The Content of FIT Files on a Garmin Device
Depending upon the specific device, Garmin fitness trackers can contain significant amounts of information that can be used to allow for the identification of time, date, distance travelled, speed, location, heart rate and various other details of the device/user at a particular time.
The device stores this information within fit files that can be found within the Activity folder within the main directory named Garmin.
By connecting the device to a PC, the files present on the Garmin device can be accessed using a suitable file manager and the fit files copied from it, either via Windows Explorer, for example, or through the use of a forensic application.
The Garmin fit files can be converted into readable CSV format using software such as FitToCSV which is available here: https://developer.garmin.com/fit/download/.
Once converted, the content can then be reviewed. The table includes each entry and titled columns for those entries, which include location, speed, distance etc along with a time and date for each entry recorded.
Garmin Location Record
The location of the device within each entry is stored next to the columns containing the text position_lat and position_long.
To convert these stamps into a format that can be input to standard mapping application or sites, the entries are divided by 11930465 to produce the north and east coordinates more commonly used.
This information can then be used to identify the specific location of the device at a specific time that has been recorded via the device’s inbuilt GPS sensor.
This information can allow for the tracking or tracing of movement of the device on specific dates or times. These dates and times stored within the Garmin fit files also require conversion to real or local time.
Garmin Timestamp
The timestamp is also recorded within each entry of the fit file and is located next to the column that displays the text timestamp.
However, the text is stored as a number it is stored as an epoch. However, rather than relating to the number of seconds since 1st January 1970 as standard in Unix, Garmin took the time from 31st December 1989, meaning that different conversion is required.
This conversion can be carried out by adding 631065600 seconds to the relevant timestamp entry witihn the fit file and entering that to a standard Unix epoch convertor.
Alternatively, a convertor specifically for Garmin Epoch conversion can be used in order to identify the specific time and date that the entry was recorded.
A Garmin specific epoch convertor is provided below:
When the device is using the GPS as part of the fitness tracking function, the device automatically synchronises time with GPS Time, therefore any timestamps associated with an entry within the fit file should be accurate.
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