-200H expressed in integer form.
Units: None
Range: 0 to 15
Accuracy: None
Precision: 2 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Integer

GPS SEM Almanacs
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Dr. T.S. Kelso [TS.Kelso@celestrak.com]
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Last updated: 2016 May 20 18:54:25 UTC
Accessed 39,749 times since 2000 December 16
Current system time: 2017 October 17 09:18:05 UTC