## 4 Experiments and Results  
### Pseudo-TCT of GF-2  
From Table 1 it can be seen that the sensor parameters of GF-2 and IKONOS are highly similar, so the TCT coefficients of IKONOS are used directly for GF-2. From the paper \"A Tasseled Cap Transformation for IKONOS Images\" we know R as follows:  
\[\mathrm{R}= \begin{bmatrix}0.326&-0.311&-0.612&-0.650\\ 0.509&-0.356&-0.312&0.719\\ 0.560&-0.325&0.722&-0.243\\ 0.567&0.819&-0.081&-0.031\end{bmatrix}  \tag{6}\]  
To avoid negative grey values after pseudo-TCT, each band of the pseudo-TCT image was linearly stretched to [0, 65,535], since the GF-2 image is a 16-bit image. Since the original image has fewer values at the ends of the grey histogram, the overall image perception is still dark after linear stretching. Therefore, the image was then stretched with a percentage truncation, with a minimum and maximum exclusion ratio of 10% and a stretching range \begin{table}
\begin{tabular}{c c c c} \hline
**Main Parameters** & **Spectra** & **GF-2** & **IKONOS** \\ \hline Type of orbit & & Regression Sun-synchronous orbit & Sun-synchronous orbit \\ Orbit height & & 631 km & 681 km \\ Orbital inclination & & 97.9080\({}^{\circ}\) & 98.1\({}^{\circ}\) \\ Spectral range & Panchromatic & 0.45–0.90 μm & 0.45–0.90 μm \\  & Multispectral & 0.45–0.52 μm & 0.45–0.53 μm \\  & & 0.52–0.59 μm & 0.52–0.61 μm \\  & & 0.63–0.69 μm & 0.64–0.72 μm \\  & & 0.77–0.89 μm & 0.77–0.88 μm \\ Spatial resolution & Panchromatic & 0.8 μm (1 m after orthorectification) & 1 m \\  & Multispectral & 3.2 m (4 m after orthorectification) & 4 m \\ \hline \end{tabular}
\end{table} 
Table 1: Main parameters of GF-2 and IKONOS. of [0, 255]. The grey value corresponding to 10% and the grey value corresponding to 90% of each band were calculated, and the two values were regarded as the minimum and maximum of the grey values of the corresponding band, and the grey values located between 10% and 90% was linearly stretched to [0, 255], and the grey values smaller than the minimum was directly assigned to 0, and the grey values larger than the maximum was assigned to 255. Since each band of the pseudo-TCT image no longer has the physical meaning of each band of the TCT image, it is not necessary to calculate the pseudo-TCT according to the original band order of the TCT, and the four bands can be arranged and combined to obtain 24 pseudo-TCT combinations. For the convenience of description, the blue band is 0, the green band is 1, the red band is 2 and the NIR band is 3. For example, the 0123 combination is as follows:  
\[\mathrm{u_{1}}=0.326\mathrm{x_{0}}\ -\ 0.311\mathrm{x_{1}}-\ 0.612\mathrm{x_{2}}\ - \ 0.650\mathrm{x_{3}} \tag{7}\]  
\[\mathrm{u_{2}}=0.509\mathrm{x_{0}}\ -\ 0.356\mathrm{x_{1}}\ -\ 0.312\mathrm{x_{2}}\ + 0.719\mathrm{x_{3}} \tag{8}\]  
\[\mathrm{u_{3}}\ =0.560\mathrm{x_{0}}\ -\ 0.325\mathrm{x_{1}}\ +0.722\mathrm{x_{2}} -\ 0.243\mathrm{x_{3}} \tag{9}\]  
\[\mathrm{u_{4}}=0.567\mathrm{x_{0}}\ +0.819\mathrm{x_{1}}\ -\ 0.081\mathrm{x_{2}}\ - \ 0.031\mathrm{x_{3}} \tag{10}\]  
where \(\mathrm{u_{1}}\), \(\mathrm{u_{2}}\), \(\mathrm{u_{3}}\) and \(\mathrm{u_{4}}\) denote the bands of the pseudo-TCT, and \(\mathrm{x_{0}}\), \(\mathrm{x_{1}}\), \(\mathrm{x_{2}}\) and \(\mathrm{x_{3}}\) denote the blue band, green band, red band and near-infrared band, respectively. Region 2, region 3 and region 4, which are rich in types of ground objects and relatively representative, were selected to demonstrate the visual effect of the pseudo-TCT. The original images, TCT images and a portion of the corresponding pseudo-TCT images are shown in Figure 3.  
Figure 3: _Cont._  
It can be seen from Figure 3 that the visual effect of the images is improved in both the 0123 combination images and the TCT images relative to the original images. It can also be seen from Figure 3 that shadows and water bodies are relatively similar in the images, which is consistent with other image segmentation studies that shadows and water bodies are easily confused.