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DEFINITION OF A SEM ALMANAC

Theoretical almanac files are named using descriptive DOS file names that do not match the broadcast AL3 naming convention (e.g., PRIMEHI.AL3 would represent the Prime-21 high altitude constellation).

The almanac files each contain the following information:

Number of Records: The number of satellite almanac records contained in this *.AL3 file

Units: Records
Range: 0 to 32
Accuracy: I
Precision: 2 significant digits
Frequency: Once per file
Type: Integer

Title: A short description of this *.AL3 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 this *.AL3 file per ICD-GPS-200

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 this *.AL3 file per ICD-GPS-200
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-200.  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: I 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 ICD-GPS-200.   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 ICD-GPS-200.

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" (8i) as defined in ICD-GPS-200.   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
"lo" 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" (OMFGADOT) as defined in ICD-GPS-200.

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" (A1/2 as defined in ICD-GPS-200.

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" (OMEEGAO) as defined in ICD-GPS-200.

Units: Semicircles
Range: -1.0 to +1.0
Accuracy: 1.lE-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" ("small omega") as defined in ICD-GPS-200.

Units: Semicircles
Range: -1.0 to +1.0
Accuracy: I.lE-7
Precision: 9 significant digits
Frequency: Number of records per file
Legality check: Range check
Type: Real

Mean Anomaly: The satellite @ac orbital "mean anomaly" (MO) as defined in ICD-GPS-200.

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 (afo) as defined in ICD-GPS-200.

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 (afl) as defined in ICD-GPS-200.

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 ICD-GPS-200 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 ICD-GPS-200 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