Restart

To provide for situations in which a filter or simulator run may be interrupted, the restart options in the following table are available.

NOTE: See also the page on Process Control regarding the effect of different settings for the MeasurementProcessingMode attribute on the filter's processing of measurements at or near the restart time.

Restart Options
Option Description
SaveRecordsToFile If set to true (the default), the restart records will be written to the restart file.

If false, the restart file will:
  • not be created if in Initial mode, or
  • not be modified if in Restart or Autorestart mode.
MaxRecordsInFile Enter an integer specifying the maximum number of restart points to be included in the restart time list.
SaveFrequency Enter a time value specifying the interval between restart points in the restart time list.

Note: Restart filenames are now unique for restart times at .001 second intervals. Attempting to create restart files for times less than .001 seconds apart will result in overwriting of restart files.

BackupRestartRecords When set to false the restart directory will not be copied when starting or restarting a filter or simulator.
StochasticModelUpdates Set the Source attribute to "Explicit" to display the GaussMarkovList, RandomWalkList, and VasicekList attributes. These lists may be updated to provide changes to the stochastic definitions of estimated parameters or their nominal values. Set the Source attribute to ObjectSettings to have the restart operation detect and apply updated stochastic model definitions directly from object settings.

Note: This flag does not apply to the Vasicek model long term mean uncertainty controls "Error Threshold" and "PNStep" since these controls do not cause a state reset (i.e. drop/add) when modified. These controls are updated on Restart whenever they are changed in the Object Settings regardless of the setting of this flag.

ClockUpdates Set the Enabled attribute to true to display the ClockList attribute.
OnStateSizeChange.
StateReductionMethod
(Filter only)
SimpleTruncation - The covariance of the reduced state is simply the extracted covariance of the state on the Restart file.
SatelliteMassUpdates Set the Enabled attribute to true to display the SatelliteMassList attribute.

Warning: If you make an unusually large change in mass, you must manually adjust SRP and drag coefficients; failure to make a consistent change can lead to degraded results.

OnStateSizeChange.
IfCovGoesNegative
(Filter only)

Action options are:

  • Prompt User (default) - displays a message box that prompts the user either to abort the run or to continue after applying diagonal deweighting.
  • Abort - causes the run to abort without prompting.
  • ApplyDiagonalDeweighting - applies the deweighting without prompting.

Use the PercentSigmaDeweighting attribute to enter the percentage diagonal weighting to be applied.

ResetGNSSUTCSteering When set to true, will reset at the Restart time, the "GNSS UTC" time steering bias and/or drift and/or controls to the values specified in the GNSSConstellation.GNSSUTCTimeSteering list.

NOTE: When you save a scenario with the StartMode set to AutoRestart and later load that scenario, it will automatically select the last restart point available. This way you can load a scenario, click the play button and pick up exactly where you left off without having to choose a restart time.

ConstantBiasResetList

The ConstantBiasResetList property specifies a list of stochastic model state parameters for which the user would like to reset the associated constant bias term without updating the associated state error covariance. Any parameter modeled using the single parameter GaussMarkov model, the Random Walk model, or Vasicek model is a choice for this list.

Click to the right of the ConstantBiasResetList attribute to display a List dialog that enables you to add and remove any or all of the state parameters that are listed. Candidate state parameters are described in the GausMarkovList, RandomWalkList, and VasicekList given below. The state parameter entry is a string of the form <ObjectName>.<StateName> where the <ObjectName> choices are described below by the GaussMarkovList.ObjectName entry and the <StateName> choices are described by the GaussMarkovList.StatetName entry. Example ConstantBiasResetList entries are TrackingSystem1.Facility1.Range, Satellite1.BallisticCoefficient.B, Satellite1.SolarPressure.Cp, and Satellite1.Transponder1.TransponerBias.

For the parameters in the list the associated constant bias value will be reset by zeroing the current filter state error estimate and adding the error into the constant value. Unlike modifying the constant bias using the GaussMarkov, Random Walk, or Vasicek lists below, the filter state will not be "re-initialized" using a state drop/add procedure. Note however that the FIS smoother and VLS state change processing is unchanged. Also note that for the Vasicek parameter it is the bias error estimate in the "long term state that is set to zero, with the "short term" error estimate adjusted accordingly.

GaussMarkovList

This is a fixed list. Each row contains data for a Restart File Gauss Markov state. The Gauss Markov states include the force model state parameters for Satellite Ballistic Coefficient, Satellite Atmospheric Density, and Satellite Solar Pressure. Finite Maneuver states are currently not included. The list also includes measurement modeling parameters, i.e. Transponder Biases, Facility Measurement Biases, Satellite Measurement Biases, and RetroreflectorDelays that are modeled as Gauss Markov sequences. The list contains some informational only (i.e. read-only) attributes, and some attributes which may be modified. Included are:

NOTE: In version 6.1, the StateName for the spherical SRP model changed from "Scale" to "Cp".

