Platforms

class stonesoup.platform.base.Platform(states, position_mapping, rotation_offsets=None, mounting_offsets=None, sensors=None, velocity_mapping=None)

Bases: stonesoup.types.state.StateMutableSequence, abc.ABC

A platform that can carry a number of different sensors.

The location of platform mounted sensors will be maintained relative to the sensor position. Platforms move within a 2 or 3 dimensional rectangular cartesian space.

A simple platform is considered to always be aligned with its principle velocity. It does not take into account issues such as bank angle or body deformation (e.g. flex).

Note

This class abstract and not intended to be instantiated. To get the behaviour of this class use a subclass which gives movement behaviours. Currently these are FixedPlatform and MovingPlatform

Parameters

• states (Sequence[State]) – A list of States which enables the platform’s history to be accessed in simulators and for plotting. Initiated as a state, for a static platform, this would usually contain its position coordinates in the form [x, y, z]. For a moving platform it would contain position and velocity interleaved: [x, vx, y, vy, z, vz]

• position_mapping (Sequence[int]) – Mapping between platform position and state vector. For a position-only 3d platform this might be [0, 1, 2]. For a position and velocity platform: [0, 2, 4]

• rotation_offsets (MutableSequence[StateVector], optional) – A list of StateVectors containing the sensor rotation offsets from the platform’s primary axis (defined as the direction of motion). Defaults to a zero vector with the same length as the Platform’s position_mapping

• mounting_offsets (MutableSequence[StateVector], optional) – A list of StateVectors containing the sensor translation offsets from the platform’s reference point. Defaults to a zero vector with the same length as the Platform’s position_mapping

• sensors (MutableSequence[ForwardRef('BaseSensor')], optional) – A list of N mounted sensors. Defaults to an empty list

• velocity_mapping (Sequence[int], optional) – Mapping between platform velocity and state dims. If not set, it will default to [m+1 for m in position_mapping]

states: Sequence[stonesoup.types.state.State]

A list of States which enables the platform’s history to be accessed in simulators and for plotting. Initiated as a state, for a static platform, this would usually contain its position coordinates in the form [x, y, z]. For a moving platform it would contain position and velocity interleaved: [x, vx, y, vy, z, vz]

position_mapping: Sequence[int]

Mapping between platform position and state vector. For a position-only 3d platform this might be [0, 1, 2]. For a position and velocity platform: [0, 2, 4]

velocity_mapping: Sequence[int]

Mapping between platform velocity and state dims. If not set, it will default to [m+1 for m in position_mapping]

property position

Return the position of the platform.

Extracted from the state vector of the platform using the platform’s position_mapping. This property is settable for fixed platforms, but not for movable ones, where the position must be set by moving the model with a transition model.

sensors: MutableSequence[BaseSensor]

A list of N mounted sensors. Defaults to an empty list

mounting_offsets: MutableSequence[stonesoup.types.array.StateVector]

A list of StateVectors containing the sensor translation offsets from the platform’s reference point. Defaults to a zero vector with the same length as the Platform’s position_mapping

rotation_offsets: MutableSequence[stonesoup.types.array.StateVector]

A list of StateVectors containing the sensor rotation offsets from the platform’s primary axis (defined as the direction of motion). Defaults to a zero vector with the same length as the Platform’s position_mapping

property ndim

Convenience property to return the number of dimensions in which the platform operates.

Given by the length of the position_mapping

abstract property orientation

Return the orientation of the platform.

Implementation is case dependent and left to the Fixed/Moving subclasses

abstract property velocity

Return the velocity of the platform.

Implementation is case dependent and left to the Fixed/Moving subclasses

abstract is_moving() → bool

Return the True if the platform is moving, False otherwise.

abstract move(timestamp: datetime.datetime, **kwargs) → None

Update the platform position using the transition_model.

Parameters

timestamp (datetime.datetime, optional) – A timestamp signifying when the end of the maneuver (the default is None)

Notes

This methods updates the value of position.

Any provided kwargs are forwarded to the transition_model.

