Navigation costmap parameter unknown_cost_value
Hello Does anyone know why the costmap_2d parameter "unknown_cost_value" cannot be set to 0 or lower. My understanding is that a costmap with static_map set to true will take in an occupancy_grid from the map topic. It then uses this unknown_cost_value to set all the corresponding cells with this value as unknown space in the newly created costmap. Since occupancy grids from the map topic have values at -1 for unknown space 0 for free space and 100 for occupied space it seems I can't set the unknown space for the cost map to be the same as the unknown_space in the map. It works fine if I set the unknown_cost_value larger then 0 to 100 for example but this then sets the unknown space in the cost map to be equal to the occupied space in the map.
The inconsistency is also noted here http://answers.ros.org/question/38765/occupancygrid-vs-costmap/