GaussMarkovList Attributes
Attribute Read Only? Description
ObjectName yes State object name, e.g. Satellite1, Satellite1.Transponder, Facility1, etc.
StateName yes State descriptor = AtmosphericDensity | BallisticCoefficient.B | SolarPressure.Cp | SolarPressure2.Scale | SolarPressure2.Y Bias | TransponderBias | Range | Doppler | Azimuth | Elevation | TroposphereBias etc.
BiasUnits yes Displayed units for the Gauss Markov bias parameters. See below.
ConstantBias no Constant (or "nominal") bias.
StateBiasError yes Current state bias error estimate.
TotalBias yes Current bias estimate = ConstantBias + StateBiasError.
StateBiasErrorSigma yes Current state bias estimate error root-variance.
BiasSigma no Gauss Markov Bias Sigma (i.e. the uncertainty in the nominal bias).
HalfLife no State Bias error half life in time units.

RandomWalkList

This is a fixed list. Each row contains data for a Restart File RandomWalk state. The RandomWalk states includes measurement modeling parameters, i.e. Transponder Biases, Facility Measurement Biases, Satellite Measurement Biases, and RetroreflectorDelays that are modeled as RandomWalk stochastic sequences . The list contains some informational only (i.e. read-only) attributes, and some attributes which may be modified. Included are:

RandomWalkList Attributes
Attribute Read Only? Description
ObjectName yes State object name, e.g. Satellite1, Satellite1.Transponder, Facility1, etc.
StateName yes State descriptor
BiasUnits yes Displayed units for the Gauss Markov bias parameters. See below.
ConstantBias no Constant (or "nominal") bias.
StateBiasError yes Current state bias error estimate.
TotalBias yes Current bias estimate = ConstantBias + StateBiasError.
StateBiasErrorSigma yes Current state bias estimate error root-variance.
InitialBiasSigma no Initial Bias Sigma (i.e. the uncertainty in the constant bias).
DiffusionCoefficient no Determines the amount of process noise to be added to the state covariance during time updates.

VasicekList

This is a fixed list. Each row contains data for a Restart File Vasicek state. The Vasicek states includes measurement modeling parameters, i.e. Transponder Biases, Facility Measurement Biases, Satellite Measurement Biases, and RetroreflectorDelays that are modeled as Vasicek stochastic sequences . The list contains some informational only (i.e. read-only) attributes, and some attributes which may be modified. Included are:

VasicekList Attributes
Attribute Read Only? Description
ObjectName yes State object name, e.g. Satellite1, Satellite1.Transponder, Facility1, etc.
StateName yes State descriptor
BiasUnits yes Displayed units for the Vasicek bias parameters. See below.
ConstantBias no Constant (or "nominal") bias.
StateBiasError yes Current state bias error estimate.
TotalBias yes Current bias estimate = ConstantBias + StateBiasError.
StateBiasErrorSigma yes Current state error root-variance associated with the "TotalBias" estimate.
HalfLife no Vasicek (Short Term) Bias Sigma HalfLife
StateLongTermMeanError yes Current state error estimate of the long term mean, i.e. this is the current error estimate of "ConstantBias"
StateLongTermMeanErrorSigma yes Current state error root-variance associated with "StateLongTermMeanError"
LongTermMeanErrorSigma no Vasicek model Long Term Sigma (i.e. the inital error estimate of "ConstantBias").

Please note the following:

  1. The values displayed correspond to the Restart record currently displayed. If the Restart record changes then the list changes. Only the last list displayed gets applied.
  2. The lists are not applied to the Restart file until the Go action is selected (and the Filter or Simulator reaches the point were the Restart file is processed).
  3. After each list is applied, the list is cleared and the Restart.StochasticModelUpdates.Enabled flag is reset to false.
  4. For the GaussMarkovList, changing either the ConstantBias, BiasSigma or HalfLife will reinitialize that Filter or Simulator state, i.e. the state bias error estimate will be set to zero, the state bias estimate error variance will be set to BiasSigma2, and the cross-correlations between this state and the other states will be set to zero. This is effectively a Filter or Simulator state deletion/addition: deleting the existing state, and then adding a new state. The is similarly true for the RandomWalkList and the VasicekList.
  5. Changing the ConstantBias, BiasSigma or HalfLife for one state in a n-state model will reinitialize all n-states in the Filter or Simulator (e.g. changing SolarPressure2.Scale will reinitialize both SolarPressure2.Scale and SolarPressure2.YBias).
  6. To change the Stochastic Model Type (e.g. change from GaussMarkov to Vasicek) the user must change the model type in the "original" object properties. Example, to change the range bias model type for a facility, change the range bias model type in that facility's MeasurementStatistics List and update the parameters for that model accordingly. This change will be treated as a state deletion/addition.

