Keywords | File Formats

Calculation Scalar Format (*.csc)

A Calculation Scalar file is an ASCII text file formatted for compatibility with STK that ends in a .csc extension. Use the .csc file to add your own data into your STK scenario or read in additional data that comes from another system.

Keywords

Each calculation scalar file, regardless of the type of data in the file, contains some common elements called keywords. Keywords, and their associated values, must precede the actual data points.

Keywords used in Calculation Scalar files are NOT case-sensitive; the capitalization used in this document is for readability.

Keyword Required Description
stk.v.<major release number>.<minor release number> Yes

The version of STK software for which the file is formatted to be used.

  • Files can be created in, and imported to, STK software versions consistent with the file version stamp or higher.
  • The version stamp must be the first line in the calculation scalar file.
    Example:
      stk.v10.0

    A file created in and stamped with this version could be imported into STK software version 10.0 through the most recent version.
BEGIN Data
END Data 		Yes Sets off the beginning and end of the actual calculation scalar data. All other keyword phrases and data point specification (except the version stamp) will be inside these two keyword phrases. Refer to the sample file included in the File Format section for an example.
ReferenceEpoch No

The reference epoch time for the time values of the calculation scalar data in the file. Specify the reference epoch using Gregorian UTC time (dd mmm yyyy hh:mm:ss.s). There is no relationship between the reference epoch specified in the calculation scalar file and the actual scenario epoch in your STK scenario.

Default is the actual scenario epoch in the STK scenario.

Example:

    ReferenceEpoch 1 Jan 2003 00:00:00.0
In this case, a time of 5.5 for a particular attitude point would correspond to a time of 1 Jan 2003 00:00:05.5.
NumberOfIntervals Yes Number of intervals containing time-ordered tabulated scalar data. This entry must precede actual intervals.
BEGIN Interval
END Interval		 Yes Keywords identifying beginning and end of each interval.
NumberOfPoints Yes The number of time and value or time, value, and value rate entries within an interval. For example, if you enter NumberOfPoints 20, 20 TimeValues data lines or TimeValueRate data lines would be included. This entry must precede actual paired data.
BEGIN TimeValues
END TimeValues		 Yes Indicates that subsequent time-ordered tabulated data will contain two columns: time and scalar values.
BEGIN TimeValueRates
END TimeValueRates		 Yes Indicates that subsequent time-ordered tabulated data will contain three columns: time, scalar values, and their rates.
InterpolationMethod No

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

  • Lagrange (Default)
  • Hermite - Allows you to take advantage of angular velocity information, if available, in order to achieve smoother ephemeris interpolation. It may be especially useful when using tables containing very irregularly spaced data points or data representing spinning ephemeris that can be susceptible to ringing and aliasing effects if derivative information is not considered during interpolation. Hermitian interpolation assumes that the velocity component of the ephemeris is the derivative of the position. Hermitian interpolation should not be used when velocity data is not available as part of the ephemeris table.
  • HoldPrevious- Hold the value from the closest previous sample time.
  • HoldNext- Use the value of the next sample time that occurs after the current sample.
  • HoldNearest- Use the value from the sample time that is nearest to the requested time.

Default is Lagrange.

Examples:

InterpolationMethod    Lagrange
InterpolationMethod    Hermite
InterpolationOrder No

This keyword has been deprecated and replaced with InterpolationSamplesM1; it has the same format and function as its replacement.


Examples:
InterpolationOrder    1
InterpolationSamplesM1 No

One less than the number of points used in the interpolation. For the Lagrange interpolation method, this is also the interpolation order. For the Hermitian interpolation method, the interpolation order is:
(2 x InterpolationSamplesM1) + 1.

Default is 5.

Example:

If InterpolationMethod is Lagrange, the following setting will select linear interpolation:

InterpolationSamplesM1    1
TimeFormat No

Specifies a keyword defining the date format of time tags. If set, each line of data in the file begins with a time in the specific date format followed by the rest of the data. Spaces are valid whenever the format admits them (e.g., 1 Jan 2007 12:00:00.000), but quotes around the time strings are invalid.

