Legacy IMU packets present in PCAP but absent from OSF synchronized IMU fields

Software
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We are investigating an OS1-64 U02 capture processed with Ouster SDK and ouster-cli.

Sensor and capture details:

  • Sensor: OS1-64 U02
  • Firmware: v2.5.3
  • IMU profile: LEGACY
  • LiDAR mode: 1024x20
  • IMU UDP port: 7503
  • LiDAR UDP port: 7502

The original PCAP contains continuous raw IMU packets:

  • 10,605 total IMU packets across two PCAP files
  • Approximately 99.99 Hz
  • No duplicate timestamps
  • No timestamp reversals
  • No gaps above 15 ms
  • IMU timestamps overlap the LiDAR failure interval
  • Acceleration and gyro values are finite and nonzero

However, when the PCAP is opened through the SDK and converted to OSF, the LidarScan fields contain only:

  • RANGE
  • REFLECTIVITY
  • SIGNAL
  • NEAR_IR
  • FLAGS

No synchronized IMU fields are present.

The metadata also reports:

  • udp_profile_imu: LEGACY
  • imu_measurements_per_packet: 0
  • imu_packets_per_frame: 0

We tested direct PCAP SLAM with:

  • --deskew-method auto
  • --deskew-method imu_deskew
  • --deskew-method constant_velocity

The outputs were byte-identical. The CLI reports that synchronized IMU is unavailable and falls back to constant velocity.

Questions:

  1. Is it expected that FW 2.5.3 with the LEGACY IMU profile produces raw UDP IMU packets in the PCAP but no synchronized IMU fields in the OSF LidarScan stream?
  2. Can ouster-cli slam --deskew-method imu_deskew consume LEGACY UDP IMU packets directly from the original PCAP, or does it require synchronized IMU data in the newer profile?
  3. Is there an official Ouster-supported method to preserve or convert the LEGACY IMU packets into synchronized OSF IMU fields that SLAM can consume?
  4. Are synchronized OSF IMU fields dependent on firmware, sensor hardware revision, IMU profile, or all three?
  5. Would upgrading this OS1-64 U02 to a newer hardware revision with FW 3.2+ and ACCEL32_GYRO32_NMEA provide synchronized IMU fields and functional IMU deskew for offline PCAP SLAM?
  6. Is there an SDK or CLI command that can directly verify whether IMU samples were actually consumed by SLAM, beyond the selected deskew-method log message?

The distinction we need to establish is whether the limitation is:

  • Raw IMU capture,
  • PCAP decoding,
  • OSF conversion,
  • Firmware/profile support,
  • Hardware capability,
  • Or SLAM consumption.

We are at the point that we cannot figure out how to get past these problems and anything responses will be greatly appreciated.

2

Hi @mikehrub yes we don’t save the LEGACY IMU into OSF files. Since the LEGACY IMU data is not synchronized with LIDAR data it can’t be matched with a specific column data. Unlike the syncrhonized IMU which every measurement is matched to a specific column of LIDAR data. That’s why we don’t handle and save the LEGACY IMU and the recommendation is to always use the SYNCHORNIZED IMU data. All of REV7 sensors should support this format by upgrade to FW 3.2 with the exception of OS2.