This function requires a TeraScan MODIS license.
modis_bt [ parameter=value ... ] [ inputfile outputfile ] modis_bt [ parameter=value ... ] [ inputfile ... directory ]
Parameters are var_names, channels, add_b_suffix.
modis_bt corrects for the panoramic bowtie effect due to the behavior of the MODIS sensor cross-track scanning mirror. This effect leads to a scan-to-scan overlap of pixels at scan angles greater than 25 degrees. The scan gap at nadir is nominally zero. modis_bt corrects calibrated data output by IMAPP.
modis_bt can be used to correct any data in original MODIS sensor coordinates, provided that the data is 1000m, 500m or 250m resolution, and that the data is stored as short integers.
There are two ways to specify the channels to bowtie-correct: (1) a list of variable names, or (2) a list of channel numbers. If variable names are supplied, channel numbers are not used. Channel numbers refer to the 36 MODIS channel numbers. The MODIS channel number 'n' is assumed to correspond to the variable name modis_chn.
After correction, if add_b_suffix=yes, the letter 'b' is appended to only those variables with names matching modis_chn.OPTIONAL. List of variables to bowtie-correct. Name wildcards are allowed. There is no default. If a list of variable names is not supplied, a list of channel numbers will be used instead.
This is a list of the MODIS channels to extract from the PDS data set. The 36 channels correspond to the following MODIS channels:
Channels 1 & 2 correspond to bandwidths 620-670 and 841-876 nm @250 m resolution.
Channels 3-7 correspond to bandwidths 459-479, 545-565, 1230-1250, 1628-1652, and 2105-2155 nm @500 m resolution.
Channels 8-19 correspond to the reflective and Near IR bandwidths 405-420, 438-448, 483-493, 526-536, 546-556, 662-672, 673-683, 743-753, 862-877, 890-920, 931-941 and 915-965 nm @1000 m resolution.
Channels 20-36 correspond to the emissive bandwidths 3.66-3.84, 3.92-3.98, 3.92-3.98, 4.02-4.08, 4.43-4.49, 4.48-4.54, 1.36-1.39, 6.535-6.89, 7.17-7.47, 8.40-8.70, 9.58-9.88, 10.78-11.28, 11.77-12.27, 13.18-13.48, 13.48-13.78, 13.78-14.08, 14.08-14.38 micrometers @1000 m resolution.
Valid responses are [1 through 36]. There is no default. Specify 1^36 if all 36 channels need to be corrected.
Channels 13 and 14 have both high and low signal-to-noise ratios. IMAPP extracts both and creates a separate variable for each in the output dataset: modis_ch13H, modis_ch13L, modis_ch14H, and modis_ch14L. When you correct channel 13 or 14, you get both the high and low variables for each.
OPTIONAL. Specifies whether or not to append the letter 'b' to variables named modis_chn after bowtie-correction.
Valid responses are [ yes or no ]. The default is yes.
Create a MODIS calibrated TeraScan dataset named t1.00306.1557.RADIANCE_bt corrected for the bowtie effect for channels 1, 3, and 4 output from IMAPP.
scrum% modis_bt in/out files : char(255) ? t1.00306.1557.RADIANCE_tdf t1.00306.1557.RADIANCE_bt channels : int ( 36) ? [3 7 10 14 17 21 25 28 32 35]1 3 4 >*> modis_ch01b: Nl 19960, Ns 5416 250m Channel: 01(00) - Line 0 250m Channel: 01(00) - Line 200 250m Channel: 01(00) - Line 400 >*> modis_ch03b: Nl 9980, Ns 2708 500m Channel: 03(00) - Line 0 500m Channel: 03(00) - Line 100 500m Channel: 03(00) - Line 200 500m Channel: 03(00) - Line 300 >*> modis_ch04b: Nl 9980, Ns 2708 500m Channel: 04(00) - Line 0 500m Channel: 04(00) - Line 100 500m Channel: 04(00) - Line 200 500m Channel: 04(00) - Line 300
IMAPP, modis_color, mod_chlor, modis_turbidity, MODIS overview, Creating calibrated MODIS datasets
MODIS Level 1A Earth Location: Algorithm Theoretical Basis Document Ver. 3.0. SDST-092. GSFC SBRS. Aug 26, 1997.
Last Update: $Date: 2002/05/07 23:22:46 $