# SubmapQuery.srv

## Overview

`SubmapQuery.srv` queries a single submap for its texture data. It returns the current version of the submap and an array of textures that can be rendered.

## Request

| Field | Type | Description |
| --- | --- | --- |
| `trajectory_id` | `int32` | The trajectory that the submap belongs to. |
| `submap_index` | `int32` | The index of the submap within the trajectory. |

## Response

| Field | Type | Description |
| --- | --- | --- |
| `status` | `cartographer_ros_msgs/StatusResponse` | The outcome of the request; check `code` against `StatusCode.OK`. |
| `submap_version` | `int32` | The current version of the submap. |
| `textures` | `cartographer_ros_msgs/SubmapTexture[]` | The texture slices of the submap. |

## Usage

- The pair `(trajectory_id, submap_index)` uniquely identifies a submap.
- Consumers can cache the last seen `submap_version` and skip re-fetching when it has not changed.
- Each texture in `textures` follows the `SubmapTexture.msg` layout.