GSVSoil

 1# coding: utf-8
 2# GSV soil model: it simulates soil spectra from a few parameters
 3# It is adpated from: Jiang, C., Fang, H., 2019. GSV: a general model for hyperspectral soil reflectance simulation.
 4# Int. J. Appl. Earth Obs. Geoinformation 83, 101932. https://doi.org/10.1016/j.jag.2019.101932
 5import numpy as np
 6import os
 7from typing import List, Union
 8
 9
10class GSVSoil(object):
11    """
12    GSV soil model: it simulates soil spectra from a few parameters
13    It is adpated from: Jiang, C., Fang, H., 2019. GSV: a general model for hyperspectral soil reflectance simulation.
14    Int. J. Appl. Earth Obs. Geoinformation 83, 101932. https://doi.org/10.1016/j.jag.2019.101932.
15    Code example:
16    ```
17    import matplotlib.pyplot as plt
18    gsv_model = GSVSoil()
19    for c1 in [0.3, 0.7]:
20        for c2 in [-0.1, 0]:
21            for c3 in [0, 0.05]:
22                for cSM in [-0.2, 0]:
23                    spectra = gsv_model.get_soil_spectra_gsv3(np.arange(400, 2501, 10),
24                    c1, c2, c3, cSM)
25                    plt.plot(np.arange(400, 2501, 10), spectra)
26    plt.show()
27    ```
28    """
29    def __init__(self,):
30        curr_dir = os.path.split(os.path.realpath(__file__))[0]
31        self.__GSV = np.vstack([np.loadtxt(os.path.join(curr_dir, r'data/DryVec.txt')),
32                                np.loadtxt(os.path.join(curr_dir, r'data/SMVec.txt'))])
33        # self.__WVL = np.arange(400, 2501, 10)
34
35    def get_soil_spectra_gsv3(self, wavelength: Union[List[float], np.ndarray],
36                              c1: float,
37                              c2: float,
38                              c3: float,
39                              csm: float) -> List:
40        """
41        Compute the soil reflectance with GSV soil model
42        :param wavelength: Wavelength for generating soil reflectance
43        :param c1: c1, c2, c3 are three coefficients to determine a dry soil spectrum,Usually,
44        c1 controls the brightness (not physically) of the soil, c2 and c3 control the shapes.
45        :param c2:
46        :param c3:
47        :param csm: csm determines a wet soil spectrum. They are combined to form a soil spectrum. Recommendation value
48         of csm is [-0.6, 0], 0 means no wet is considered, smaller value means more wet.
49        :return: a list with soil reflectance
50        """
51        lower_bound = np.array(list(map(lambda x: int((x-400)/10), wavelength)))
52        upper_bound = lower_bound + 1
53        upper_bound[upper_bound >= 211] = 210
54        gsv = self.__GSV[:, lower_bound]
55        spec_lower = c1*gsv[0]+c2*gsv[1]+c3*gsv[2]+csm*gsv[3]
56        gsv = self.__GSV[:, upper_bound]
57        spec_upper = c1 * gsv[0] + c2 * gsv[1] + c3 * gsv[2] + csm * gsv[3]
58        spec = list(map(lambda lr, ur, wl, lb: lr+(ur-lr)/10*(wl-lb*10-400), spec_lower, spec_upper,
59                        wavelength, lower_bound))
60        return spec
61
62    def get_soil_spectra_gsv1(self, wavelength, c1, csm):
63        """
64        Compute the soil reflectance with GSV soil model
65        :param wavelength: Wavelength for generating soil reflectance
66        :param c1: c1 the coefficient to determine a dry soil spectrum
67        :param csm: csm determines a wet soil spectrum.
68        :return: a list with soil reflectance
69        """
70        lower_bound = np.array(list(map(lambda x: int((x - 400) / 10), wavelength)))
71        upper_bound = lower_bound + 1
72        upper_bound[upper_bound >= 211] = 210
73        gsv = self.__GSV[:, lower_bound]
74        spec_lower = c1 * gsv[0] + csm * gsv[3]
75        gsv = self.__GSV[:, upper_bound]
76        spec_upper = c1 * gsv[0] + csm * gsv[3]
77        spec = list(
78            map(lambda lr, ur, wl, lb: lr + (ur - lr) / 10 * (wl - lb * 10 - 400), spec_lower, spec_upper, wavelength,
79                lower_bound))
80        return spec
81
82
83if __name__ == "__main__":
84    # spec = gsv.get_soil_spectra_gsv3(np.arange(400, 2501, 10), 0.4, -0.01, 0.04, -0.13)
85    # plt.plot(np.arange(400, 2501, 10), spec)
86    # plt.ylim([0,1])
87    # plt.xlim([400, 2500])
88    # plt.show()
89    import matplotlib.pyplot as plt
90    gsv_model = GSVSoil()
91    for c1 in [0.3, 0.7]:
92        for c2 in [-0.1, 0]:
93            for c3 in [0, 0.05]:
94                for cSM in [-0.2, 0]:
95                    spectra = gsv_model.get_soil_spectra_gsv3(np.arange(400, 2501, 10), c1, c2, c3, cSM)
96                    plt.plot(np.arange(400, 2501, 10), spectra)
97    plt.show()