For information on date format options, see DateTime Formats.
UnitType No

Unit type, e.g. Distance, Time, Angle, etc. (see Scenario Properties Units page for a list of unit types), which defines the type of tabulated scalar data in this file. If UnitType is omitted, it is assumed that data is unitless.
ValueUnit No

Defines the unit of the tabulated data in the file. The unit must be valid for the specified UnitType.

Requires corresponding units, including compound units, to be specified using abbreviations; for example, km and km/sec^2. The specified abbreviation string must be consistent with the UnitType. If ValueUnit is omitted, it is assumed that SI units appropriate for the specified UnitType are used.

Use only if the UnitType is specified.

The tabulated data must be entered as numeric values. Units that do not allow numeric values are invalid.

Example:

For UnitType Angle:
  • Valid ValueUnit: deg, rad, arcMin, etc.
  • Invalid UnitType: Deg:Min:Sec

For a list of valid abbreviations, go to Scenario-->Basic-->Units property page.
ValueRateUnit No

Defines the rate of the unit of the tabulated data in the file. The unit must be valid for the specified UnitType.

Requires corresponding units, including compound units, to be specified using abbreviations; for example, km and km/sec^2. The specified abbreviation string must be consistent with the UnitType. If ValueRateUnit is omitted, then it is assumed that the rates are computed using ValueUnit per second.

Use only if the UnitType is specified.

The tabulated data must be entered as numeric values. Units that do not allow numeric values are invalid.

Example:

For UnitType Distance, example ValueRateUnits are: ft, sec, and km/sec^2.

For a list of valid abbreviations, go to Scenario-->Basic-->Units property page.

DimensionName

(deprecated)

 No

This keyword has been deprecated and replaced with UnitType.

Dimension name, e.g. Distance, Time, Angle, etc. (see Scenario Properties Units page for a list of dimension names), which defines dimension of tabulated scalar data in this file. Scalar values must be in SI units of specified dimension. Scalar value rates must be in SI units of specified dimension per second. If omitted, tabulated scalar data is interpreted as Unitless.

DimensionUnit

(deprecated)

 No

This keyword has been deprecated and replaced with ValueUnit and ValueRateUnit.

Defines the unit of the tabulated data in the file. The unit must be valid for the specified DimensionName.

Use only if the DimensionName is specified.

The tabulated data must be entered as numeric values. Units that do not allow numeric values are invalid.

Example:

For DimensionName Angle:
  • Invalid DimensionUnit: Deg:Min:Sec
  • Valid DimensionUnits: Degrees, Radians, Arc Minutes, etc.
ComputeSampleRate No

Used with files that do not include Rates. Values include:

  • ForwardDifference - Use the next point and this point to compute the rate.
  • BackwardDifference - Use the previous point and this point to compute the rate.
  • CentralDifference - Use the previous point and the next point to compute the rate.

TimeValues and TimeValueRates are mutually exclusive so only one is required.

File Formats

While the sections above outline the basic format for a Calculation Scalar file, the section below outlines the format used to specify actual data points in the Calculation Scalar file.

  • TimeValues
  • TimeValueRates

    • The following conventions must be observed when specifying data points in any format:

    • Each line contains only one data point.
    • The values on each line must be separated by at least one space.
    • The lines must be listed in ascending order in time but do not have to be evenly spaced in time.
    • You cannot have multiple points at the same time.
    • There must be at least as many points as specified by the NumberOfPoints keyword.

TimeValues Format

Individual data points following the TimeValues keyword look like this:

<TimeInSeconds> <ScalarData>

where,

<TimeInSeconds> The time value of the point in seconds (in the format xxxx.xxx) relative to the epoch as defined by the ReferenceEpoch keyword.
<ScalarData> Scalar data in units specified by the DimensionName keyword.

TimeValueRates Format

Individual data points following the TimeValues keyword look like this:

<TimeInSeconds> <ScalarData> <TimeRateOfChange>

where,

<TimeInSeconds> The time value of the point in seconds (in the format xxxx.xxx) relative to the epoch as defined by the ReferenceEpoch keyword.
<ScalarData> Scalar data in units specified by the DimensionName keyword.
<TimeRateOfChange> The time rate of change of the corresponding value.

Calculation Scalar Sample Files

TimeValues sample file.

TimeValueRates sample file.