What's the correct usage of scale_factors?

[msadowski]

• Generic Sensor Format for Python version: 2.0
• Python version: 3.6.9
• Operating System: Ubuntu

Description

Hi!

I'm wondering if you would have some hints on the correct usage of scale_factor with gfs. I'm trying to develop a pipeline for converting sounding data from a custom system to gsf. In my initial trial, I was trying to add the time series intensity data before moving on with other fields, however no matter what I seem to try I get an error:

gsfpy3_09.GsfException: [-21] GSF Error: Illegal scale factor multiplier specified

What I Did

I tried to define the scale_factors as follows:

    scale_factors = c_gsfScaleFactors()
    scale_factors.numArraySubrecords = 1
    # Initialize the scaleTable with some example values
    for i in range(scale_factors.numArraySubrecords):
        scale_factors.scaleTable[i] = c_gsfScaleInfo(
            #set first bit to 1, and the rest to 0
            compressionFlag=c_ubyte(0x00),    # Example compression flag
            multiplier=c_double(0.0001),   # Example multiplier
            offset=c_double(0.0)        # Example offset
        )

    record.mb_ping.scaleFactors = scale_factors

and fill in the intensity array as follows:

    NumElements = 1
    BRBIntensityArray = c_gsfBRBIntensity * NumElements
    brb_array = BRBIntensityArray()
    brb_array[0].bits_per_sample = 8
    brb_array[0].applied_corrections = 0
    brb_array[0].sensor_imagery = c_gsfSensorImagery()

    time_series = c_gsfTimeSeriesIntensity * 1
    brb_array[0].time_series = time_series()

    """
    class c_gsfTimeSeriesIntensity(Structure):
    _fields_ = [
        ("sample_count", c_ushort),
        ("detect_sample", c_ushort),
        ("start_range_samples", c_ushort),
        ("spare", TIME_SERIES_INTENSITY_SPARE_BYTES),
        ("samples", POINTER(c_uint)),
    ]
    """
    brb_array[0].time_series[0].sample_count = len(json_row['sample_data'])
    brb_array[0].time_series[0].detect_sample = 0 # TODO: Do we need to set this?
    brb_array[0].time_series[0].start_range_samples = 0 # TODO: Do we need to set this?
    brb_array[0].time_series[0].samples = (c_uint * len(json_row['sample_data']))(*json_row['sample_data'])

    record.mb_ping.brb_inten = brb_array

    gsf_file.write(record, RecordType.GSF_RECORD_SWATH_BATHYMETRY_PING)

Howver without much luck. I read the gsf_spec and on figure 4-7 they mention a subrecord identifier, however browsing through the code I couldn't find a way to set this field.

I'd appreciate any hints you might have to move this forward, I'm also happy to provide more context if needed.