You are using an outdated browser that does not fully support the intranda viewer.
As a result, some pages may not be displayed correctly.

We recommend you use one of the following browsers:

Full text

Mapping without the sun
Zhang, Jixian

In the research of Munechika et al. (1993), simulated
synthesized panchromatic images are calculated by method
proposed by Suits et al. (1988):
Pan Lsyn=Y. ( Pi XS Li (2)
To obtain parameter^?., Munechika et al. (1993) adopted an
improved atmospheric model to modify received object
reflection and relative spectral response, and to measure 5
representative reflection spectrum of land cover, including city,
soil, water, tree and grass, cp, can be obtained through
regression analysis calculation of 5 types actual measure value
and value from atmospheric model. After get Pan Uvn ,
panchromatic images are processed histogram matching with
simulated synthesized images to eliminate difference between
atmospheric and radiation.
Pan H . panchromatic image, not only with band 1, 2, 3, 4 of
TM image, which can avoid TM image colour distortion.
2.3 SSVR Method
There still exist some problems of SVR improved by Zhang
(1999) and Zhang (2001). Firstly, according to the improvement,
the less correlation lies, the more spectral information can be
reserved, and the accuracy of regression coefficient which is
calculated through regression analysis method is doubtful.
Secondly, numerous pixels with different types of land cover
which is selected randomly should be added to regression
analysis, so that more experiences are needed. Thirdly,
parameters obtained from regression analysis have no physical
meaning and cannot be explained, on the same time, the
Simplified Synthetic Variable Ratio (SSVR) is presented.
2.2 SVR Method improved by Zhang
Zhang (1999) and Zhang (2001) suggest that it is difficult to get
parameter (p. in SVR method of Munechika et al.( 1993), and
only several specific land cover types are used. For one thing,
this method is not practical in regular large area fusion. For
another thing, 5 types land cover cannot be representative in a
large area, and cannot assure that spectra properties of other
types land cover can be recorded. Furthermore, SPOT
panchromatic images should be processed histogram matching,
as Pan Lsvn in equation (2) can be obtained through certain
atmosphere and specific land cover type.
In view of above problems, Zhang (1999) and Zhang (2001)
modified SVR method in this way:
XSP, = Pan
here, XSP i and Pan H remain the same meaning as in equation
(!)• XS H means band i grey value after resampling
multispectral images to the same pixel size with panchromatic
images. p a n Hsyn means grey value of high spatial resolution
image which is synthesized in the way shows in below equation:
Pan Hsyn ='Z ( P‘ XS h, ( 4 )
Equation (5) is used to calculate parameter q>. which can be
obtained through regression analysis calculation of 5 original
PAN images and original MS images XS Hi (has the same pixel
size with Pan H )•
Pan h =Yu ( Pi XS m ( 5 )
The core problems of SVR and its modified method are
simulated from low spatial resolution multiple bands to low
spatial resolution panchromatic bands. The SSVR method doing
the simplification is based on some rules: assuming Pan images
have the same spectrum range with MS images, which is one of
the hypothesis of ISVR, the Pan energy simulated through low
resolution MS images can be approximately substituted by the
energy of the sampled high resolution Pan images, that
is e « E
^ Pan ^ ~ ^ Pan L
The equation of SVR could be expressed as
XSP, = Pan,
V P Pan
where XSP, is radiance value of band i of the high resolution
images after fusion, Pan H is the radiance value of original
high resolution Pan images, E i s the i band radiance value
of the original low resolution multispectral images, E Pan is
radiance value resampled from high resolution Pan images, and
represents the energy ratio should be converted from
V Pan i 2
low resolution to high resolution on account of the
correspondence among pixels between high resolution images
and low resolution images. Pan H denotes the spatial
information of fused images, and spectral information is
embodied in the form of
"i 2
Mean value method is adopted resampled from E to E
P an h p an L
L-t pan h
Improvements of SVR method by Zhang include: more stable
parameter (p. , easier acquisition of parameter (p., and the merit
that in fusion process, every band can be synthesized with
where N denotes the pixel amount of low resolution
corresponding to high resolution. If Pan L and E pan are
corresponded to Figure 2-a and Figure 2-b respectively, then