CN103926203A - Spectral angle mapping method aiming at ground object spectrum uncertainty - Google Patents

Abstract

The present invention proposes a spectral angle mapping method for the spectral uncertainty of surface objects, including: obtaining a test spectrum and a reference spectrum; using the test spectrum and the reference spectrum to calculate the spectral difference, and constructing and calculating the spectral difference according to the spectral difference. The vector of the test spectrum has the same dimension and the spectral difference vector of the equal size of each component; use the spectral difference vector to calculate the spectral angle between the test spectrum and the reference spectrum under the uncertainty of the feature spectrum; according to the The above spectral angles are used for spectral angle mapping. The method proposed by the present invention is used to obtain the spectral angle between the test spectrum and the reference spectrum through the spectral difference amount under the uncertainty of the ground object spectrum, and perform spectral angle mapping according to the obtained spectral angle, so as to overcome the uncertainty caused by the ground object spectrum The impact of this method improves the accuracy of surface object recognition and has better applicability to surface object spectral uncertainty.

Description

A Spectral Angle Mapping Method Aiming at Spectral Uncertainty of Ground Objects

technical field

The invention relates to the technical field of remote sensing, in particular to a spectral angle mapping method aimed at the spectral uncertainty of ground objects, which is used for hyperspectral remote sensing mineral mapping and target identification.

Background technique

Hyperspectral remote sensing data provide a large amount of spectral information of ground objects, which is conducive to fine classification and quantitative remote sensing of ground objects. Spectral angle mapping algorithm (Spectral angle mapping, SAM) is an algorithm based on the overall similarity of spectral curves, which is widely used in the classification of hyperspectral remote sensing information.

The spectral angle mapping algorithm calculates the similarity of the entire spectral curve, which is a global description index, and it is poor in distinguishing features with similar spectral curves. At present, the spectral angle mapping algorithm is mainly improved by setting the weight of the local interval, selecting the band combination and introducing the kernel function. Specific improvement methods can be found in Document 1: He Zhonghai, He Binbin. Hyperspectral Mineral Mapping Method Based on Weighted Spectral Angle Mapping [J]. Spectroscopy and Spectral Analysis, 2011, 31(8): 2200-2204 and Document 2: Lu Yinliang , Li Shaokun, Wang Keru, et al. Research on Wheat Yield Monitoring Based on Improved Spectral Angle Algorithm[J]. Xinjiang Agricultural Sciences, 2011, 48(001): 1-5 and Document 3: Gu Y, Wang C, Wang S, et al .Kernel-based regularized-anglespectral matching for target detection in hyperspectral imagery[J].PatternRecognition Letters,2011,32(2):114-119. However, the uncertainty of the spectrum of the ground object often causes a certain degree of difference between the spectra of the same type of ground object, which affects the recognition accuracy of the ground object, and will also have a certain impact on the recognition effect of the ground object by the spectral angle mapping algorithm.

Contents of the invention

(1) Technical problems to be solved

The purpose of the present invention is to provide a spectral angle mapping method for the spectral uncertainty of ground objects, so as to solve the problem that the existing spectral angle mapping methods do not consider the spectral uncertainty of ground objects.

(2) Technical solution

In order to achieve the above object, the present invention proposes a spectral angle mapping method aimed at the spectral uncertainty of ground objects, including:

Obtain test spectrum and reference spectrum;

Using the test spectrum and the reference spectrum to calculate the amount of spectral difference, and constructing a spectral difference vector having the same dimension as the vector of the test spectrum and equal in size to each component according to the amount of spectral difference;

Using the spectral difference vector to calculate the spectral angle between the test spectrum and the reference spectrum in the case of ground object spectral uncertainty;

Spectral angle mapping is performed according to the spectral angles.

Preferably, said obtaining test spectrum and reference spectrum specifically includes:

Using hyperspectral imagery, measured spectral data or spectral library to obtain the test spectrum;

The reference spectrum is obtained by using a hyperspectral image, measured spectral data or a spectral library.

Preferably, the calculation of the spectral difference using the test spectrum and the reference spectrum specifically includes:

Obtain the spectrum vectors of the test spectrum and the reference spectrum;

Calculate the spectral difference n according to the spectral vector of the obtained test spectrum and reference spectrum, the formula is as follows:

$\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; nb</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span>}$

in, $\stackrel{\&Right\; Arrow;}{t}=(t_1,t_2,...,t_{\mathrm{nb}})$ represents the test spectrum vector, $\stackrel{\&Right\; Arrow;}{r}=(r_1,r_2,...,r_{\mathrm{nb}})$ Indicates and refers to the spectral vector, nb represents the dimension of the spectral vector, and i is any integer between 1 and nb.

