function Spdcf(options) {
  //>>includeStart('debug', pragmas.debug);
  Check.typeOf.number.greaterThan("options.A", options.A, 0.0);
  Check.typeOf.number.lessThanOrEquals("options.A", options.A, 1.0);
  Check.typeOf.number.greaterThanOrEquals("options.alpha", options.alpha, 0.0);
  Check.typeOf.number.lessThan("options.alpha", options.alpha, 1.0);
  Check.typeOf.number.greaterThanOrEquals("options.beta", options.beta, 0.0);
  Check.typeOf.number.lessThanOrEquals("options.beta", options.beta, 10.0);
  Check.typeOf.number.greaterThan("options.T", options.T, 0.0);
  //>>includeEnd('debug');

  this._A = options.A;
  this._alpha = options.alpha;
  this._beta = options.beta;
  this._T = options.T;
}
Variables for a Strictly Positive-Definite Correlation Function.

This reflects the `spdcf` definition of the
{@link https://nsgreg.nga.mil/csmwg.jsp|NGA_gpm_local} glTF extension.
Instances of this type are stored as the parameters within a
`CorrelationGroup`.

Parameters (A, alpha, beta, T) describe the correlation decrease
between points as a function of delta time:
```
spdcf(delta_t) = A_t * (alpha_t + ((1 - alpha_t)(1 + beta_t)) / (beta_t + e^(delta_t/T_t)))
```

@constructor
@param {Spdcf.ConstructorOptions} options An object describing initialization options
@experimental This feature is not final and is subject to change without Cesium's standard deprecation policy.