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LOGGING_FORMAT.md

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Raw

Logging

GnssLogger allows you to output raw data about GNSS/GPS to files so they can be visualized in the GNSS Analysis App.

Row prefixes

Each row of the file is prefixed with a string designating the data type:

If the device supports uncalibrated sensors (accelerometer, gyroscope, magnetometer) then those values are logged, otherwise the calibrated version of those sensors is logged (see SensorEvent.values() for differences between the two).

Header

The header of the CSV file explains the fields logged for each data type:

# Raw,utcTimeMillis,TimeNanos,LeapSecond,TimeUncertaintyNanos,FullBiasNanos,BiasNanos,BiasUncertaintyNanos,DriftNanosPerSecond,DriftUncertaintyNanosPerSecond,HardwareClockDiscontinuityCount,Svid,TimeOffsetNanos,State,ReceivedSvTimeNanos,ReceivedSvTimeUncertaintyNanos,Cn0DbHz,PseudorangeRateMetersPerSecond,PseudorangeRateUncertaintyMetersPerSecond,AccumulatedDeltaRangeState,AccumulatedDeltaRangeMeters,AccumulatedDeltaRangeUncertaintyMeters,CarrierFrequencyHz,CarrierCycles,CarrierPhase,CarrierPhaseUncertainty,MultipathIndicator,SnrInDb,ConstellationType,AgcDb,BasebandCn0DbHz,FullInterSignalBiasNanos,FullInterSignalBiasUncertaintyNanos,SatelliteInterSignalBiasNanos,SatelliteInterSignalBiasUncertaintyNanos,CodeType,ChipsetElapsedRealtimeNanos
# 
# UncalAccel,utcTimeMillis,elapsedRealtimeNanos,UncalAccelXMps2,UncalAccelYMps2,UncalAccelZMps2,BiasXMps2,BiasYMps2,BiasZMps2
# 
# Accel,utcTimeMillis,elapsedRealtimeNanos,AccelXMps2,AccelYMps2,AccelZMps2
# 
# UncalGyro,utcTimeMillis,elapsedRealtimeNanos,UncalGyroXRadPerSec,UncalGyroYRadPerSec,UncalGyroZRadPerSec,DriftXRadPerSec,DriftYRadPerSec,DriftZRadPerSec
# 
# Gyro,utcTimeMillis,elapsedRealtimeNanos,GyroXRadPerSec,GyroYRadPerSec,GyroZRadPerSec
# 
# UncalMag,utcTimeMillis,elapsedRealtimeNanos,UncalMagXMicroT,UncalMagYMicroT,UncalMagZMicroT,BiasXMicroT,BiasYMicroT,BiasZMicroT
# 
# Mag,utcTimeMillis,elapsedRealtimeNanos,MagXMicroT,MagYMicroT,MagZMicroT
# 
# OrientationDeg,utcTimeMillis,elapsedRealtimeNanos,yawDeg,rollDeg,pitchDeg
# 
# Fix,Provider,LatitudeDegrees,LongitudeDegrees,AltitudeMeters,SpeedMps,AccuracyMeters,BearingDegrees,UnixTimeMillis,SpeedAccuracyMps,BearingAccuracyDegrees,elapsedRealtimeNanos,VerticalAccuracyMeters,MockLocation
# 
# Nav,Svid,Type,Status,MessageId,Sub-messageId,Data(Bytes)
# 
# Status,UnixTimeMillis,SignalCount,SignalIndex,ConstellationType,Svid,CarrierFrequencyHz,Cn0DbHz,AzimuthDegrees,ElevationDegrees,UsedInFix,HasAlmanacData,HasEphemerisData,BasebandCn0DbHz
#
# Agc,utcTimeMillis,TimeNanos,LeapSecond,TimeUncertaintyNanos,FullBiasNanos,BiasNanos,BiasUncertaintyNanos,DriftNanosPerSecond,DriftUncertaintyNanosPerSecond,HardwareClockDiscontinuityCount,AgcDb,CarrierFrequencyHz,ConstellationType

Note that on devices that shipped with Android T and higher, Automatic Gain Control is logged to its own records starting with Agc - the AgcDb field that is part of the Raw message will be empty.