Preferably, the calculation of the spectral angle between the test spectrum and the reference spectrum under the condition of surface object spectral uncertainty by using the spectral difference vector specifically includes:

Calculate the cosine value of the spectral angle between the test spectrum and the reference spectrum in the case of ground object spectral uncertainty according to the spectral difference vector, the formula is as follows:

$\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; \text{'}</span><span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; +</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}}{<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; +</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>}$

in, $\stackrel{\&Right\; Arrow;}{t}=(t_1,t_2,...,t_{\mathrm{nb}})$ represents the test spectrum vector, $\stackrel{\&Right\; Arrow;}{r}=(r_1,r_2,...,r_{\mathrm{nb}})$ represent and reference spectral vectors, Represent spectral difference vector, n is the amount of spectral difference, and α' is the spectral angle between the test spectrum vector and the reference spectrum vector under the situation of spectral difference amount;

Based on the principle of maximizing the cosine of the spectral angle between the spectra of the same kind of ground objects, the spectral angle between the test spectrum and the reference spectrum is calculated in the case of the uncertainty of the spectrum of the ground objects according to the cosine value of the spectral angle.

Preferably, the test spectrum is a spectrum obtained after removing four strong water vapor absorption bands within the solar reflection spectrum range of 350-2500 nm.

Preferably, the reference spectrum is the spectrum obtained after removing the four water vapor strong absorption bands within the solar reflection spectrum range of 350-2500 nm.

Preferably, the four water vapor strong absorption bands include: 900-990nm, 1100-1190nm, 1300-1520nm and 1750-2080nm.

(3) Beneficial effects

A spectral angle mapping method aimed at the spectral uncertainty of ground objects proposed by the present invention can effectively characterize the difference of the spectrum of the same kind of ground objects by using the amount of spectral difference, overcome the influence of the spectral uncertainty of ground objects and improve the accuracy of ground object recognition Accuracy, better applicability to ground object spectral uncertainty.

Description of drawings

Fig. 1 is a kind of flow chart of the present invention for the method for spectral angle drawing of surface feature spectral uncertainty;

Fig. 2 is the kaolinite reference spectrum selected from the USGS standard spectral library in the embodiment of the present invention;

Fig. 3 is the kaolinite test spectrum selected from the USGS standard spectral library in the embodiment of the present invention.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

Fig. 1 is the flow chart of a kind of spectral angle drawing method of the present invention aiming at the spectral uncertainty of surface object, as shown in the figure, the embodiment of the present invention comprises the following steps:

S101. Obtain a test spectrum and a reference spectrum; mainly including acquiring the test spectrum and the reference spectrum by using a hyperspectral image, measured spectral data or a spectral library.

In the embodiment of the present invention, the reference spectrum of kaolinite is selected from the USGS standard spectral library. As shown in Figure 2, four bands with strong absorption of water vapor have been removed: 900-990nm, 1100-1190nm, 1300-1520nm, 1750-2080nm; Select the test spectrum of kaolinite from the USGS standard spectral library, as shown in Figure 3, four bands with strong absorption of water vapor have been removed: 900-990nm, 1100-1190nm, 1300-1520nm, 1750-2080nm.

S102. Using the test spectrum and the reference spectrum to calculate the spectral difference, and constructing a spectral difference vector having the same dimension as the vector of the test spectrum and having the same size as the vector of the test spectrum according to the spectral difference, specifically including:

In the embodiment of the present invention, by obtaining the spectrum vectors of the test spectrum and the reference spectrum, and calculating the spectrum difference n according to the spectrum vectors obtained from the test spectrum and the reference spectrum, the formula is as follows:

$\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; nb</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span>}$

in, $\stackrel{\&Right\; Arrow;}{t}=(t_1,t_2,...,t_{\mathrm{nb}})$ represents the test spectrum vector, $\stackrel{\&Right\; Arrow;}{r}=(r_1,r_2,...,r_{\mathrm{nb}})$ Represents and refers to the spectral vector, nb represents the dimension of the spectral vector, and i is any integer between 1 and nb. The calculated spectral difference n value is 0.0899.

S103. Using the spectral difference vector to calculate the spectral angle between the test spectrum and the reference spectrum in the case of ground object spectral uncertainty, specifically including:

In the embodiment of the present invention, the spectral difference n (n=0.0899) obtained from step S103 is obtained, and the cosine of the spectral angle between the test spectrum and the reference spectrum is calculated according to the spectral difference vector in the case of ground object spectral uncertainty value, the formula is as follows:

$\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; \text{'}</span><span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; +</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}}{<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; +</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>}$

in, $\stackrel{\&Right\; Arrow;}{t}=(t_1,t_2,...,t_{\mathrm{nb}})$ represents the test spectrum vector, $\stackrel{\&Right\; Arrow;}{r}=(r_1,r_2,...,r_{\mathrm{nb}})$ represent and reference spectral vectors, Represent spectral difference vector, n is the amount of spectral difference, and α' is the spectral angle between the test spectrum vector and the reference spectrum vector under the situation of spectral difference amount;

Based on the principle of maximizing the cosine of the spectral angle between the spectra of the same kind of ground objects, the spectral angle between the test spectrum and the reference spectrum is calculated in the case of the uncertainty of the spectrum of the ground objects according to the cosine value of the spectral angle.