If transition_model or timestamp is None, the method has no effect, but will return successfully.

add_sensor(sensor: BaseSensor, mounting_offset: Optional[stonesoup.types.array.StateVector] = None, rotation_offset: Optional[stonesoup.types.array.StateVector] = None) → None

Add a sensor to the platform

Parameters

• sensor (BaseSensor) – The sensor object to add

• mounting_offset (StateVector, optional) – A StateVector with the mounting offset of the new sensor. If not supplied, defaults to a zero vector

• rotation_offset (StateVector, optional) – A StateVector with the rotation offset of the new sensor. If not supplied, defaults to a zero vector.

remove_sensor(sensor: BaseSensor) → None

Remove a sensor from the platform

Parameters

sensor (BaseSensor) – The sensor object to remove

pop_sensor(index: int)

Remove a sensor from the platform by index

Parameters

index (int) – The index of the sensor to remove

get_sensor_position(sensor: BaseSensor) → stonesoup.types.array.StateVector

Return the position of the given sensor, which should be already attached to the platform. If the sensor is not attached to the platform, raises a ValueError.

Parameters

sensor (BaseSensor) – The sensor for which to return the position.

Returns

The position of the sensor, taking into account the platform position and orientation and the mounting offset of the sensor.

Return type

StateVector

get_sensor_orientation(sensor: BaseSensor) → stonesoup.types.array.StateVector

Return the orientation of the given sensor, which should be already attached to the platform. If the sensor is not attached to the platform, raises a ValueError.

Parameters

sensor (BaseSensor) – The sensor for which to return the orientation.

Returns

The orientation of the sensor, taking into account the platform orientation and the rotation offset of the sensor.

Return type

StateVector

class stonesoup.platform.base.FixedPlatform(states, position_mapping, rotation_offsets=None, mounting_offsets=None, sensors=None, velocity_mapping=None, orientation=None)

Bases: stonesoup.platform.base.Platform

Fixed platform base class

A platform represents a random object defined as a State with fixed (but settable) position and orientation.

Note

Position and orientation are a read/write properties in this class.

Parameters

• states (Sequence[State]) – A list of States which enables the platform’s history to be accessed in simulators and for plotting. Initiated as a state, for a static platform, this would usually contain its position coordinates in the form [x, y, z]. For a moving platform it would contain position and velocity interleaved: [x, vx, y, vy, z, vz]

• position_mapping (Sequence[int]) – Mapping between platform position and state vector. For a position-only 3d platform this might be [0, 1, 2]. For a position and velocity platform: [0, 2, 4]

• rotation_offsets (MutableSequence[StateVector], optional) – A list of StateVectors containing the sensor rotation offsets from the platform’s primary axis (defined as the direction of motion). Defaults to a zero vector with the same length as the Platform’s position_mapping

• mounting_offsets (MutableSequence[StateVector], optional) – A list of StateVectors containing the sensor translation offsets from the platform’s reference point. Defaults to a zero vector with the same length as the Platform’s position_mapping

• sensors (MutableSequence[ForwardRef('BaseSensor')], optional) – A list of N mounted sensors. Defaults to an empty list

• velocity_mapping (Sequence[int], optional) – Mapping between platform velocity and state dims. If not set, it will default to [m+1 for m in position_mapping]

• orientation (StateVector, optional) – A fixed orientation of the static platform. Defaults to the zero vector

orientation: stonesoup.types.array.StateVector

A fixed orientation of the static platform. Defaults to the zero vector

property velocity

Return the velocity of the platform.

For a fixed platform this is always a zero vector of length ndim.

property is_moving

Return the True if the platform is moving, False otherwise.

move(timestamp: datetime.datetime, **kwargs) → None

For a fixed platform this method has no effect other than to update the timestamp.

class stonesoup.platform.base.MovingPlatform(states, position_mapping, transition_model, rotation_offsets=None, mounting_offsets=None, sensors=None, velocity_mapping=None)

Bases: stonesoup.platform.base.Platform

Moving platform base class

A platform represents a random object defined as a State that moves according to a given TransitionModel.

Note

Position and orientation are a read only properties in this class.

Parameters

• states (Sequence[State]) – A list of States which enables the platform’s history to be accessed in simulators and for plotting. Initiated as a state, for a static platform, this would usually contain its position coordinates in the form [x, y, z]. For a moving platform it would contain position and velocity interleaved: [x, vx, y, vy, z, vz]

• position_mapping (Sequence[int]) – Mapping between platform position and state vector. For a position-only 3d platform this might be [0, 1, 2]. For a position and velocity platform: [0, 2, 4]

• transition_model (TransitionModel) – Transition model

• rotation_offsets (MutableSequence[StateVector], optional) – A list of StateVectors containing the sensor rotation offsets from the platform’s primary axis (defined as the direction of motion). Defaults to a zero vector with the same length as the Platform’s position_mapping

• mounting_offsets (MutableSequence[StateVector], optional) – A list of StateVectors containing the sensor translation offsets from the platform’s reference point. Defaults to a zero vector with the same length as the Platform’s position_mapping

• sensors (MutableSequence[ForwardRef('BaseSensor')], optional) – A list of N mounted sensors. Defaults to an empty list

• velocity_mapping (Sequence[int], optional) – Mapping between platform velocity and state dims. If not set, it will default to [m+1 for m in position_mapping]

transition_model: stonesoup.models.transition.base.TransitionModel

Transition model

property velocity

Return the velocity of the platform.