Sample data

Sample data looks like:

Fix,GPS,28.1435263000,-82.2971356000,-14.200000762939453,0.09635656,5.857,108.336426,1663712656000,,,445420306913617,11.185,0
Status,1663712658000,18,0,1,1,,12.80,285.0,16.0,1,1,0,
Status,1663712658000,18,1,1,3,,19.00,320.0,14.0,1,1,0,
Raw,1663707711608,32083712000000,18,,-1347710845896978382,0.800237774848938,15000247.00164795,-27.699302103483184,39.875882248753776,31,10,0.0,1,79120,53,29.6,102.51119995117188,2.240000009536743,16,0.0,0.0,1575420030,,,,0,,1,1.11,24.6,0.0,0.0,,,C,30663387810588
Raw,1663707711608,32083712000000,18,,-1347710845896978382,0.800237774848938,15000247.00164795,-27.699302103483184,39.875882248753776,31,21,0.0,35,14,35,32.6,-175.76475524902344,0.8314999938011169,16,0.0,0.0,1575420030,,,,0,,1,1.11,27.6,0.0,0.0,,,C,30663387810588
UncalMag,1663164669191,65972055195160,221.51251,89.793755,-21.16875,213.84875,180.1958,5.4516187
UncalGyro,1663164669189,65972053803181,0.0006108648,-0.020769402,0.023518294,-0.009432952,0.000007726701,-0.008078051
UncalAccel,1663164669190,65972054923181,0.4642076,7.7742805,5.8707905,0.0,0.0,0.0
OrientationDeg,1663164669209,65972073175160,201.0,-5.0,-52.0
Nav,3,769,1,-1,14,116,5,-126,11,42,-69,104,85,-17,63,-96
Nav,30,1281,1,12,5,75,-83,-64,-34,75,-83,-64,-34,75,-83,-64,-34,-64,44,-61,-11,-45,-60,53,-23,-48,14,104,-30,-30,-128,-21,-67,-68,-101,-55,6,-59,80,3,-107,-80,-7,10,35
Agc,1675109588736,4105000000,,,-1359144802631003092,0.0,2200000588,,,52,19.718292236328125,1176450000,1
Agc,1675109588736,4105000000,,,-1359144802631003092,0.0,2200000588,,,52,49.79810333251953,1602000000,3

Field definitions

A description of the different logged fields can be found below.

Raw - The raw GNSS measurements of one GNSS signal (each satellite may have 1-2 signals for L5-enabled smartphones), collected from the Android API GnssMeasurement:

  • utcTimeMillis - Milliseconds since UTC epoch (1970/1/1), converted from GnssClock
  • TimeNanos - The GNSS receiver internal hardware clock value in nanoseconds.
  • LeapSecond - The leap second associated with the clock's time.
  • TimeUncertaintyNanos - The clock's time uncertainty (1-sigma) in nanoseconds.
  • FullBiasNanos - The difference between hardware clock getTimeNanos() inside GPS receiver and the true GPS time since 0000Z, January 6, 1980, in nanoseconds.
  • BiasNanos - The clock's sub-nanosecond bias.
  • BiasUncertaintyNanos - The clock's bias uncertainty (1-sigma) in nanoseconds.
  • DriftNanosPerSecond - The clock's drift in nanoseconds per second.
  • DriftUncertaintyNanosPerSecond - The clock's drift uncertainty (1-sigma) in nanoseconds per second.
  • HardwareClockDiscontinuityCount - Count of hardware clock discontinuities.
  • Svid - The satellite ID. More info can be found here.
  • TimeOffsetNanos - The time offset at which the measurement was taken in nanoseconds.
  • State - Integer signifying sync state of the satellite. Each bit in the integer attributes to a particular state information of the measurement.
  • ReceivedSvTimeNanos - The received GNSS satellite time, at the measurement time, in nanoseconds.
  • ReceivedSvTimeUncertaintyNanos - The error estimate (1-sigma) for the received GNSS time, in nanoseconds.
  • Cn0DbHz - The carrier-to-noise density in dB-Hz.
  • PseudorangeRateMetersPerSecond - The pseudorange rate at the timestamp in m/s.
  • PseudorangeRateUncertaintyMetersPerSecond - The pseudorange's rate uncertainty (1-sigma) in m/s.
  • AccumulatedDeltaRangeState - This indicates the state of the 'Accumulated Delta Range' measurement. Each bit in the integer attributes to state of the measurement.
  • AccumulatedDeltaRangeMeters - The accumulated delta range since the last channel reset, in meters.
  • AccumulatedDeltaRangeUncertaintyMeters - The accumulated delta range's uncertainty (1-sigma) in meters.
  • CarrierFrequencyHz - The carrier frequency of the tracked signal.
  • CarrierCycles - The number of full carrier cycles between the satellite and the receiver.
  • CarrierPhase - The RF phase detected by the receiver.
  • CarrierPhaseUncertainty - The carrier-phase's uncertainty (1-sigma).
  • MultipathIndicator - A value indicating the 'multipath' state of the event.
  • SnrInDb - The (post-correlation & integration) Signal-to-Noise ratio (SNR) in dB.
  • ConstellationType - GNSS constellation type. The value is one of those constants with CONSTELLATION_ prefix in GnssStatus.
  • AgcDb (deprecated) - The Automatic Gain Control level in dB. On devices that shipped with Android T and higher, Automatic Gain Control is logged to its own records starting with Agc - this AgcDb field that is part of the Raw message will be empty.
  • BasebandCn0DbHz - The baseband carrier-to-noise density in dB-Hz. Only available in Android 11 and higher.
  • FullInterSignalBiasNanos - The GNSS measurement's inter-signal bias in nanoseconds with sub-nanosecond accuracy. Only available in Android 11 and higher.
  • FullInterSignalBiasUncertaintyNanos - The GNSS measurement's inter-signal bias uncertainty (1 sigma) in nanoseconds with sub-nanosecond accuracy. Only available in Android 11 and higher.
  • SatelliteInterSignalBiasNanos - The GNSS measurement's satellite inter-signal bias in nanoseconds with sub-nanosecond accuracy. Only available in Android 11 and higher.
  • SatelliteInterSignalBiasUncertaintyNanos - The GNSS measurement's satellite inter-signal bias uncertainty (1 sigma) in nanoseconds with sub-nanosecond accuracy. Only available in Android 11 and higher.
  • CodeType - The GNSS measurement's code type.
  • ChipsetElapsedRealtimeNanos - The elapsed real-time of this clock since system boot, in nanoseconds.

Status - The status of a GNSS signal, as collected from the Android API GnssStatus.

  • UnixTimeMillis - Milliseconds since UTC epoch (1970/1/1), recorded from the most recent location update from the GPS_PROVIDER. If no GPS_PROVIDER location has been acquired yet this field will be empty. If the GPS_PROVIDER loses a fix (i.e., there is no location update within two seconds of a given Status epoch), this field will also be empty.
  • SignalCount - The total number of satellites in the satellite list.
  • SignalIndex - The index of current signal.
  • ConstellationType: The constellation type of the satellite at the specified index. The value is one of those constants with CONSTELLATION_ prefix in GnssStatus.
  • Svid: The satellite ID. More info can be found here.
  • CarrierFrequencyHz: The carrier frequency of the signal tracked.
  • Cn0DbHz: The carrier-to-noise density at the antenna of the satellite at the specified index in dB-Hz.
  • AzimuthDegrees: The azimuth the satellite at the specified index.
  • ElevationDegrees: The elevation of the satellite at the specified index.
  • UsedInFix: Whether the satellite at the specified index was used in the calculation of the most recent position fix (0 or 1).
  • HasAlmanacData: Whether the satellite at the specified index has almanac data (0 or 1).
  • HasEphemerisData: Whether the satellite at the specified index has ephemeris data (0 or 1).
  • BasebandCn0DbHz: The baseband carrier-to-noise density of the satellite at the specified index in dB-Hz. Only available in Android 11 and higher.

