RETRIEVING BRDF OF DESERT USING TIME SERIES OF MODIS IMAGERY
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Transcript of RETRIEVING BRDF OF DESERT USING TIME SERIES OF MODIS IMAGERY
RETRIEVING BRDF OF DESERT USING TIME SERIES OF MODIS IMAGERY
Haixia Huang, Bo Zhong, Qinhuo Liu, and Lin SunPresented by Bo [email protected]
Institute of Remote Sensing Applications, Chinese Academy of Sciences
IGRSS 2011, Vancouver , Canda
Outline
Background
Methodology
Preliminary results
Applicatoins
Conclusions
Background
BRDF is the key parameter for:Quantitative remote sensingErath radiation budgetMore
Desert is one of the main landcover typesStrongly reflecting the solar radiationMore
Problem
• There is no “good” BRDF product of desert
Methodology-flowchartMODIS imagery
Converting DN to TOA reflectance
Identifying the “clearest” of each observations
Retrieving reflectance of “clearest” observations
Fitting to Staylor-Suttles BRDF model
Lookup Tables
BRDF of desert
Methodology- site choosing
Location of the experimental site(MODIS imagery color
composite)
Cole view of the site(TM imagery color composite)
Methodology- site choosing
It is stable, so it can be seen as an invariant
object;
There are a lot of lakes within the calibration
site, which are seldom polluted, so the lowest
AOD of calibration site can be determined by
Dark Object (DO) method using Landsat TM and
ETM+ data.
8
( a)Mar. 3, 2000 ( b) Feb. 3, 2010
Methodology- site choosing
AOD retrieval using DO method
40 60 80 1000
1
2
3
Aer
osol
opt
ical dep
th
Apparent radiance(w/m2/sr/mic)
Aerosol optical depth and radiance curveCorresponding path radiance and aerosol optical depth
52.87
0.43
ETM+
imaging
date
Aerosol
optical
depth
TM
imaging
date
Aerosol
optical
depth
2000.03.03 0.1543 2006.09.20 0
2000.04.29 0 2006.10.31 0.0440
2001.10.16 0.0218 2007.05.18 0.1536
2001.11.17 0 2007.06.03 0
2002.01.04 0.0657 2009.06.17 0.4279
2002.03.18 0.2801 2009.08.11 0.05444
2002.05.28 0.3274 2009.08.27 0.0043
2002.09.17 0.1058 2009.09.28 0.0096
2002.11.04 0.3633 2010.02.03 0.07676
2002.11.13 0.0286 2010.06.04 0.254
2002.12.15 0.1195 2010.07.29 0.3552
2003.03.28 0.4273 2010.08.14 0
2010.08.23 0.2178
Original methodTime series of MODIS imagery
Identifying clear pixels
Reflectance of clear pixels
BRDF fitting
Reflectance of hazy pixels
AOD of hazy pixels
LUT
MODIS surface reflectance
Modifications for the original method
AOD determination for the “clearest” days;
Shrinking the use of the algorithm from globe to the desert
calibration site, which is stable;
Identifying the “clearest” observations for every 10 degrees
in view zenith angles from 0-50 degree (0-10, 11-20, 21-30,
31-40, and 41-50);
Using Staylor-Suttles BRDF model instead of Walthall BRDF.
MODIS-B3: Staylor-Suttles coefficients
Preliminary results
MODIS-B1: Staylor-Suttles coefficients
MODIS-B2: Staylor-Suttles coefficients
Comparison with MODIS products
R2 much
higher RMSE is
lower
Applications I: inter-calibration of AVHRR using retrieve BRDF
Spectral matching of AVHRR and MODIS
AVHRR data simulation using the new method
Inter-calibration
Validation
Spectral matching
AVHRR 1 (0.645 μm)
AVHRR 2 (0.865 μm)
AVHRR 3 (1.6 μm)
ai 0.9885 1.0105 1.0004
Applications II: global desert BRDF retrieval
Mapping of the desert
BRDF and AOD retrieval simultaneously using
the new method
Preliminary validation
The chosen desert sites
The geolocations of the deserts
Desert Name
Lat( °) Lon( °) Altitude( m)
Duration(yyyy.mm.d
)Taklimak
an39.0°N-40°N 84°E-85°E 1050 2009.10.1-
210.10.1
Rabal-Khali
18.8°N-19.8°N 45.5°E-46.5°E 700 2009.10.1-210.10.1
Lybia 24°N-25°N 12°E-13°E 740 2009.10.1-210.10.1
Sahara 19.5°N-20.5°N 8°W-9°W 260 2009.10.1-210.10.1
Taklimakan desert
Rabal-Khali desert
Lybia desert
Sahara desert
Conclusions
The new method is able to catch the BRDF
characterization of deserts
This method can be used for inter-calibration of
reflective bands of moderate satellite data like
AVHRR
This method is helpful for researches on earth
radiation budget
Thank you for your attention!