Cartographer_ros: How to load a map in the cartographer for the resumption of the cartographer in uncharted areas

[amburkoff]

On the first day, using cartographer, I create a corridor map and save it via map_saver.
On the second day, I need to load the map into the cartographer and continue creating the map in the unexplored rooms.
How to save a map from cartographer so that it can be loaded back into it and continue research in unknown areas?

[rdesc]

Step to save a map in a serialized state

1. rosservice call /write_state "filename: '$MAP_NAME.pbstream' include_unfinished_submaps: false" (TIP: press tab after /write_state to get arguments and note map gets saved by default to ~/.ros)

Map_saver only gives you the occupancy grid map (made by the cartographer_occupancy_grid_node) which is used purely for robot navigation stacks.

[koki-ogura]

And, how to load it to cartographer_node ?

[koki-ogura]

append load_state_filename to args.
<node name="cartographer_node" pkg="cartographer_ros" type="cartographer_node" args="-load_state_filename $MAP_NAME.pbstream" />

[Sanderi44]

One thing that could be useful would be to create a "LoadState" service that runs in the cartographer node. This service would simply call the Node::LoadState method. What I am unclear about is what will happen to the existing trajectory if LoadState is called in the middle of a trajectory. My expectation is that it will overwrite that trajectory and start from scratch with the loaded state. I will do some experimentation and report back.

[Maibaf]

It seems, that is is not possible to resume mapping with an .pbstream file. Is this correct?

The result i get, in 2D SLAM on loading the state file, is, that the cartographer overrides the existing map. Mapping starts at the same point on the loaded map (i think this is the (0/0) point) like in the previous ride.
If the cartographer would perform a global localization first on the loaded map, continuing the mapping would may be possible. Does anyone know more about this?

[nickvaras]

A trajectory should be finished before serializing to .pbstream. When mapping is restarted (and on the same starting point), a new trajectory is started.

[Ga0aG]

append load_state_filename to args.
<node name="cartographer_node" pkg="cartographer_ros" type="cartographer_node" args="-load_state_filename $MAP_NAME.pbstream" />

I tried it, but cartographer_ros only load a frozen trajectory, there is no prebuilt map.

[MichaelGrupp]

Original question was answered.