Constant distance

Plugin name: constant_distance
Implementation: openstb.simulator.system.ping_times.ConstantDistance

This plugin models a system operating with a constant ping repetition distance, i.e., which adapts the interval between pings to compensate for changes in velocity. The desired distance between pings is given by the distance parameter, a floating-point value in metres. The start_offset parameter gives the distance (as a floating-point value in metres) between the start of the trajectory and the first ping being transmitted. The minimum distance between transmission of the final ping and the end of the trajectory is given by the end_offset parameter, another floating-point value in metres. These three parameters are required; the two offsets can be set to zero if not relevant.

Internally, the plugin calculates the mean speed of the system throughout the trajectory. Dividing the desired ping distance by this mean speed gives the mean time interval between pings. It then samples the trajectory a set number of times in each of these intervals, giving a mapping between time and cumulative distance travelled along the trajectory. This mapping is interpolated with a piecewise cubic hermite interpolating polynomial (PCHIP) interpolator to find the time corresponding to each desired distance.

The sampling_factor parameter sets the number of samples taken within each mean time interval to generate the mapping. It is an integer value which defaults to 10 if not explicitly set.