19.8.4 DAS Time Array

The Times arrays contain the ‘scan’ or ‘trace’ times at which the raw, FBE and spectrum arrays were acquired or processed:

• For raw data, these are the times for which all loci in the ‘scanned’ fiber section were interrogated by a single pulse of the DAS measurement system.

• For the processed data, these are the times of the first sample in the time window used in the frequency filter or transformation function to calculate the FBE or spectrum data.

Figure 18.1.4-1 shows traces/scans as vertical columns of dots. Note that these Times arrays contain the times in Unix time (microseconds passed since 1 January 1970).

Because these UNIX times are difficult to decipher by a human user, the Times arrays contain a StartTime and EndTime in human-readable format, for example 2015-07-20T07:23.45.678000+00:00 corresponding to UNIX time 1437377025678000 in microseconds. Note that the timestamp must comply with ISO-8601 format and always include time zone.

StartTime and EndTime always refer to the full raw/FBE/spectra dataset across all file parts. EndTime is optional, but StartTime is required. PartStartTime and PartEndTime are used to keep track of start and end times of individual recordings (see next section).As mentioned previously, EndTime is optional for a continuous recording because the recording end time may not be known upfront.