Also Note: If you change the stochastic model parameters or the Constant value of a state variable in the GaussMarkovList, RandomWalkList, or VasicekList during Restart, then the corresponding object properties (e.g. tracker MeasurementStatistics, satellite ForceModel parameters, transponder bias) are also changed to match the Restart state values. You must save the scenario to preserve the object properties settings and restart file settings; failure to do so will result in modeling errors in subsequent runs.

Bias Units

Users should remember to convert biases into the required units before attempting to modify the GaussMarkovList. The required units are:

ClockList

This is a fixed list. Each row contains data for a Restart File Clock state, where the state can consist of {phase, frequency} or {phase, frequency, aging}. The Clock state data includes the current state estimates and state estimate error root-variances, as well as clock process noise parameters. The list contains some informational only (i.e. read-only) attributes, and some attributes that can be modified. Included are:

ClockList Attributes
Attribute Read Only? Description
ObjectName yes Full name of the GNSS Receiver or GNSS Satellite Object associated with this clock state, e.g. TrackingSystem1.Facility1.GNSSReceiver1, Satellite1.GNSSReceiver1, GNSS.PRN01 etc.
PhaseEstimate no Clock phase error estimate.
FreqEstimate no Clock frequency error estimate.
AgingEstimate no Clock aging estimate.
PhaseSigma yes Clock phase estimate error root-variance.
FreqSigma yes Clock frequency estimate error root-variance.
AgingSigma yes Clock aging estimate error root-variance.
A0 yes Frequency-modulated (FM) clock white noise statistic.
Aminus1 yes FM clock flicker noise statistic (not currently modeled).
Aminus2 yes FM clock random walk statistic.
AgingWN yes FM clock drift statistic.

Please note the following:

  1. The values displayed correspond to the Restart record currently displayed. If the Restart record changes then the list changes. Only the last list displayed gets applied.
  2. The list is not applied to the Restart file until the Go action is selected (and the Filter or Simulator reaches the point were the Restart file is processed).
  3. After the list is applied, the list is cleared and the Restart.ClockUpdates.Enabled flag is reset to false.
  4. Changing either the phase, frequency, or aging state estimate or state sigma will reinitialize the states for that Filter or Simulator clock, i.e. the state estimates and sigmas estimate will be set to the input values given in the ClockList, and the cross-correlations between these states and the other states will be set to zero. This is effectively a Filter or Simulator state deletion/addition: deleting the existing clock states, and then adding a new state.
  5. The ClockList cannot be used to add or delete "aging" as part of the clock state. (That is, if "aging" is not a clock state then the AgingSigma will be 0 and the user cannot change the AgingSigma to a non-zero value in an effort to add "aging". Likewise if "aging" is a clock state the user cannot set the AgingSigma to 0 in an effort to delete "aging".).
  6. Changing the process noise parameters (A0, Aminus1, Aminus2, or AgingWN) will not reinitialize the clock.

Also Note: If you change any of the process noise parameters (A0, Aminus1, Aminus2, or AgingWN) in the ClockList during Restart, then the corresponding object properties (i.e. GNSS Receiver or GNSS Satellite clock process noise parameters) are also changed to match the Restart state values. You must save the scenario to preserve the object properties settings and restart file settings; failure to do so will result in modeling errors in subsequent runs.

SatelliteMassList

This is a fixed list. Each row contains data for each satellite in the Restart file. Data displayed include satellite identification data as well as the current mass estimate. The list contains some informational only (i.e. read-only) attributes, and some attributes that can be modified. Included are:

SatelliteMassList Attributes
Attribute Read-only? Description
SatelliteName yes Name of the satellite
SatelliteID yes Satellite tracking ID
Mass no Current Mass estimate on the Restart file

Please note the following:

  1. The displayed values correspond to the Restart record currently displayed. If the Restart record changes, then the list changes. Only the last list displayed is applied.
  2. The list is not applied to the Restart file until the Go action is selected (and the Filter or Simulator reaches the point where the Restart file is processed).
  3. After the list is applied, the list is cleared and the Restart.SCMassUpdates.Enabled flag is reset to false.
  4. Changing the mass will NOT change the current estimates for states related to the mass such as drag and solar pressure. If the user makes an unusually large change in mass then the user must manually adjust SRP and drag coefficients, and failure to make a consistent change can lead to degraded results.
  5. Changing the mass value will NOT change the initial mass setting in the Satellite object properties.

ODTK 6.5