Advanced Data for Components in Analysis Workbench

Click Advanced Options... on the Add Calculation Component page to set parameters related to Save Options, Time Limits, Sampling, Interpolation, Convergence and Integral for STK's Analysis Workbench capability.

Save Options

Time limits for computing integral data and save options can be either controlled by the application preferences that are found under Analysis Workbench category or by the settings specified locally on this Advanced Data page.

Option Description
Use Application Preferences Uses the application level settings for the selected Analysis Workbench component.
Save Computed Data

Overrides the application level setting and saves derived data for the selected Analysis Workbench component. It may be beneficial to save and reload derived data instead of performing expensive time-consuming computations.

There is an option to always save computed data so as to avoid re-computing it on load; and there is an option to explicitly specify interval or interval list as time limit for integration.

Time Limits

Option Description
Use Application Preferences

The visibility algorithm first takes samples then sub-samples to determine visibility intervals to within the specified tolerances. Use this option unless you are satisfied with the resolution using a fixed-time step. Although the Find Precise Event Times option takes more time for the same sampling step size as the Use Samples Only option, this option is good for larger time steps to achieve acceptable answers.

Time Limits If you choose this option, the visibility intervals are determined based on the taken samples (in other words, visibility starts at the first sample time where visibility is achieved).

Sampling

Select one of the following sampling types and define its parameters:

Fixed Step

This method forces the sampling performed by the access algorithm to run at a fixed step. This outcome is desirable for cases where no sudden changes exist in the motion or behavior of objects involved in the coverage analysis and where the ephemeris of moving objects is stored at a fixed step size. Under these conditions combined with the Use Light Time Delay option off (not selected) and with the start time of the coverage analysis coincident with the start of the stored ephemeris, ephemeris interpolation can be avoided during the access sampling phase.

Ephemeris interpolation would still be performed during sub-sampling if Find Precise Event Times is turned on (selected).

Option Description
Step Size Specifies the fixed step size for the fixed step control.

Relative Tolerance

This method allows the access algorithm to determine the sampling step size based on the constraints being processed. It is typically the safest mode to run in, especially when the motion of the assets is complex. However, this method does require some additional computation time to determine the next step size. If the conditions of the scenario are known to be slowly changing, the Max step size can be increased to improve the performance of the coverage computations.

Option Description
Minimum Time Step The minimum step size that is allowed to be taken.
Maximum Time Step

The maximum step size that is allowed to be taken.

Step at Boundaries Specifies the initial step taken at boundary times that have been identified as times when behavior of the sampled function changes abruptly. This is done to reset sampling at these times to smaller steps regardless of the past behavior in order to ensure that abrupt changes are detected and appropriately sampled.
Relative Tolerance

Specifies the allowable relative tolerance for errors between the actual samples and those predicted based on linear extrapolation.
Absolute Tolerance

Specifies the allowable absolute tolerance for errors between the actual samples and those predicted based on linear extrapolation.

Curvature Tolerance

Option Description
Minimum Time Step The minimum step size that is allowed to be taken.
Maximum Time Step

The maximum step size that is allowed to be taken.

Step at Boundaries Specifies the initial step taken at boundary times that have been identified as times when behavior of the sampled function changes abruptly. This is done to reset sampling at these times to smaller steps regardless of the past behavior in order to ensure that abrupt changes are detected and appropriately sampled.
Relative Tolerance

Specifies the allowable relative tolerance for errors between the actual samples and those predicted based on linear extrapolation.
Absolute Tolerance

Specifies the allowable absolute tolerance for errors between the actual samples and those predicted based on linear extrapolation.
Curvature Tolerance Specifies the allowable curvature tolerance for differences between slopes evaluated at consecutive samples.

Interpolation

Option Description
Type

The method by which STK interpolates between vector points. Valid values are:

  • Lagrange - Lagrange interpolation method of specified order that only samples of the function.
  • Hermite - Hermite interpolation method of the specified order that uses both samples of the function and their rates.
Order

The interpolation order to be used. By default, STK uses 1st order interpolation. Override the default by specifying a different interpolation order.

Integral

Option Description
Type

The Integral type to be used:

  • Adaptive Lobatto - adaptive Lobatto quadrature method that may sub-sample the function if necessary to satisfy the specified relative Tolerance. The method stops sub-sampling after the specified Maximum Iterations number.
  • Simpson - Simpson quadrature method.
  • Trapezoidal - trapezoidal quadrature method.

During the times when the integrand is not available, the integral can be either also made unavailable or it can be kept constant by selecting Keep integral constant outside of time limits.

Convergence

Option Description
Sense Specifies preference for the values returned at the crossing times with respect to the condition satisfaction threshold. Simple means that the times returned within tolerance can correspond to condition values on either side of the threshold. From Above means that the times returned within tolerance must correspond to condition values on or above the threshold. From Below means that the times returned within tolerance must correspond to condition values on or below the threshold.
Absolute Tolerance

Specifies the allowable tolerance for absolute difference in sampled condition values when determining the crossing of the condition satisfaction threshold.
Relative Tolerance

Specifies the allowable tolerance for relative difference in sampled condition values when determining the crossing of the condition satisfaction threshold.
Time Tolerance Specifies the allowable tolerance in finding the exact time of extremum or threshold crossing.