def create_dispersion_from_ascii(l1b_file, out_disp_file, disp_in_file, sounding_id=None, index_scheme=None):
asc_l1b_obj = OCO_Matrix(l1b_file)
if sounding_id == None:
sounding_id = asc_l1b_obj.header['sounding_id']
if disp_in_file == None:
raise IOError('No dispersion file specified')
latitude = float(asc_l1b_obj.header['sounding_latitude'].split()[0])
sza_r = math.radians(float(asc_l1b_obj.header['sounding_solar_zenith'].split()[0]))
saz_r = math.radians(float(asc_l1b_obj.header['sounding_solar_azimuth'].split()[0]))
time_stamp = asc_l1b_obj.header['frame_time_stamp']
time_struct = OCO_TextUtils.convert_timestamp_to_struct(time_stamp)
pixel_ranges = asc_l1b_obj.pixel_ranges()
aband_data = asc_l1b_obj['Radiance'][slice(*pixel_ranges[0]), 0]
disp_in_obj = OCO_Matrix(disp_in_file)
dispersion_coefs = disp_in_obj[DISPERSION_ASCII_COLUMN_IDENT].transpose()
create_scene_dispersion_file(sounding_id, latitude, sza_r, saz_r, time_struct, aband_data, dispersion_coefs, out_disp_file, index_scheme=index_scheme)