UncalAccel - Readings from the uncalibrated accelerometer, as collected from the Android API Sensor.TYPE_ACCELEROMETER_UNCALIBRATED:

  • utcTimeMillis - The sum of elapsedRealtimeNanos below and the estimated device boot time at UTC, after a recent NTP (Network Time Protocol) sync.
  • elapsedRealtimeNanos - The time in nanoseconds at which the event happened.
  • UncalAccel[X/Y/Z]Mps2 - [x/y/z]_uncalib without bias compensation.
  • Bias[X/Y/Z]Mps2 - Estimated [x/y/z]_bias.

UncalGyro - Readings from the uncalibrated gyroscope, as collected from the Android API Sensor.TYPE_GYROSCOPE_UNCALIBRATED:

  • utcTimeMillis - The sum of elapsedRealtimeNanos below and the estimated device boot time at UTC, after a recent NTP (Network Time Protocol) sync.
  • elapsedRealtimeNanos - The time in nanoseconds at which the event happened.
  • UncalGyro[X/Y/Z]RadPerSec - Angular speed (w/o drift compensation) around the [X/Y/Z] axis in rad/s.
  • Drift[X/Y/Z]RadPerSec - Estimated drift around [X/Y/Z] axis in rad/s.

UncalMag - Readings from the uncalibrated magnetometer as collected from the Android API Sensor.STRING_TYPE_MAGNETIC_FIELD_UNCALIBRATED:

  • utcTimeMillis - The sum of elapsedRealtimeNanos below and the estimated device boot time at UTC, after a recent NTP (Network Time Protocol) sync.
  • elapsedRealtimeNanos - The time in nanoseconds at which the event happened.
  • UncalMag[X/Y/Z]MicroT - [x/y/z]_uncalib without bias compensation.
  • Bias[X/Y/Z]MicroT - Estimated [x/y/z]_bias.

OrientationDeg - Each row represents an estimated device orientation, collected from Android API SensorManager.getOrientation():

  • utcTimeMillis - The sum of elapsedRealtimeNanos below and the estimated device boot time at UTC, after a recent NTP (Network Time Protocol) sync.
  • elapsedRealtimeNanos - The time in nanoseconds at which the event happened.
  • yawDeg - If the screen is in portrait orientation, this value equals the Azimuth degree (modulus to 0° and 360°). If the screen is in landscape orientation, it equals the sum (modulus to 0° and 360°) of the screen rotation angle (either 90° or 270°) and the Azimuth degree. Azimuth, refers to the angle of rotation about the -z axis. This value represents the angle between the device's y axis and the magnetic north pole.
  • rollDeg - Roll, angle of rotation about the y axis. This value represents the angle between a plane perpendicular to the device's screen and a plane perpendicular to the ground.
  • pitchDeg - Pitch, angle of rotation about the x axis. This value represents the angle between a plane parallel to the device's screen and a plane parallel to the ground.

Fix - Each row represents a Location, collected from the Location API (for GPS from the GPS_PROVIDER and NLP from the NETWORK_PROVIDER) and Fused Location API (for FLP from the FUSED_PROVIDER).

Agc - Each row represents a combination of the GnssClock and GnssAutomaticGainControl that are reported as part of a GnssMeasurementEvent. Note that there will be multiple AGC records (one per carrier frequency per constellation type - i.e., all satellites of the same constellation and same frequency have the same AGC), reported in GnssMeasurementsEvent.getGnssAutomaticGainControls(), for each clock/event.

References