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Scatterer-class object for target strength estimation

Source: R/scatterer.R
Scatterer-class.Rd

The acousticTS package uses a variety of defined S4-class objects comprising different types of scatterers, such as fish with gas-filled swimbladders (SBF) and fluid-like crustaceans (FLS).

Value

An object from the Scatterer S4 class hierarchy.

Slots

metadata

List containing relevant metadata

model_parameters

Model parameters necessary for predicting TS

Data Organization

metadata:

A list comprising any identifying information associated with the scatterer. The default metadata entry includes ID that uses a default character value of "UID" (i.e. ID = "UID"). This can otherwise be formatted in any manner for book keeping purposes.

body/bladder:

A list that includes information relevant to the scatterer's position vector, material properties, tilt/orientation, etc. For some scatterers, this may only include body, but other targets may have an additional parameter such as bladder. Generally, each entry includes:

  • rpos: the relevant position vector (r0) that includes axes such as x, y, z, etc., that depend on the type of scatterer being used.

  • radius: in some cases this includes the radius measurements for each cylinders depending on the type of scatterer object.

  • theta: the orientation of the scatterer relative to the transmitting transducer or sound source (θanimal) that can be represented either by degrees or radians, although all functions require radians.

  • g, h: material properties that represent the density and sound speed contrasts (g and h, respectively) relative to the ambient/surrounding fluid. Some targets may instead have standard sound speed (canimal, m s-1) and density (ρanimal, kg m3).

shape_parameters:

A list that includes metadata pertaining to the shape of the scatterer and any other features of interest (e.g. gas-filled swimbladder). Generally, each entry includes: overall body length, the number of discrete cylinders that make up the shape (if applicable), and the units related to both θanimal (e.g. rad, °) and length (e.g. mm, m).

model_parameters:

A list that contains relevant model parameterization once an object has been initialized for modeling σbs. This is typically broken up into three categories:

  • parameters: A list that includes information such as frequency (Hz), acoustic wavenumber (i.e. k), etc.

  • medium: A data.frame including information such as the material properties of the ambient medium.

  • scatterer: A list containing summarized information used to parameterize certain scattering models.

model:

A list that collects model results from one or more models in the linear domain (i.e. σbs).

Supported Scatterers

  • Elastic-based scatterers (ELA)

  • Composite multi-component scatterers (CSC)

  • Backboned fish (BBF)

  • Calibration spheres (CAL)

  • Elastic-shelled scatterers (ESS)

  • Fluid-like scatterers (FLS)

  • Gas-filled scatterers (GAS)

  • Swimbladdered fish (SBF)

Examples

methods::getClass("Scatterer")
#> Class "Scatterer" [package "acousticTS"]
#> 
#> Slots:
#>                                         
#> Name:          metadata model_parameters
#> Class:             list             list
#> 
#> Known Subclasses: 
#> Class "ELA", directly
#> Class "CSC", directly
#> Class "GAS", directly
#> Class "FLS", directly
#> Class "ESS", by class "ELA", distance 2
#> Class "CAL", by class "ELA", distance 2
#> Class "BBF", by class "CSC", distance 2
#> Class "SBF", by class "GAS", distance 2