feat(slam): add cartographer_ros

2025-07-04 14:39:48 +08:00
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+.. Copyright 2017 The Cartographer Authors
+
+.. Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+..      http://www.apache.org/licenses/LICENSE-2.0
+
+.. Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+
+===========
+Terminology
+===========
+
+This documents a few common patterns that exist in the Cartographer codebase.
+
+Frames
+======
+
+global map frame
+  This is the frame in which global SLAM results are expressed. It is the fixed
+  map frame including all loop closure and optimization results. The transform
+  between this frame and any other frame can jump when new optimization results
+  are available. Its z-axis points upwards, i.e. the gravitational acceleration
+  vector points in the -z direction, i.e. the gravitational component measured
+  by an accelerometer is in the +z direction.
+
+local map frame
+  This is the frame in which local SLAM results are expressed. It is the fixed
+  map frame excluding loop closures and the pose graph optimization. For a given
+  point in time, the transform between this and the global map frame may change,
+  but the transform between this and all other frames does not change.
+
+submap frame
+  Each submap has a separate fixed frame.
+
+tracking frame
+  The frame in which sensor data is expressed. It is not fixed, i.e. it changes
+  over time. It is also different for different trajectories.
+
+gravity-aligned frame
+  Only used in 2D. A frame colocated with the tracking frame but with a
+  different orientation that is approximately aligned with gravity, i.e. the
+  gravitational acceleration vector points approximately in the -z direction. No
+  assumption about yaw (rotation around the z axis between this and the tracking
+  frame) should be made. A different gravity-aligned frame is used for different
+  trajectory nodes, e.g. yaw can change arbitrarily between gravity-aligned
+  frames of consecutive nodes.
+
+
+
+Transforms
+==========
+
+local_pose
+  Transforms data from the tracking frame (or a submap frame, depending on
+  context) to the local map frame.
+
+global_pose
+  Transforms data from the tracking frame (or a submap frame, depending on
+  context) to the global map frame.
+
+local_submap_pose
+  Transforms data from a submap frame to the local map frame.
+
+global_submap_pose
+  Transforms data from a submap frame to the global map frame.