Process scan if enough time has elapsed since the previous one

[spmaniato]

This PR is tied to ros-perception/slam_karto#11 ⚠️

Adds a new parameter, MinimumTimeInterval, which is similar in spirit to the existing MinimumTravelDistance and MinimumTravelHeading. It's also similar to GMapping's temporalUpdate parameter. The new parameter defaults to 3600 (seconds), which effectively disables it. (Instead, I can make it such that negative values disable it, like in GMapping.)

From the header file documentation:

Sets the minimum time between scans. If a new scan's time stamp is
longer than MinimumTimeInterval from the previously processed scan,
the mapper will use the data from the new scan. Otherwise, it will
discard the new scan if it also does not meet the minimum travel
distance and heading requirements. For performance reasons, it is
generally it is a good idea to only process scans if a reasonable
amount of time has passed. This parameter is particularly useful
when there is a need to process scans while the robot is stationary.
Default value is 3600 (seconds), effectively disabling this parameter.

Here are two quick videos demonstrating the usefulness of such as parameter when the robot is stationary but there is a need for processing laser scans:

Before (not very interesting and laser scans go to waste):

minimum_travel_distance:  0.30    # [m]
minimum_travel_heading:   0.50    # [rad]

After (Karto processes laser scans while the robot is stationary):

minimum_time_interval:    1.0     # [sec]
minimum_travel_distance:  0.30    # [m]
minimum_travel_heading:   0.50    # [rad]

[mikeferguson]

Thanks for the contribution -- I'll merge the slam_karto changes after this has been released and made it's way through the buildfarm

[spmaniato]

I'll merge the slam_karto changes after this has been released and made it's way through the buildfarm

@mikeferguson Just a reminder that we need a release of open_karto in order to eventually merge ros-perception/slam_karto#11 No rush and thank you for your time 🙂