Merging Sessions

About

You can merge multiple mapping sessions into a single map using the offline viewer. This is useful when you want to create a large map from multiple mapping sessions, or when you want to improve the global consistency of the map by merging multiple sessions.

Note

The map data is likely to be broken when warnings like [global] [warning] X34 -> E69 is missing are shown, and the optimization may get corrupted when merging broken map data. Before merging sessions, make sure each map data is not broken. A broken map can be repaired by clicking Recover graph. You have to repair maps one by one (Load a broken map -> repair it -> save it -> close it, then do so for the next map).

Example

Example dump data:

• mmm.tar.gz [32MB] (3 indoor sessions)
• inarimae_mmm.tar.gz [245MB] (3 sessions in large outdoor)

Start offline viewer

ros2 run glim_ros offline_viewer

Open mapping sessions

1. Open the first session : File -> Open New Map -> Select the first dump directory -> Select Yes on the dialog to enable optimization.
2. Open the second session : File -> Open Additional Map -> Select the second dump directory.

Merge sessions

1. Click Merge sessions
2. Choose the default registration parameter set (Indoor or Outdoor) and click OK
3. Align point clouds using automatic or manual alignment
   • Automatic alignment : Run global registration and check if the point clouds are roughly aligned
   • Manual alignment : Roughly align the source points (green) with the target points (red) by manipulating the Gizmo UI.
4. Click Run fine registration to perform ICP matching
5. Click Create factor to merge sessions

Fuse sessions (Global matching cost minimization)

1. Click Find overlapping submaps to create matching cost factors between overlapping submaps. This improves the global consistency between sessions.
2. Click Optimize several times to run optimization steps (Or click the check box to continuously run optimization)

Merge result	Merge result (Colored by session ID)	Factor graph