AssembleTrajectories Module

Module contents

template<typename TrajectoryT, typename PointIteratorT>
class AssembleTrajectories

Assemble time-sorted points into trajectories

We often receive input data as sequences of points sorted by timestamp. In order to manipulate these data sets as trajectories instead of as isolated points we must perform some sort of connect-the-dots operation to group them together. This class implements that operation.

Suppose for the sake of argument that our input is sorted first by object ID and second by increasing timestamp. Now consider the block of points corresponding to a single object ID. We divide that into one or more trajectories as follows:

  • If too much time (as specified by the separation_time parameter) has elapsed between one point and the next, one trajectory has ended and another begins.

  • If too much distance (as specifide by the separation_distance parameter) lies between one point and the next, one trajectory has ended and another begins.

We implement AssembleTrajectories as an iterator. It consumes an input stream of points sorted by timestamp (not by object ID) and produces complete trajectories. Internally, it keeps track of all the object IDs seen recently and applies the process above to identify and emit complete trajectories.

We can also set a third parameter (minimum_trajectory_length) that silently rejects trajectories that do not contain enough points to be interesting.

Public Types

typedef TrajectoryT trajectory_type
typedef trajectory_type::point_type point_type
typedef AssembleTrajectoriesIterator<point_type, PointIteratorT, trajectory_type> iterator

Public Functions

inline AssembleTrajectories()

Instantiate AssembleTrajectories using the default assembly configuration.

Set the default values for a trajectory

Default configuration is:

  • SeparationDistance = 100

  • SeparationTime = Duration(minutes(30))

  • MinimumTrajectoryLength = 2

  • CleanupInterval = 10000

inline AssembleTrajectories(PointIteratorT rangeBegin, PointIteratorT rangeEnd)

Instantiate AssembleTrajectories from a range of elements and default configuration.

If you have a container of points you can use this constructor to create and populate the tree in one swell foop instead of adding elements one at a time.

Set the default values for a trajectory

Default configuration is:

  • SeparationDistance = 100

  • SeparationTime = Duration(minutes(30))

  • MinimumTrajectoryLength = 2

  • CleanupInterval = 10000

Parameters:

  • range_begin – [in] Iterator pointing to beginning of input points

  • range_end – [in] Iterator pointing past end of input points

inline AssembleTrajectories(AssembleTrajectories const &other)

Copy Constructor, create AssembleTrajectories with trajectory data from another trajectory.

Parameters:

other – [in] AssembleTrajectories instance

inline virtual ~AssembleTrajectories()

Destructor.

inline AssembleTrajectories &operator=(AssembleTrajectories const &other)

Assign a AssembleTrajectories to the value of another.

Parameters:

other – [in] AssembleTrajectories to assign value of

Returns:

AssembleTrajectories with the new assigned value

inline bool operator==(AssembleTrajectories const &other) const

Check whether one AssembleTrajectories is equal to another by comparing the properties.

Two items are equal if all of their properties are equal.

Parameters:

other – [in] AssembleTrajectories for comparison

Returns:

Boolean indicating equivalency

inline bool operator!=(AssembleTrajectories const &other) const

Check whether two AssembleTrajectories are unequal.

Parameters:

other – [in] AssembleTrajectories for comparison

Returns:

Boolean indicating equivalency

inline iterator begin()

Return an iterator to the first parsed point.

Note

that any changes you make to the parser configuration will invalidate existing iterators.

Returns:

Iterator to first parsed point

inline iterator end()

Return an iterator to detect when parsing has ended.

This iterator is guaranteed to not point at any valid TrajectoryPoint. The only time when begin() == end() will be when all points have been parsed from the input stream.

Returns:

Iterator past end of point sequence

inline void set_input(PointIteratorT const &forefront, PointIteratorT const &rearguard)

Set the start and end points of the trajectory

Parameters:

  • forefront – [in] Start point

  • rearguard – [in] End point

inline void set_separation_time(Duration const &d)

Set the time between each point in the trajectory

Parameters:

d – [in] Time duration between each point in the trajectory

inline void set_separation_distance(double d)

Set the distance between each point in the trajectory

Parameters:

d – [in] Distance between each point in the trajectory

inline void set_minimum_trajectory_length(std::size_t len)

Set the minimum length a trajectory can be

Parameters:

len – [in] Length of the trajectory

inline void set_cleanup_interval(int points_between_cleanup)

Set the interval that the trajectory points will be cleaned up

Parameters:

points_between_cleanup – [in] Number of points to clean up

inline Duration separation_time() const
Returns:

The separation time of the trajectory points

inline double separation_distance() const
Returns:

The separation distance of the trajectory points

inline std::size_t minimum_trajectory_length() const
Returns:

The minimum length a trajectory can be

inline int cleanup_interval() const

Protected Functions

inline virtual void set_default_configuration()

Set the default values for a trajectory

Default configuration is:

  • SeparationDistance = 100

  • SeparationTime = Duration(minutes(30))

  • MinimumTrajectoryLength = 2

  • CleanupInterval = 10000

Private Members

PointIteratorT PointBegin
PointIteratorT PointEnd
Duration SeparationTime
double SeparationDistance
std::size_t MinimumTrajectoryLength
int CleanupInterval