International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
study used wild spectroradiometer ISI921VF for wild spectral 
measurements; the band range, which is fitted within the band 
range of SPOT-5 satellite through spectral resampling, is 
380~1050nm of visible light and near infrared light. 
  
  
  
  
  
Band Wavelength Range(um) 
Panchromatic 0.48~0.71 
B1(Green) 0.50~0.59 
B2(Red) 0.61~0.68 
B3(Near infrared) 0.78~0.89 
B4(Short wave infrared) 1.58~1.75 
  
Table 1. Bands and wavelength range of SPOT-5 satellite 
Before the atmospheric correction, first make the geometric 
correction on the SPOT-5 image by using the coordinate data of 
the known control point, and then transform the DN value of 
i : : —2 -l -l 
SPOT-5 into radiance (Unit: uw-em ^ :nm -sr ) and 
apparent reflectance. The transformation process can be 
finished through the Modeler of ERDAS IMAGINE? 2. 
3. ANALYSIS OF APPLICATION AND EFFECT OF 
ATMOSPHERIC CORRECTION 
3.1 Model FLAASH atmospheric correction 
FLASSH is developed by both Spectral Science, Inc. (SSI), the 
leader of the research on atmospheric correction algorithm, and 
Air Force Research Labs(AFRL). It combines radioactive 
transfer code of MODTRAN4+ and has been modified on this 
basis. FLAASH is the tool for first-principle atmospheric 
correction, which is able to correct from the visible light, near 
infrared light to shortwave infrared light and can also eliminate 
most of the influence which the air and light and other factors 
have on clutter reflectance to obtain more accurate parameters 
of reflectivity, emissivity, surface temperature and other real 
physical models of surface features. 
FLAASH begins with a standard equation of spectral radiance 
of the single pixel received by a standard planar lambertian (or 
nearly a planar lambertian), which is based on the sun spectrum 
(not including thermal radiation), by the sensor. 
| A B : 
Lebe i. (1) 
1-554 das 
Thereinto, L’ is the radiance for the single pixel received by the 
sensor; P is the surface reflectance for the pixel; pis the 
average surface reflectance for this pixel and surrounding 
pixels; S is the spherical albedo for the atmosphere; L,’ is the 
radiance when atmosphere radiation enters into the sensor, 
A,B is the coefficient determined by the atmospheric conditions 
and the geometric conditions of underlying surface with 
nothing to do with surface reflectance. 
(A 9 /(1- e , S)) indicates the radiation energy entering into the 
sensor directly from the target surface features, which implies 
two cases: the reflection happening when the sun irradiates on 
the target surface features; the neighboring surface features 
scatter through the atmosphere and then irradiate on the surface 
features for reflection again U (Bo J(1-o, S)) indicates the 
amount of radiation which enters into the sensor through the 
  
  
atmosphere from the surface. The difference between P and 
P , explains "proximity effect" (mixed radiation close to pixel) 
caused by the atmospheric scattering, in order to ignore this 
proximity effect, so p _p .. However, there will be significant 
errors when there is mist or a strong contrast between the 
surfaces. 
According to the Formula (1), surface reflectance can be 
calculated pixel by pixel. FLAASH uses spatial average 
radiancy, ignoring the “proximity effect”, to get approximate 
equation (2) and to estimate the spatial average reflectance. 
Thereinto, L, is the spatial average radiation image generated 
by convolution with the radiation image and spatial weighting 
function. 
B 
, [8:2 2). Q) 
1-p 3S 
Most of the atmospheric correction parameters used in this trial 
are from the header file of image data, and the specific 
parameter data is shown in Table 2. After obtaining the required 
parameter, the true surface reflectance of the whole image can 
be calculated pixel by pixel by using Equation 1 and Equation 
2. 
  
  
  
  
  
  
  
  
  
Date of Time of Height of 
; ; Sensor 
Imaging Imaging Sensor 
2010.11.2 3:28:14 SPOT-5 800km 
Atmospheric ^ Aerosol Center Center 
Model Type Longitude/(^ ) Latitude/(^ ) 
MLW Rural 113.1001 28.0001 
Elevation Angle of ~~ Azimuth of the : bay 
the Sun/(° ) Sun/(° ) Altitude — Visibility 
46.192779 164.892501 0.037km 35km 
  
Note: Imaging time is GMT with a difference of 8 hours 
between GMT and Beijing Time. 
Table 2. Input parameters of FLAASH atmospheric 
correction 
3.2 Model QUAC atmospheric correction 
Model QUAC is the method of atmospheric correction for 
hyper spectral and multispectral images from the visible light, 
near infrared light to shout-wave infrared light. QUAC is 
different from the first-principle atmospheric correction, 
because it obtains atmospheric compensating parameters 
directly from the image (observe pixel spectral) without 
complete information to achieve the atmospheric correction 
more approximate than FLAASH. 
p =(p,+p,+—+p,)/n (3) 
As shown in Equation (3) below, QUAC is based on experience 
to collect the average reflectance of different substances, such 
as the end member spectrum in the field of vision. n indicates 
the number of end members, essentially independent field of 
vision, which means a faster operating rate than the