UDF NDTI index is different from default NDTI

[Azarozo19]

I am currently comparing the NDTI index from the UDF vs the default (No UDF). The parameters used for the default process are INDEX = NDTI, SENSORS = SEN2A SEN2B, DATE_RANGE = 2021-01-01 2021-12-31. The output is nDates = 22 with spectral and nodata values.
The UDF parameter file has the same settings. In the new function script the outarray output from the function forcepy_pixels has different amounts of bands per pixel and the values differ as well. Is it possible to debug it efficiently? Does someone have an idea why the nBands are so different?

`start = date.fromisoformat('1970-01-01')

def forcepy_init(dates, sensors, bandnames):
"""
dates: numpy.ndarraynDates days since epoch (1970-01-01)
sensors: numpy.ndarraynDates
bandnames: numpy.ndarraynBands
"""

return [f'{(start+timedelta(days=int(dat))).year}{(start+timedelta(days=int(dat))).month:02d}{(start+timedelta(days=int(dat))).day:02d}_{sens.decode("utf-8")}' for dat, sens in zip(dates, sensors)]

def forcepy_pixel(inarray, outarray, dates, sensors, bandnames, nodata, nproc):
"""
inarray: numpy.ndarraynDates, nBands, nrows, ncols
outarray: numpy.ndarraynOutBands initialized with no data values
dates: numpy.ndarraynDates days since epoch (1970-01-01)
sensors: numpy.ndarraynDates
bandnames: numpy.ndarraynBands
nodata: int
nproc: number of allowed processes/threads
Write results into outarray.
"""

inarray = inarray.astype(np.float32)
inarray = inarray[:, :, 0, 0]
invalid = inarray == nodata  ## bool mask values

valid = np.where(inarray[:, 0] != nodata)[0]  # skip no data; just check first band

if len(valid) == 0:
    return
inarray[invalid] = np.nan

swir1 = np.argwhere(bandnames == b'SWIR1')[0][0]
swir2 = np.argwhere(bandnames == b'SWIR2')[0][0]

vals = inarray[valid, :]

ndti = (vals[:, swir1] - vals[:, swir2]) / (vals[:, swir1] + vals[:, swir2])

outarray[valid] = ndti*10000

`

[davidfrantz]

Dear @Azarozo19,

it is difficult to say without seeing the parameter files. I assume, though, that you used interpolation in the TSA submodule (default), whereas the UDF submodule has no such option.

Best,
David