## GPSThe data are placed in files called Older data files (1994-2011) you can find here: health_a.gps, iono.gps, iono_a.gps. ## Organization of status.gps file:The content of this file is in development. At present this file contains just numbers of launched satellites, changes in their configuration, and inserting or removing the satellite from the almanac. We are going to keep this file up to date. ## Organization of ionospheric parameters:
The file ## Organization of satellite health drop-outs file:
In the file ## Organization of almanac data:
The almanac data are the subset of the clock and ephemeris parameters with reduced precision. The almanac parameters are updated usually at least once a week. We will update the almanac as quickly as possible. You should find the newest almanac in
The file - Header
- UTC and ionosphere data
- Satellites data
***** 1) HEADER ***** The header of this file is self explaining. Example: ALMANAC was received on 14 Jan 1994, 12:45:21 UTC ***** 2) UTC AND IONOSPHERE DATA ***** UTC and IONO blocks contain coefficients from page 18 of subframe 4. UTC block begins with a keyword "UTC:". It contains the parameters needed to relate GPS time to UTC (USNO) time: A/1 First order term of polynomial units [s/s]; range approx. (-7.5ns/s, 7.5ns/s) A/0 Constant term of polynomial units [s]; range approx. (-2s, 2s) t/ot Reference time for UTC data units [s]; range (0, 602112) WN/t UTC reference week number units [weeks]; range (0, 1023) DELTA_t/LS Time difference due to leap seconds units [s]; range (-128, 127) WN/LSF Week number at the end of which the leap seconds become effective units [weeks]; range (0, 1023) DN Day number at the end of which the leap seconds become effective units [days]; range (1, 7) DELTA_t/LSF Difference due to leap seconds units [s]; range (-128, 127) IONO block begins with a keyword "IONO:". It contains current coefficients for eight-coefficient (Klobuchar) model of ionosphere: alpha/0..3 four alfa coefficients units [s s/semicircle s/semicircle^2 s/semicircle^3]; ranges approx. (+-120ns) (+-954ns/semicircles) (+-7.6us/semicircles^2) (+-7.6us/semicircles^3) beta/0..3 four beta coefficients units [s s/semicircle s/semicircle^2 s/semicircle^3]; ranges approx. (+- 260000) (+-2100000) (+-8400000) (+-8400000) Example: UTC: A/1 = 4.707346E-0014 A/0 = 1.862645E-0008 t/ot = 118784 WN/t = 732 DELTA_t/LS = 9 WN/LSF = 703 DN = 3 DELTA_t/LSF = 9 IONO: alpha/0..3 = 1.117587E-0008 -7.450581E-0009 -5.960464E-0008 1.192093E-0007 beta/0..3 = 1.146880E+0005 -1.638400E+0005 -1.966080E+0005 9.175040E+0005 ***** 3) SATELLITES DATA ***** These data come from subframe 4 (pages 2 through 5 and 7 through 10 and page 25) and subframe 5 (all pages). Satellite data begin with a keyword "ALM:". Satellites are distinguished from each other by an empty line. SV_ID Space vehicle - satellite identifier [dimensionless]; range (1, 32) A-S Anti-Spoofing; P-code encryption (ON, OFF) Block Configuration of satellite (1, 2) Health 8-bits health word (the 5 LSB bits provide the health status of signal components and 3 MSB bits (range 0..255) The meaning in the health word is translated to readable form (BAD/GOOD) in parantheses behind the value t/oa Reference time of almanac units [seconds in week]; range (0..602112) step 4096 WN/a Reference week of almanac units [weeks]; range (0, 1023) e Eccentricity [dimensionless]; range approx. (0, 0.032) i Inclination angle units [semicircles]; range approx.(0.23, 0.37) sqrt(A) Square root of the semi-major axis units [metres^1/2]; range approx. (0, 8200) OMEGA/0 Longitude of ascending node of orbit plane at weekly epoch units [semicircles]; range (+-1) OMEGA_DOT Rate of right ascension units [semicircle/second]; range (+-120e-9) omega Argument of perigee units [semicircles]; range (+-1) M/0 Mean anomaly at reference time units [semicircles]; range (+-1) a/f0 Satellite PRN code phase time offset units [s]; range (+-1ms) a/f1 Satellite PRN code relative frequency offset units [s/s]; range approx. (+-4ns/s) N.B. 1 semicircle= 1 rad/PI Example: ALM: SV_ID = 1 A-S = OFF Block = 2 Health = 0 ( Signal = GOOD , Data = GOOD ) t/oa = 118784 WN/a = 732 e = 3.47614288330078E-0003 i = 3.00995635986328E-0001 sqrt(A) = 5.15362451171875E+0003 OMEGA/0 = 4.99201297760009E-0001 OMEGA_DOT = -2.53930920735001E-0009 omega = -3.57437849044800E-0001 M/0 = -5.23125290870666E-0001 a/f0 = -4.57763671875000E-0005 a/f1 = -2.03726813197136E-0010 SV_ID = 2 A-S = OFF Block = 2 Health = 0 ( Signal = GOOD , Data = GOOD ) t/oa = 118784 ... etc. |