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USB NMEA Data Logger


The USB NMEA data logger is sold as a unit integrated within our GPSBOXKBD GPS and GPS / Depth video overlay units. It cannot be ordered or used separately. It logs the raw NMEA data sentences shown below from the GPS receiver and separate depth sensor as a plain text file on a USB memory drive. It does not record video. The NMEA data's time and date is the only index to relate it to any separately recorded video file. No USB memory device is included.

USB Datalogger Compatibility
Compatible GPSBOXKBD units GPS data logged Depth data logged






*The GPSBOXKBD-DT used with a combined GPS / depth sounder unit with a single GPS and depth serial data stream.

NMEA data sentences logged.
Logged from GPS receiver ( $XXRMC is required, other are optional ).
Logged from depth transducer ( if present ).

USB Datalogger Operation
The USB data logger operates completely automatically. It does not require any setup or configuration. There are no user controls. A green activity LED indicates the status of the data logger. It is off when no USB memory is inserted. The activity LED lights up when a USB memory device is inserted and starts to flash when a file is opened and data is being logged. When using the GPSBOXKBD, GPSBOXKBD-DT, or GPSBOXKBD-XDT units with an external GPS receiver, the $XXRMC data sentence is required, other sentences shown below will be logged if they are present. Sentences not shown will be ignored by the data logger.
Filenames are generated automatically in the format mmhhddmm.log so a file opened at 13:11 UTC on the 28th February would have the file name 13112802.log. The time and date are always UTC taken directly from the NMEA data. Any time zone offset which is shown on the video overlay will have no effect on the time and date used for the data logger files. The data logger does not check the USB memory device for available space so it is the responsibility of the user to ensure there is adequate space by clearing old files.

A file is opened when the first valid GPRMC data sentence is received. Each file will remain open for one hour and will store the NMEA data sentences shown above. All other data sentences will be ignored. After one hour a new file will be opened with a new filename if the GPS data remains valid. If the GPS data is not valid, the data logger will wait until valid data is received before opening a new file. Data is written to the open file approximately once per second. The video overlay unit can therefore be switched off, or the USB memory can be removed, while the unit is logging data and only approximately one second of data will be lost. When the USB memory is re-inserted a new file will be opened. The USB memory device used should have a write speed of at least 8mb/s. Lower write speeds may result in data loss at 5Hz or 10Hz update rates. The Sandisk Cruzer Fit ( not included ) meets this specification.

document Documentation

The plain text nmea *.log files created by the data logger can be directly imported into recent versions of Google Earth.

Example GPS log files

Recorded using the GPSBOXKBD+5HZ with the USB NMEA data logger.

London - Pontefract

London - Luton













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