Jan 10, 2003
Some MODIS products and pre-processing
Hongjie Xie
New Mexico Tech
hjxie@nmt.edu
Introduction
The MODIS/Terra data products have two different datasets available for
downloading: MODIS L1B (geolocation and radiometric calibrated data, through
http://daac.gsfc.nasa.gov/data/dataset/MODIS/01_Level_1/03_Cal_Rad_1km/index.html)
,
and
MODIS
geophysics
products
(L2,
L3
and
L4
through
http://edcimswww.cr.usgs.gov/pub/imswelcome/). Here I am introducing the difference
of these two datasets and using datasets of June 16, 2002 as an example. I concluded that
it is difficult to directly use the MODIS data or products for our ET estimates using
SEBAL algorithm even with lots of following pre-processing.
1
MODIS L1B dataset
MODIS L1B dataset is daily data (two images for each day: day time and night
time images) with 36 bands (actually 38 images because bands 13 and 14 have both low
and high gain images). For our purpose, I only downloaded the day time and 1km
resolution bands, which is from band 8 to band 36. Of them, bands 8, 9, 10, 11, 12, 13lo,
13 hi, 14lo, 14hi, 15, 16, 17, 18, 19, and 26 are reflective solar bands
(GSUB1.A2002167.1755.003.2002351204005.hdf), while 20- 25 and 27-36 are emissive
bands (GSUB1.A2002167.1755.003.2002353195012.hdf). Using the ENVI 3.6 or Erdas
IMAGINE 8.6 can import and georeference to a particular projection that users want.
Pixel numbers of these images are scaled integers. The equation for transferring the
scaled integers into reflectance or radiance is scale *(scaled integer-offset). The bellows
are the bands and related scales and offsets (can be obtained by using a free software
called HDFLook):
band_names: 8,9,10,11,12,13lo,13hi,14lo,14hi,15,16,17,18,19,26
radiance_scales:
0.00795877 0.00492686 0.00363404 0.00281856 0.00224682
0.00112017 0.000833487 0.00110254 0.000614436 0.000929919 0.000895564
0.00663277 0.00907252 0.00660929 0.00289308
radiance_offsets:
316.972 316.972 316.972 316.972 316.972 316.972
316.972 316.972 316.972 316.972 316.972 316.972 316.972 316.972 316.972
radiance_units:
Watts/m^2/micrometer/steradian
reflectance_scales: 1.47881e-05 8.39465e-06 5.95066e-06 4.85232e-06
3.85158e-06 2.34699e-06 1.74632e-06 2.37137e-06 1.32155e-06 2.32964e-06
2.98559e-06 2.30157e-05 3.36832e-05 2.45521e-05 2.57143e-05
reflectance_offsets: 316.972 316.972 316.972 316.972 316.972 316.972
316.972 316.972 316.972 316.972 316.972 316.972 316.972 316.972 316.972
reflectance_units: none
band_names: 20,21,22,23,24,25,27,28,29,30,31,32,33,34,35,36
radiance_scales:
6.2624e-05 0.00314951 6.9216e-05 7.9104e-05 3.15561e-05
5.63982e-05 0.000117557 0.00019245 0.000532487 0.000406323 0.000840022
0.000729698 0.000262264 0.000200696 0.000176708 0.000118339
radiance_offsets:
2730.58 2730.58 2730.58 2730.58 1077.44 1560.33
2730.58 2317.49 2730.58 1560.33 1577.34 1658.22 2501.3 2501.3 2501.3
2501.3
radiance_units:
Watts/m^2/micrometer/steradian
Dataset files:
1. g167b8-36refl-radi.img (the image with 31 layers after transferred g167b836.img: scaled integers into reflectance or radiance using the above equation and
parameters)
2
MODIS geophysical products
MODIS geophysical products derived from L1B daily data, but mostly in 8, 16 or 96
days composite data. For our purpose, I downloaded 6 different series of datasets:







MODIS/TERRA ALBEDO 16-DAY L3 GLOBAL 1KM ISIN GRID V003 (MOD43B3)
MODIS/TERRA BRDF/ALBEDO MODEL-1 16-DAY L3 GLOBAL 1 KM ISIN GRID V003
(MOD43B1)
MODIS/TERRA LAND COVER TYPE 96-DAY L3 GLOBAL 1KM ISIN GRID V003
(MOD12)
MODIS/TERRA LAND SURFACE TEMPERATURE/EMISSIVITY DAILY L3 GLOBAL
1KM ISIN GRID V003 (MOD11)
MODIS/TERRA LEAF AREA INDEX/FPAR 8-DAY L4 GLOBAL 1KM ISIN GRID V003
(MOD15)
MODIS/TERRA SURFACE REFLECTANCE DAILY L2G GLOBAL 500M ISIN GRID V003
(MOD09)
MODIS/TERRA VEGETATION INDICES 16-DAY L3 GLOBAL 1KM ISIN GRID V003
(MOD13)
Two MODIS granules (0805 and 0905) cover the state of New Mexico. I used the
MODIS’s reprojection tool (MRT, free software) to mosaic two granules and reproject it
to UTM zone 13 and WGS84 coordinate system. And HDFLook tool was used to obtain
the related scale and offset for each file.
2.1
Two types of 16-day albedo: white sky and black sky (local solar noon), are
provided. Each includes 10 bands, which are derived in seven spectral bands, as well as
in the visible (0.3-0.7), the near/mid-infrared (0.7-5.0) and the total shortwave (0.3-5.0)
broadbands. From the scaled integer to albedo using the equation: scaled integer * 0.001.
Datasets:
2. m_16day_wsky_albedo.img (10 layers)
3. m_16day_bsky_albedo.img (10 layers)
2.2
Land cover type 1 is specified into 16 classes as:
water 0
evergreen needleleaf forest 1
evergreen broadleaf forest 2
deciduous needleleaf forest 3
deciduous broadleaf forest 4
mixed forests 5
closed shrubland 6
open shrubland 7
woody savannas 8
savannas 9
grasslands 10
permanent wetlands 11
croplands 12
urban and built-up 13
cropland/natural vegetation mosaic 14
snow and ice 15
barren or sparsely vegetated 16
unclassified 254
Dataset:
4. m_landcover.tif
2.3
Temperature including daily day-time and night-time temperatures. And
emissivity is the average of the emissivity band 31 and band 32. From the scaled integer
to temperature and emissivity using equations: scaled integer *0.002+0.49 for emissivity,
and scaled integer *0.02 for temperature.
Datasets:
5. m_daily_temperture.img (layer 1: day-time, layer 2: night-time)
6. m_daily_emissivity.img (averaging the bands 31 and 32)
2.4
Leaf area index equal to scaled integer * 0.1
Datasets:
7. m_8day_lai.img
2.5
Surface reflectance includes the MODIS bands 1-7, and resample to 1 km for our
purpose. The equation is scaled integer * 0.0001.
Datasets:
8. m_daily_reflectance.img
2.6 Vegetation index equals to scaled integer * 0.0001
Datasets:
9. m_16day_ndvi.img