Coverage Overview¶
AFSIM’s coverage capability collects the time history of interactions between grid points and other platforms, and post processes that information into measures of effectiveness (MOEs). This summary data can then be processed further, displayed, or used to make design decisions.
There are a few main concepts for AFSIM’s coverage capability: the coverage grid, which is the specification of the locations of interest for the MOE; the measure of effectiveness, which is the measurement being performed by the coverage computation; and the coverage computation itself, which ties together a grid, and a number of MOEs into a computation. Users wishing to perform a coverage computation will need to specify a grid and a coverage in their input.
A coverage computation monitors interactions between two sets of platforms in a simulation, and produces summary statistics of those interactions, MOEs. The interactions monitored will vary for each type of coverage (for example, WSF_SENSOR_COVERAGE monitors sensor interactions), but the monitored interactions always connect assets in the simulation, one each from two groups: grid assets and free assets (often denoted just ‘assets’ when that is clear from context).
Each grid asset is a platform instantiated by the simulation at one of the grid points for the grid selected by the coverage. The user specifies an existing platform type that will be the template for all of the created grid asset platforms.
Free assets are platforms existing in the simulation not tied to the grid (they are ‘free’ to move as they will) that can participate in the interactions with the grid assets instantiated in the simulation.
When specifying assets for a coverage object, the user will need to provide the name of a device (i.e., platform part) on the asset that is taking part in the interaction. Not every device is relevant for a given coverage type (for example, WSF_SENSOR_COVERAGE works with sensor), and selecting an incompatible type will result in initialization errors. In some instances, a coverage will only need one asset in an interaction to have a device. In those instances, the other asset can specify ‘none’ as their device.
A coverage computation can include as many measures of effectiveness as the user requires. Each available MOE (see Predefined Measures of Effectiveness) provides a separate way of summarizing the interaction history between the free and grid assets.
Coverage Grid¶
Coverage is computed at a fixed set of locations that form a coverage grid. Each coverage computation is required to specify the grid over which the computation is to occur, and multiple coverage computations can use the same grid.
AFSIM provides the following built-in grid types, each of which represents a family of grids that can be individually configured:
WSF_LAT_LON_GRID - A regular, rectangular grid in latitude and longitude.
WSF_ZONE_BASED_GRID - A regular grid in latitude and longitude, but with points filtered to be inside a specified zone.
WSF_DISTANCE_STEPPED_GRID - A regular, rectangular grid with separation given by distance.
WSF_EXISTING_PLATFORM_GRID - A grid formed from existing simulation platforms.
WSF_COMPOSITE_GRID - A grid formed by composing sub-grids.
Coverage¶
A coverage collects the time history of interactions between grid assets (platforms placed at the points of a grid) and free assets, and then processes that history into various measures of effectiveness (MOEs).
AFSIM provides the following built-in coverage types.
WSF_SENSOR_COVERAGE - Computes coverage from sensor interactions.
Measure of Effectiveness¶
A measure of effectiveness specifies how the collected interaction history for a coverage is processed into a usable number, typically summarizing the interactions.
AFSIM provides the following built-in measures of effectiveness.
WSF_ACCESS_DURATION_MOE - Measures the durations of access intervals of individual free assets.
WSF_COVERAGE_TIME_MOE - Measures the coverage time for the grid assets.
WSF_N_ASSET_COVERAGE_MOE - Measures how many free assets that a grid asset can access at a time.
WSF_NUMBER_OF_ACCESSES_MOE - Measures the number of coverage gaps for the grid assets.
WSF_NUMBER_OF_GAPS_MOE - Measures the number of coverage gaps for the grid assets.
WSF_SIMPLE_COVERAGE_MOE - Measures if grid assets have any interactions with a free asset.
WSF_REVISIT_TIME_MOE - Measures the revisit time for the grid assets.
WSF_TIME_AVERAGE_GAP_MOE - Measures the most likely coverage gap length one would find if the coverage interval were randomly sampled.
