# SubmapEntry.msg

## Overview

`SubmapEntry.msg` describes a single submap in the map, including its trajectory, index, version, and pose, as well as whether it is frozen.

## Fields

| Field | Type | Description |
| --- | --- | --- |
| `trajectory_id` | `int32` | The trajectory that this submap belongs to. |
| `submap_index` | `int32` | The index of the submap within its trajectory. |
| `submap_version` | `int32` | The version of the submap; changes when the submap is updated. |
| `pose` | `geometry_msgs/Pose` | The pose of the submap in the map frame. |
| `is_frozen` | `bool` | Whether the submap is frozen (immutable). |

## Usage

- A submap is uniquely identified by the pair `(trajectory_id, submap_index)`.
- `submap_version` increases as the submap is refined during SLAM; consumers can use it to detect updated submaps.
- Frozen submaps are no longer modified and are typically candidates for map pruning.
- `SubmapEntry` instances are collected in the `submap` array of `SubmapList.msg`.