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Enabled? Checkbox
– Uncheck this box if you only want to do GNSS based loop closure and do
not want Stencil to do scan matching where trajectories approach each other.
Matching Threshold (5000)
– Minimum threshold to accept scan matches during the process of
aligning the two patches from each part of the trajectory that comes close to each other.
Match Distance
(4.0)
– This is the distance between sensor poses of the
gap on the map to be closed.
This could be the distance between the
two end points of the trajectory if you actually started and stopped at
the same location as shown to the right, but it would be better in this
case to select the checkbox indicating “End at start point?” This way
you can use a smaller value for the Match Distance to avoid having
nearby trajectories to be treated as overlapping.
A good way to estimate the Match Distance where the start and stop
location is not the same is to measure the distance between the same object in the point cloud
seen at different time. By looking at your point cloud by time, you can see the same object as two
colors separated by some distance. You should set the Match Distance to be 50 % larger than the
largest Match Distance you can see in this manner.
Four meters is a good value unless the gap is larger than the default value or you have situations
where you want to isolate trajectories that are closer to each other. Consider the case of a
parking garage, where the floors might be 3 meters apart. The Loop Closure Tool might match
one floor to the one above or below it if you leave this at 4 meters. We will come back to this
specific case when we talk about the match regions in the next paragraph.
You can think of Match Distance as a sphere reaching in all directions where the parameter can be
tuned for trajectories that don’t cross but come close to each at places other than the starting and
