GPS/GNSS Synchronization | Ouster Sensor Docs

For GPS wiring instructions, see GPS/GNSS Synchronization in the hardware user manual.

Configuring the Ouster Sensor

With GPS connections in place, configure the following parameters to synchronize the sensor’s timestamp to the GPS signal:

Parameter	Value
`timestamp_mode`	`TIME_FROM_SYNC_PULSE_IN`
`multipurpose_io_mode`	`INPUT_NMEA_UART`
`sync_pulse_in_polarity`	Match the polarity of the GPS PPS signal
`multipurpose_io_polarity`	Match the polarity of the GPS NMEA UART signal
`nmea_baud_rate`	Match the baud rate of the GPS output
`nmea_leap_seconds`	Current TAI–UTC offset — check leapsecond.com; at time of writing the value is `37`

Checking for Sync

After applying the configuration above, verify synchronization using GET /api/v1/time:

PPS lock — the response should include:
```
"sync_pulse_in": { "locked": 1 }
```
If not, recheck sync_pulse_in_polarity.
NMEA lock — the response should include:
```
"nmea": { "locked": 1 }
```
If not, recheck multipurpose_io_polarity and nmea_baud_rate.

NMEA decoding — last_read_message should contain a valid GPRMC sentence:

"decoding": { "last_read_message": "GPRMC,024041.00,A,5107.0017737,N,11402.3291611,W,0.080,323.3,020420,0.0,E,A*20" }

Timestamp — timestamp.mode should be TIME_FROM_SYNC_PULSE_IN and timestamp.time should reflect valid GPS time.

Example Response

Full example output from GET /api/v1/time:

{
  "timestamp": {
    "time": 1585881641.96139565999999,
    "mode": "TIME_FROM_SYNC_PULSE_IN",
    "time_options": {
      "sync_pulse_in": 1585881641,
      "internal_osc": 302,
      "ptp_1588": 309
    }
  },
  "sync_pulse_in": {
    "locked": 1,
    "diagnostics": {
      "last_period_nsec": 10,
      "count_unfiltered": 832,
      "count": 832
    },
    "polarity": "ACTIVE_HIGH"
  },
  "multipurpose_io": {
    "mode": "INPUT_NMEA_UART",
    "sync_pulse_out": {
      "pulse_width_ms": 10,
      "angle_deg": 360,
      "frequency_hz": 1,
      "polarity": "ACTIVE_HIGH"
    },
    "nmea": {
      "locked": 1,
      "baud_rate": "BAUD_9600",
      "diagnostics": {
        "io_checks": {
          "bit_count": 2938457,
          "bit_count_unfilterd": 2938457,
          "start_char_count": 832,
          "char_count": 66526
        },
        "decoding": {
          "last_read_message": "GPRMC,024041.00,A,5107.0017737,N,11402.3291611,W,0.080,323.3,020420,0.0,E,A*20",
          "date_decoded_count": 832,
          "not_valid_count": 0,
          "utc_decoded_count": 832
        }
      },
      "leap_seconds": 37,
      "ignore_valid_char": 0,
      "polarity": "ACTIVE_HIGH"
    }
  }
}