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Substrate can open recorded data files and present them in a synchronized multi-panel layout. Scrub through time and every panel — 3D viewer, plots, GPS map, log messages — updates together. Two recording formats are supported.

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Synchronized Playback

Regardless of format, all recorded data shares the same playback controls:
Drag the timeline cursor to any point in the recording. All panels update simultaneously to reflect that moment in time.

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ULog Files

Open a PX4 .ulg file directly in Substrate for post-flight analysis. The editor automatically arranges a purpose-built layout.

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Automatic Layout

3D Viewer + GPS Map

Top row. The 3D viewer reconstructs the vehicle pose via interpolated position and attitude channels. The GPS map renders the ground track.

Plot Groups + Logs

Bottom row. Four plot groups display attitude, position, velocity, and sensor data. A log panel shows timestamped entries with severity coloring.

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What’s Included

DataSource
3D poseInterpolated from position + attitude channels (binary search + lerp)
GPS pathLatitude/longitude rendered as a 2D ground track and 3D spatial trace
Telemetry channelsAll logged topics available as plottable time-series
Mode timelineColor-coded bar showing controller mode transitions over time
Log messagesSeverity-colored entries (Error, Warning, Info, Debug) with search and filtering
ParametersStatic parameter values recorded at boot, browsable in a dedicated section

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Attitude Plots

Roll, pitch, and yaw are plotted by default. Both setpoint and estimated values are shown, making it straightforward to evaluate controller tracking during maneuvers.
Combine the mode timeline with attitude plots to find oscillations or tracking errors that correlate with specific mode transitions.

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MCAP Recordings

MCAP files recorded during live simulation sessions contain the full data stream — scene graph updates, telemetry, images, transforms, and point clouds. Open an .mcap file to replay the session with the same multi-panel layout.

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What’s Included

DataSource
3D sceneFull scene graph with meshes, materials, and pose updates
TelemetryAll topics that were streaming during the recording
ImagesCamera feeds captured during the session
TransformsTF tree history with interpolated playback
Point cloudsLidar and depth sensor data
MCAP recordings are richer than ULog files because they capture the complete simulation state, not just autopilot telemetry. Use them when you need to review 3D scene behavior, sensor output, or multi-robot interactions.
Record MCAP files during a live simulation using the recording toggle in the telemetry panel. See the Record & Replay guide for details.

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Log Messages

Both formats support log message display with severity-based coloring:
  • Red — Error (levels 0-3)
  • Yellow — Warning (level 4)
  • Blue — Info (levels 5-6)
  • Gray — Debug (level 7+)
Use the search field and severity filter to narrow down entries when diagnosing issues.