Dark object subtraction method (Chavez, 1996)(COST â. Cosine of ... COST. Desert. App. R e fle cta nce. Apparent. COST. Desert. Rayleigh. Band 7. Band 3.
Predictive Soil Mapping in Arizona’s Basin and Range Province Matt Levi1, Craig Rasmussen1, and Nathan Starman2 1Soil,
Water, and Environmental Science Department, University of Arizona 2USDA – Natural Resources Conservation Service (Phoenix, Arizona)
Outline
Introduction
Objectives Methods Results
Soil pre-mapping Atmospheric correction methods
Atmospheric effects Pre-maps
Conclusions
Introduction
The National Cooperative Soil Survey is near completion of initial mapping in the contiguous U.S. Areas of the West are still without soil information Updates planned for older surveys
Soil pre-mapping
Requires time, energy, money, and experience Surface reflectance (e.g., Landsat) is often used for developing pre-maps subject to atmospheric interactions!
Several methods of correcting for scattering and absorption effects
Assumptions
Dark object subtraction (COST)
Radiative transfer code approach (6S)
True dark object Multiple dark objects needed Must know input parameters (AOD) More complex
First goal should be to do no harm!
Objective
Objectives are to compare two methods of atmospheric correction for a Landsat 7 ETM+ image taken in a semi-arid ecosystem (~160,000 ha, Graham County, AZ).
Methods
LS scene from 12 Sept. 2000
Radiometric corrections according to LS 7 Handbook (apparent reflectance)
Correction methods
Dark object subtraction method (Chavez, 1996)(COST – Cosine of solar zenith angle) Radiative transfer code approach (6S –Second Simulation of a Satellite Signal in the Solar System)
Rayleigh scattering – scattering of light by particles smaller than wavelength Mid-Latitude / Desert atmosphere/aerosol (AERONET – Tucson)
Study Area
Landsat 7 ETM+ Data
http://ls7pm3.gsfc.nasa.gov/mainpage.html
Results - Landsat Reflectance
Band 3
COST App
Desert
Rayleigh
Band 7 Reflectance
Apparent
Apparent
COST
Desert
Rayleigh
• 36 points – – – –
Water Vegetation Geology Soil
Results 0.30
Band 1 Surface Reflectance
Surface Reflectance
0.25 0.20 0.15 0.10 0.05
Band 2
0.25 0.20 0.15 0.10 0.05 0.00
0.00 0.00
0.05
0.10
0.15
0.20
0.00
0.25
0.05
0.10 0.15 0.20 Apparent Reflectance
0.25
0.30
Apparent Reflectance 0.60
Band 3
0.30
Band 4
0.50 Surface Reflectance
Surface Reflectance
0.35
0.25 0.20 0.15 0.10 0.05
0.40 0.30 0.20 0.10 0.00
0.00 0.00
0.05
0.10
0.15
0.20
0.25
Apparent Reflectance
0.30
0.35
0.00
0.10
0.20
0.30
Apparent Reflectance
0.40
0.50
0.60
Results 0.50
0.60
Band 5
0.50
Band 7 0.40
0.30 0.20 0.10 0.00 0.00
0.20
0.40
Apparent Reflectance
0.60
Surface Reflectance
Surface Reflectance
0.40 0.30 0.20 0.10 0.00 0.00
0.10
0.20
Apparent Reflectance
0.30
0.40
Results – Soil Pre-map
1:63,000 Scale
1:24,000 Scale
Summary
More variation in COST model As wavelength increases, COST model overestimates reflectance Rayleigh scattering had best relationship with apparent reflectance Lack of ground data for the date of scene inhibits correction methods No true dark objects
Conclusions
Application of the surface reflectance will determine the complexity and necessary assumptions of the atmospheric correction needed. Available data (atmosphere / aerosol) will also direct correction method. For soil survey purposes, a Rayleigh correction is suggested when atmospheric conditions cannot be quantified.
Future Mapping Focus
1:63,000 Scale
1:24,000 Scale
References
Chavez, P.S. 1996. Image-based atmospheric corrections – revisited and improved. Photogram. Engineer. Rem. Sens. 62:1025-1036. Vermote, E.F., D. Tanré, J.L. Deuzé, M. Herman, and J. Morcrette. 1997. Second simulation of the satellite signal in the solar spectrum, 6S: an overview. IEEE Trans. Geosci. Remote Sensing. 35: 675-686. http://modis-sr.ltdri.org/code.html http://aeronet.gsfc.nasa.gov/cgibin/type_one_station_opera_v2_new?site=Tucson&nach al=2&level=1&place_code=10
Thank You!
Results Stdev Band 1 2 3 4 5 7
Apparent Mid-lat Reflectance COST Rayleigh Desert 0.014 0.018 0.016 0.017 0.023 0.027 0.024 0.027 0.039 0.048 0.040 0.044 0.040 0.049 0.040 0.043 0.072 0.090 0.072 0.075 0.066 0.085 0.066 0.073
1.00
NDVI
Surface Reflectance
0.80
0.60 cost mid-desert 0.40
rayleigh 11 Linear (1 1)
0.20
0.00 -0.20 -0.20
0.00
0.20
0.40
Apparent Reflectance
0.60
0.80
1.00
Results Reflectance
Band 1
COST App a
Desert
Rayleigh
Band 2 Reflectance
Apparent
Apparent
COST App
Desert
Rayleigh
Reflectance
Band 3
COST App a
Desert
Rayleigh
Band 4
Reflectance
Apparent
Apparent
COST App a
Desert
Rayleigh
Reflectance
Band 5
COST App a
Desert
Rayleigh
Band 7 Reflectance
Apparent
Apparent
COST App a
Desert
Rayleigh
