README.md

gps-sem-parser

Example

  import sem from 'gps-sem-parser';
  const almanac = sem( rawAlmanac );

{
  "gpsWeek": 1844,
  "toa": 405504,
  "epoch": 1115656704,
  "satellites": [
    {
      "prn": 1,
      "svn": 63,
      "ura": 0,
      "eccentricity": 0.00419855117797852,
      "inclination": 0.9617664060621093,
      "rightAscensionDot": -8.114623720935037e-9,
      "semimajorAxis": 26559649.327529907,
      "rightAscension": -1.6779199426606246,
      "argumentOfPeriapsis": 0.37559459670255485,
      "meanAnomaly": -2.781213528432701,
      "clockBias": -0.0000057220458984375,
      "clockDrift": 0,
      "health": 0,
      "config": 11
    }
  ]
}

API

sem(file, gpsEpoch)

Parses a string containing a GPS almanac in sem format. Pass gpsEpoch with the number of times the gps week has rolled over. Set gpsEpoch to null and year to the year in which the almanac was issued to try to automatically resolve the gps epoch. (Defaults to current year)

Return an Almanac object.

Parameters

name	type	description
file	string	Almanac in SEM format
gpsEpoch	number	(optional) Number of times the GPS Week index rolled over.
year	number	(optional) Year in which the Almanac was issued (to resolve gps epoch). )

Almanac

Object representing a GPS almanac

name	type	description
gpsWeek	number	GPS Week of the almanac
toa	number	Time of Applicability of the alamanc
epoch	number	Epoch of the almanac (seconds since start of GPS time)
satellites	[Satellite]	Array of satellite element sets

Satellite

Object representing a satellite element set. (For details see IS-GPS-200)

name	type	description
prn	number	Assigned PRN
svn	number	Space Vehicle Number
ura	number	User Range Accuracy
eccentricity	number	Eccentricity at epoch
inclination	number	Inclination at epoch (rad)
rightAscensionDot	number	First derivative of the right ascension (rad/s)
semimajorAxis	number	Semimajor Axis at epoch (m)
rightAscension	number	Right ascension at start of GPS Week (rad)
argumentOfPeriapsis	number	Argument of periapsis (rad)
meanAnomaly	number	Mean Anomaly at epoch (rad)
clockBias	number	Clock bias at epoch (s)
clockDrift	number	Clock drift at epoch (s/s)
health	number	Health of satellite
config	number	Configuration of satellite