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MPS Output - Multi-Sequence Trajectory

Multi-Sequence Trajectory (MST), called Multi-SLAM in the MPS CLI and Aria Studio, processes two or more recordings captured in the same space. It generates the standard MPS SLAM outputs for every recording and aligns the outputs expressed in world coordinates into a shared coordinate frame.

You can request MST with the MPS CLI or Aria Studio. With the CLI, pass the VRS recordings as inputs and select a separate output directory:

aria_mps multi -i <VRS file or directory> -o <output directory>

MST is intended for two or more recordings; use aria_mps single for one recording. All recordings in one multi-recording request must come from the same Aria device generation and use a recording profile with CV cameras and IMU enabled. If the service cannot align every recording into one component, the result can contain multiple disconnected components, as described below.

For request and processing failures, see MPS Troubleshooting.

Output structure​

The default extracted output directory contains one numbered subdirectory per input recording, a group-level summary.json, and a vrs_to_multi_slam.json mapping file:

multi_slam_output/
├── 0/
│   ├── slam/
│   │   ├── closed_loop_trajectory.csv
│   │   ├── online_calibration.jsonl
│   │   ├── open_loop_trajectory.csv
│   │   ├── semidense_observations.csv.gz
│   │   ├── semidense_points.csv.gz
│   │   └── summary.json
│   └── vrs_health_check.json
├── 1/
│   ├── slam/
│   │   └── ...
│   └── vrs_health_check.json
├── summary.json
└── vrs_to_multi_slam.json

Each slam/ directory uses the same per-file schemas as a single-recording SLAM request:

vrs_health_check.json contains the client-side health check for that recording. The root-level summary.json contains the processing summaries for the group-level MST stages; each slam/summary.json describes the SLAM processing for one recording.

By default, the CLI deletes each downloaded slam.zip archive after extracting it into slam/. If the delete_zip setting is disabled, slam.zip remains next to the extracted directory.

Map recordings to output directories​

vrs_to_multi_slam.json maps each input VRS path to its numbered output directory. Use this file instead of assuming that a recording has a particular directory number. For example:

{
  "/data/session/recording-1.vrs": "0",
  "/data/session/recording-2.vrs": "1"
}

Shared coordinate frames​

MST aligns the world-coordinate outputs from each recording:

  • closed_loop_trajectory.csv and semidense_points.csv.gz entries with the same graph_uid are expressed in the same world coordinate frame.
  • open_loop_trajectory.csv remains in a per-recording odometry frame identified by its session_uid.
  • A result can contain multiple disconnected alignment components. Data with different graph_uid values does not share a coordinate frame and must not be overlaid directly.

MST aligns spatial coordinate frames; it does not synchronize tracking_timestamp_us across recording sessions or devices. See MPS File Structure and Common Terminologies for timestamp and coordinate-frame definitions.