How to manually modify costmap from navigation stack? [closed]

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Hello everyone,

I would like to come up with a solution that will make my robot not to "cross" the way of moving objetcs (to be more precise, people). I thought that one way to do this might be to "inflate" the size of the costmap's obstacle in the direction of the movement.

Thanks to openni_tracker I can have people's position and estimate their speed. The problem is that I don't know a way (if any) to access the costmap used in navigation stack. Any ideas?

Thank you in advance.