# USNO GPS Data Categories Explanation

USNO GPS Data Categories Explanation

**USNO GPS Data Categories Explanation**

Column | Data Category | Explanation |
---|---|---|

1 | PRN | the satellite vehicle PRN number |

2 | MJD | the five digit Modified Julian Date and the fraction of day at the midpoint of the track |

3 | BGTK HHMM |
hour and minute (in UTC) of the start of the track tracks begin at 1 second after the minute |

4 | TRK SEC |
the track length in seconds (a full track is 780 seconds) |

5 | MC-GPS NS |
the time difference (measured in nanoseconds) between UTC(USNO MC) and GPS time, referred to the midpoint of the pass via a linear fit |

6 | SLOPE PS/S |
the slope determined via the linear fit to produce MC-GPS (measured in picoseconds per second) |

7 | RMS NS |
the root mean square of the residuals of the linear fit used to produce MC-GPS |

8 | SAMP N |
the number of data points used in the fit to produce MC-GPS |

9 | EL DG |
the elevation (in degrees) of the satellite at the midpoint of the track (data prior to MJD 50846 gives elevation at beginning of track) |

10 | AZM DEG |
the azimuth (in degrees) of the satellite at the midpoint of the track (data prior to MJD 50846 gives azimuth at beginning of track) |

11 | ION NS |
the modeled ionospheric delay (measured in nanoseconds) referred to the midpoint of the pass via a linear fit |

12 | MC-SATCL NS |
the time difference (measured in nanoseconds) between UTC(USNO MC) and satellite time, referred to the midpoint of the pass via a linear fit |

13 | SLOPE PS/S |
the slope determined via the linear fit to produce MC-SATCL (measured in picoseconds per second) |

14 | TROP NS |
the modeled tropospheric delay (measured in nanoseconds) referred to the midpoint of the pass via a linear fit |