This guide describes the files that current-generation Spotter buoys generate and save to their onboard SD card.

For a detailed description of the log files generated by Bristlemouth systems in Bristlemouth-enabled Spotters, refer to: Spotter 3 Bristlemouth SD Card Data Guide.

</aside>

For a detailed description of the log files generated by legacy Spotters, refer to: Spotter SD Card Data Guide (Legacy).

</aside>

<aside>

Table of Contents

</aside>

Data storage

Format

SD cards must be full-sized (i.e., not micro) and in FAT32 format.

Capacity

The SD card shipped with Spotter has a capacity of 16 GB.

Spotters can support SD cards with up to 2 TB of capacity as long as they are in the correct format (see above).

Logging volume

Spotters without Smart Mooring will typically generate around 12 MB of SD card data per day under default logging configurations, which works out to around 5 GB per year. Logging volume will increase significantly during certain states, for example, due to errors or a heavily depleted battery.

Smart Mooring data logging volume is dependent on the connected nodes and sampling configuration (see Smart Mooring Sensors). For reference, a default Sofar Temperature Sensor configuration will produce an additional 2.5 MB of log data per day.

Average daily log storage sizes can be found in the following table:

Log name	Default daily logging volume
`SYS.log`	2 kB
`LOC.csv`	51.84 kB
`FLT.csv`	10,800 kB
`SPC.csv`	290 kB
`SST.csv`	31 kB
`BARO.csv`	33 kB
`PWR.csv`	169 kB
`GMN.csv`	195 kB
`HTU.csv`	39 kB
`CFG.log`	1 kB
`ERR.log`	5 kB
`MS.log`	20 kB
`SM/FM/TM/PM.log`	380 kB
`NCD.log`	105 kB (see note below)
`GPS.log`	70 kB
`IRI.log`	1 kB
`HDR.log`	75 kB
TOTAL	12.27 MB

The NCD.log’s daily logging can vary greatly depending on whether or not HDR is enabled and a hydrophone is attached.

</aside>

Log files

Filename format

Spotter saves data to the log folder on its onboard SD card with the following filename format:

<log_session_id>_<file_type>.CSV / <log_session_id>_<file_type>.LOG

To limit the maximum size of individual files and minimize the damage of file corruption, all files are split into numbered log sessions. The log session ID increments on every system boot and whenever an individual file in the session exceeds 1GB. Also, if Spotter is unable to obtain real GPS time at system boot, the log session ID will increment again once it obtains real GPS time.

All files with the same log session ID (e.g., 0003_SYS.log and 0003_GMN.csv) can be considered concurrent.

Timestamps

By default, all logs ending in .csv have timestamps in Unix epoch format (i.e., number of seconds since 00:00:00 UTC on 1 January 1970) in the UTC time zone (e.g., 1648656721).