0001-renaming-sparse-pose-graph.md

Renaming the Sparse Pose Graph

Summary

The goal of this change is to improve readability of the code base by choosing a better name for the "sparse pose graph", e.g. "pose graph".

Motivation

Renaming "sparse pose graph" to just "pose graph" conveys almost the same information, i.e. the word "sparse" is mostly noise. The concept of a pose graph is well known in SLAM. Of all the features that this pose graph has being "sparse" is not particularly extraordinary. The expected outcome is a more readable code base. We want to do this change before version 1.0 while we do not guarantee stable option names since it will be harder to do afterwards.

Approach

• sparse_pose_graph directories are renamed pose_graph.
• SparsePoseGraph classes are renamed PoseGraph.
• sparse_pose_graph.lua is renamed pose_graph.lua and the word sparse is dropped from the options name.
• dependent configuration files (including other repositories) have to be updated to use the new options name.

Discussion Points

Is it not an advantage that Sparse Pose Graph is a reference to Sparse Pose Adjustment?

Sparse Pose Adjustment is an algorithm for optimizing a pose graph using a direct linear solver and inspired the current implementation in Cartographer. This is an implementation detail and might change in the future. Having a name that sounds as if it refers to the current inspiration of the implementation thus is an argument for changing the name.

Isn't a sparse pose a well known concept in SLAM?

No. The name refers to the sparsity of the graph not the pose. Removing "sparse" also gets rid of this misconception. A pose graph is a well known concept in SLAM, e.g. in the Sparse Pose Adjustment paper, 8 of the 9 mentions of a pose graph do not qualify it as "sparse".