STK COVERAGE
Coverage analyzes
when and how well
regions on or above
the central body’s
surface are “covered”
by a collectionof assets basedon a user-defined
performance criteria.
Coverage uses the following variables todetermine the quality of system performancefor a chosen analysis interval:•	Coverage definition grid. The setof points used for sampling within
the area(s) of interest is called thecoverage grid. Coverage computes
FOM satisfaction based on the access
accessibility to these points.
•	
Coverage assets. The selection of vehicles,
sensors, or ground stations that define yourcoverage analysis system.
•	
Figure of merit (FOM). The quality
or type of coverage that measuressystem performance.
Coverage computes FOM satisfaction basedon the access from the coverage assets toeach of the coverage definition grid points.
In addition to reports and graphs, thesystem performance for any FOM is visuallydisplayed as color-coded performanceareas that can be displayed as cumulative
results over the analysis period or dynamic
instantaneous results at each time step.

Coverage definition
A coverage definition, which is also called anarea of interest, can be defined as:•	A contiguous area such as a country,
the globe, or a user-defined boundary•	A collection of areas – such as twostates and a lake
Pre-defined grid definitions. Global, latitude
bounds, lat/lon bounds, user-selected region,user-defined boundary, latitude line, andlongitude line

Point granularity (sampling). Grid definitions
are point sampled based on a specified
granularity or imported from a file that
customizes the location of the point sample

Coverage time. Measures the amountof time during which grid points arecovered, either in total time, time perday, or as a percentage.

Point altitude options. The coverage
grid can be located on the surface of theellipsoid or defined as follows: Altitude above
MSL, altitude above terrain, altitude above
WGS84, depth below MSL, altitude above
ellipsoid, depth below ellipsoid, and radius.

Revisit time. Measures the durationof intervals during which coverage
is not provided.

Grid constraints. Reference constraintclass, use object instance, use actual
objects on the grid points, and lineof sight obstruction surface.

Customize assets
Any vehicle, sensor, facility, chain orconstellation may be an asset with constraints
used in access determination. STK objects
may be used as assets in any combination.

Figures of Merit (FOM)
A set of pre-defined metrics to measure yourcoverage performance.
Simple coverage. Measures a point
is covered.
N asset coverage. Measures thenumber of assets available
simultaneously during coverage.

Access duration. Measures the duration ofindividual coverage intervals.
Number of accesses. Measures the numberof independent accesses of points.
Number of gaps. Measures the number ofgaps in coverage of points.
Access separation. Measures if a point has
coverage from multiple assets within a userdefined time tolerance.
Time average gap. Measures the average
length of the coverage gap found if
sampled randomly.
Response time. Measures the time
between a request for coverage at thepoint and the time at which the coverage isachieved. Options are mean, min/max, ornth-percentile values.
Access constraint. Measures the value ofa user-selected visibility constraint such aselevation angle or slant range, or probabilityof detection using TIREM.

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Dilution of precision. Measures therelative level of uncertainty of a navigation
solution due to the relative geometry of
the transmitter locations (i.e., Geometric,Position, Horizontal, Vertical, and Time).
Navigation accuracy. Measures theuncertainty of a navigation solution based on
one-way range measurements from a set oftransmitters. Most often, the transmitters arethose onboard GPS satellites.
System response time. Measures theelapsed time from a request for coverage
until collection assets are commanded,
the collection occurs and the downlink ofcollected data is complete.
Age of data. Measures the time since theend of the last coverage interval.
Cumulative N asset. Determines thenumber of unique assets providing
coverage to grid points.
Scalar calculation. Creates a FOM using theCalculation tool.

Coverage satisfaction
Satisfaction is a comparison operator
which establishes “if” or “when” a FOM is“satisfied.” The Satisfaction criteria identify
the relationship between the FOM value
and the user-specified threshold value (i.e.,
at least, equal to, at most, greater than,less than). This lets you quickly answer
questions of coverage.

Attitude Coverage
Attitude Coverage combines features ofAttitude and Coverage to enable you toanalyze coverage in various directions overtime, using several attitude-dependent
figures of merit.

Coverage tools
Grid Inspector tool. Enables you to focus
closely on a region or point within a coverage
grid, furthering your analysis efforts.
Single object coverage. Evaluates thedynamic coverage to a single object insteadof a continuous area – for example coveragealong a flight path, an orbit, or a truck route.

Volumetric analysis
Volumetric analysis combines the SpatialAnalysis tool with the capabilities of
Coverage’s Volumetric object by evaluatinguser-defined volumes that are displayed asinterpolated values across grids points inthe 3D window. 3D grids can be defined inany coordinate system, relative to Earth or
any STK object.
The Spatial Analysis tool requires
Analysis Workbench.

Coverage definition reports
and graphs
Coverage reports and graphs provide theability to dissect your overall performance.
All data computed during the analysis isavailable to inspect at the asset-specific levelor system level. Percent contributions, gaps,
and time to cover values can all be analyzed.

Figure of Merit reports
and graphs
Provides analysis of minimum, maximum,
and average values over the coverage gridas well as percent satisfied results over theanalysis period.

2D and 3D coverage visualization
Coverage results can be displayed
statically (an accumulation of figure of
merit satisfaction over the analysis interval)or during animation (instantaneous
satisfaction of the figure of merit for thatparticular time step).
Each grid point is color-coded based on theuser-defined color selection or color rampalong with a defined number of contours orlevels. To generate the smoothest looking
contours, you can optionally choose tointerpolate between grid points.

Automation or third-party
application access to Coverage
Coverage can be accessed via the STK
Connect interface, the STK Object Modelinterface, and the STK scripting interface
which supports Perl, VB Script or MATLAB.

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