PositionVelocityTime.jl

Calculates position, velocity, and time from GNSS satellite measurements.

Features

• Estimation of user position, velocity, and time
• Satellite position and velocity calculation from orbital parameters (LNAV and CNAV/CNAV-2 quasi-Keplerian ephemerides)
• Dilution of Precision (DOP) computation
• Support for GPS (L1 C/A, L2C, L5, L1C) and Galileo (E1B, E5a), including combined multi-GNSS solutions. Each measurement is one satellite-band pseudorange; the group-delay/ISC correction is selected by the signal the range was generated on (which may be a pilot such as GPS L1C-P or Galileo E1C), while the ephemeris and clock come from the band's data-component decoder.

Installation

using Pkg
Pkg.add("PositionVelocityTime")

Quick Start

Decoded data and code phase of a satellite must be combined in the SatelliteState struct:

using PositionVelocityTime, GNSSSignals, GNSSDecoder

gpsl1 = GPSL1()
sat_state = SatelliteState(
    decoder = decoder,
    system = gpsl1,
    code_phase = code_phase,
    carrier_doppler = carrier_doppler,
    carrier_phase = carrier_phase,  # optional
)

Alternatively, pass a Tracking.SatState directly:

using Tracking
sat_state = SatelliteState(decoder, gpsl1, sat_state)

With at least 4 satellite states, compute the PVT solution:

pvt = calc_pvt(sat_states)
lla = get_LLA(pvt)  # latitude, longitude, altitude

Satellites from different constellations may be passed together. Because each GNSS references its broadcasts to its own system time, calc_pvt estimates one receiver clock bias per GNSS time system, so a combined fix needs at least 3 + M satellites for M distinct systems. The per-system clock offsets are reported as pvt.inter_system_biases relative to pvt.reference_system.