Graph Reduction: visual words not referenced by any nodes in WM or LTM are still saved to database about rtabmap HOT 2 OPEN

Is it possible to add an option to keep the new node and remove the old node on graph reduction? If an environment continues changing, new nodes will capture new environment information, while old nodes will gradually become outdated. Therefore, if the new nodes are kept and the old ones are reduced, the entire system can better meet the needs of lifelong SLAM. I'm not sure if this could cause other problems.

from rtabmap.

One problem I can see is the map could drift over time. However, if we don't care too much about global position, that could be interesting to try. Currently, removing a node from working memory (WM) can be slightly more complicated than the one just added in short-term memory (STM), as we may have to change links in database (for nodes in long-term memory (LTM) linking the node in WM). But it could be doable, with maybe a new parameter to trigger this approach on graph reduction.

Another thing is that we may want to keep the old version to localize on later, in particular in cyclic environmental changes (day->night, seasons...).

from rtabmap.