Extracted from the state vector of the platform using the platform’s velocity_mapping. If the state vector is too short and does not contain the elements specified in the velocity_mapping this raises an AttributeError

property orientation

Return the orientation of the platform.

This is defined as a 3x1 StateVector of angles (rad), specifying the sensor orientation in terms of the counter-clockwise rotation around each Cartesian axis in the order \(x,y,z\). The rotation angles are positive if the rotation is in the counter-clockwise direction when viewed by an observer looking along the respective rotation axis, towards the origin.

The orientation of this platform is defined as along the direction of its velocity, with roll always set to zero (as this is the angle the platform is rotated about the velocity axis, which is not defined in this approximation).

Notes

A non-moving platform (self.is_moving == False) does not have a defined orientation in this approximations and so raises an AttributeError

property is_moving

Return the True if the platform is moving, False otherwise.

Equivalent (for this class) to all(v == 0 for v in self.velocity)

move(timestamp=None, **kwargs) → None

Propagate the platform position using the transition_model.

Parameters

timestamp (datetime.datetime, optional) – A timestamp signifying when the end of the maneuver (the default is None)

Notes

This methods updates the value of position.

Any provided kwargs are forwarded to the transition_model.

If transition_model or timestamp is None, the method has no effect, but will return successfully.

class stonesoup.platform.base.MultiTransitionMovingPlatform(states, position_mapping, transition_models, transition_times, rotation_offsets=None, mounting_offsets=None, sensors=None, velocity_mapping=None)

Bases: stonesoup.platform.base.MovingPlatform

Moving platform with multiple transition models

A list of transition models are given with corresponding transition times, dictating the movement behaviour of the platform for given durations.

Parameters

• states (Sequence[State]) – A list of States which enables the platform’s history to be accessed in simulators and for plotting. Initiated as a state, for a static platform, this would usually contain its position coordinates in the form [x, y, z]. For a moving platform it would contain position and velocity interleaved: [x, vx, y, vy, z, vz]

• position_mapping (Sequence[int]) – Mapping between platform position and state vector. For a position-only 3d platform this might be [0, 1, 2]. For a position and velocity platform: [0, 2, 4]

• transition_models (Sequence[TransitionModel]) – List of transition models

• transition_times (Sequence[datetime.timedelta]) – Durations for each listed transition model

• rotation_offsets (MutableSequence[StateVector], optional) – A list of StateVectors containing the sensor rotation offsets from the platform’s primary axis (defined as the direction of motion). Defaults to a zero vector with the same length as the Platform’s position_mapping

• mounting_offsets (MutableSequence[StateVector], optional) – A list of StateVectors containing the sensor translation offsets from the platform’s reference point. Defaults to a zero vector with the same length as the Platform’s position_mapping

• sensors (MutableSequence[ForwardRef('BaseSensor')], optional) – A list of N mounted sensors. Defaults to an empty list

• velocity_mapping (Sequence[int], optional) – Mapping between platform velocity and state dims. If not set, it will default to [m+1 for m in position_mapping]

transition_models: Sequence[stonesoup.models.transition.base.TransitionModel]

List of transition models

transition_times: Sequence[datetime.timedelta]

Durations for each listed transition model

property transition_model

Transition model

move(timestamp=None, **kwargs) → None

Propagate the platform position using the transition_model.

Parameters

timestamp (datetime.datetime, optional) – A timestamp signifying the end of the maneuver (the default is None)

Notes

This methods updates the value of position.

Any provided kwargs are forwarded to the transition_model.

If transition_model or timestamp is None, the method has no effect, but will return successfully.

This method updates transition_model, transition_index and current_interval: If the timestamp provided gives a time delta greater than current_interval the transition_model is called for the rest of its corresponding duration, and the move method is called again on the next transition model (by incrementing transition_index) in transition_models with the residue time delta. If the time delta is less than current_interval the transition_model is called for that duration and current_interval is reduced accordingly.