20.6.4 DAS FBE data

Topic Version2Published04/16/2018
For StandardPRODML v2.0

The Processed DAS FBE data object stores so-called frequency band extracted (FBE) data values calculated from raw DAS data recordings. The FBE data values are typically calculating the energy in a specific frequency band in a filter-window over the raw DAS data recording for each locus. This calculation produces a ‘trace’ (1D array) that contains an energy value for each locus, each time the filter-window was applied.

Figure 20.6.4-1 shows the attributes for the DAS FBE data object in the example file. Key attributes stored are: the FilterType applied while creating the frequency bands, and the StartIndex and NumberOfLoci recorded. Note that FBE trace loci can be a subset of the DAS raw data loci recorded for the DAS raw data from which the FBE data was generated. The OutputDataRate determines the Number of FBE traces output per second in the Das FBE object and is equal to or smaller than the DAS instruments PulseRate used to collect the DAS raw data. For each frequency band, the calculated energy value are stored in an FbeData Array presented by a 2D array as shown in Figure 20.6.4-2 . Each FbeData Array has a StartFrequency and EndFrequency attribute indicating in the FBE frequency band for which the data was calculated and stored. Figure 20.6.4-2 shows part of the first frequency band stored in FbeData[0] Array in the H5 part1.h5 sample file. The frequency band covers 0.5-1.0Hz and contains energy data for the first locus starting at index 10 (StartLocus) and covering 30 (NumberOfLoci) loci ranging with index numbers 10 to 39. There are 15 FBE traces (indexed 0 to 14).

Figure 20.6.4-1 DAS FBE attributes h5 file part1.h5 (rows = times, columns = loci).
Figure 20.6.4-2 DAS FBE attributes and array values and for frequency band FbeData[0] in h5 file part1.h5.