The spectral angle α' between the test spectrum and the reference spectrum obtained in the embodiment of the present invention under the condition of ground object spectral uncertainty is 0.0069 radians. The spectral angle calculated without considering the spectral difference is 0.0177 radians, and it can be seen that the calculation result of the improved spectral angle has been greatly improved.

S104. Perform spectral angle mapping according to the spectral angle, and perform spectral angle mapping according to the improved spectral angle, which effectively improves the accuracy of object recognition.

Adopt a kind of spectral angle charting method aiming at the spectral uncertainty of surface objects proposed by the present invention, obtain the spectral angle between the test spectrum and the reference spectrum under the condition of spectral difference by spectral difference, according to the obtained spectral angle Carry out spectral angle mapping, overcome the influence caused by the spectral uncertainty of ground objects and improve the accuracy of ground object recognition, and have better applicability to the spectral uncertainty of ground objects.

The above embodiments are only used to illustrate the present invention, but not to limit the present invention. Those of ordinary skill in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all Equivalent technical solutions also belong to the category of the present invention, and the scope of patent protection of the present invention should be defined by the claims.

Claims (7)

1. A spectral angle mapping method for ground object spectral uncertainty, characterized in that, comprising: Obtain test spectrum and reference spectrum; Using the test spectrum and the reference spectrum to calculate the amount of spectral difference, and constructing a spectral difference vector having the same dimension as the vector of the test spectrum and equal in size to each component according to the amount of spectral difference; Using the spectral difference vector to calculate the spectral angle between the test spectrum and the reference spectrum in the case of ground object spectral uncertainty; Spectral angle mapping is performed according to the spectral angles. 2. The method according to claim 1, wherein said obtaining test spectrum and reference spectrum specifically comprises: Using hyperspectral imagery, measured spectral data or spectral library to obtain the test spectrum; The reference spectrum is obtained by using a hyperspectral image, measured spectral data or a spectral library. 3. The method according to claim 1, wherein the calculation of spectral difference using test spectrum and reference spectrum specifically comprises: Obtain the spectrum vectors of the test spectrum and the reference spectrum; Calculate the spectral difference n according to the spectral vector of the obtained test spectrum and reference spectrum, the formula is as follows: $\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; nb</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span>}$ in, $\stackrel{\&Right\; Arrow;}{t}=(t_1,t_2,...,t_{\mathrm{nb}})$ represents the test spectrum vector, $\stackrel{\&Right\; Arrow;}{r}=(r_1,r_2,...,r_{\mathrm{nb}})$ Represents and refers to the spectral vector, nb represents the dimension of the spectral vector, and i is any integer between 1 and nb. 4. the method as claimed in claim 1 or 3, is characterized in that, described utilizing spectral difference vector to calculate the spectral angle between described test spectrum and reference spectrum under the situation of feature spectral uncertainty specifically comprises: Calculate the cosine value of the spectral angle between the test spectrum and the reference spectrum in the case of ground object spectral uncertainty according to the spectral difference vector, the formula is as follows: $\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; \text{'}</span><span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; +</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}}{<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; +</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>}$ in, $\stackrel{\&Right\; Arrow;}{t}=(t_1,t_2,...,t_{\mathrm{nb}})$ represents the test spectrum vector, $\stackrel{\&Right\; Arrow;}{r}=(r_1,r_2,...,r_{\mathrm{nb}})$ represent and reference spectral vectors, Represent spectral difference vector, n is the amount of spectral difference, and α' is the spectral angle between the test spectrum vector and the reference spectrum vector under the situation of spectral difference amount; Based on the principle of maximizing the cosine of the spectral angle between the spectra of the same kind of ground objects, the spectral angle between the test spectrum and the reference spectrum is calculated in the case of the uncertainty of the spectrum of the ground objects according to the cosine value of the spectral angle. 5 . The method according to claim 1 , wherein the test spectrum is a spectrum obtained after removing four water vapor strong absorption bands within the solar reflection spectrum range of 350-2500 nm. 6 . 6. The method according to claim 1 or 5, wherein the reference spectrum is the spectrum obtained after removing the four water vapor strong absorption bands within the solar reflection spectrum range of 350-2500 nm. 7. The method according to claim 6, wherein the four water vapor strong absorption bands include: 900-990 nm, 1100-1190 nm, 1300-1520 nm and 1750-2080 nm.