Measuring Age Of Data

Age Of Data measures the time between the end of a coverage interval and the current time. The dynamic definition of Age Of Data is the time since the most recent prior coverage interval ended; it is defined as 0 if the point is currently covered, and as 1000000 seconds if the animation time is prior to the first access period. Options for the static definition of Age Of Data are described in the following table. Since Age Of Data and Response Time both measure time until the boundary of a coverage interval (though in opposite directions), the statistical values of the two measures over the coverage analysis interval are the same.

Compute options for Age Of Data

Option	Description
Average	The average response time over the entire coverage interval. Computed as:
Maximum	The maximum age of data over the entire coverage interval. Useful in determining the length of the longest gap between coverages.
Minimum	The minimum age of data over the entire coverage interval. Value is 0 if any accesses exist for the grid point.
Percent Below	The value computed indicates that the point has an age of data of at most R, X percent of the time, where R is the computed value and X is the Percent Level you specify.
Percent Below Gaps Only	The computed value indicates that the point has an age of data of at most R, X percent of the time when in a coverage gap, where R is the computed value and X is a Percent Level that you specify.

STK Coverage uses an "optimistic" algorithm when coverage gaps that share a boundary with the coverage interval exist. The span of the coverage gap is measured using the coverage interval bound. This is important for the correct interpretation of the Age Of Data, Revisit Time, Time Average Gap and Response Time figures of merit.

Min # Assets

Use this field to specify the minimum number of Assets required for Coverage.

Displaying Response Time in a Graphics Window

Graphics are used to represent the static and dynamic value of Age Of Data. Graphics representing the dynamic values are only displayed during animation. If Satisfaction is enabled, the graphics follow the general behavior for satisfaction graphics. If Satisfaction is disabled, the graphics appear as described in the following table:

Static or Animation?	Grid points highlighted if they...
Static	are in a coverage gap at least once during the coverage interval
Animation	are currently in a coverage gap

The Satisfaction Threshold value is the time between the end of the most recent prior coverage interval and the current time. The default behavior for this figure of merit corresponds to a Satisfaction setting of Greater Than 0.