1. A water system sediment geochemical anomaly mapping method based on BME-GWR is characterized in that: the method comprises the following steps:

(1) extracting a terrain factor based on ASTGTM2DEM data, wherein the terrain factor comprises information of gradient, slope direction and terrain relief degree;

(2) constructing a probability type soft data model of the research area for the extracted terrain factors and the average rainfall information of the research area based on a GWR method;

(3) taking 1:20 million water system deposition geochemical data as hard data, and identifying geochemical abnormality of water system deposition in a research area on the basis of the established probability type soft data model and the hard data by a BME method;

(4) and comparing the geochemical abnormality of the identified water system sediments with a pockels interpolation result, and evaluating the interpolation precision and uncertainty.

2. The method for mapping geochemical anomaly of water system sediments based on BME-GWR as claimed in claim 1, wherein said extracting terrain factors including grade, slope and relief information based on ASTGTM2DEM data comprises the steps of:

carrying out mosaic fusion on the downloaded DEM data based on ArcGIS, cutting out DEM data with the same research area range, extracting factor information of gradient, slope direction and topographic relief degree, classifying according to the influence degree of the slope direction on water system sediments, and sequentially giving weights of 0-1 to 315-360 degrees, 0-45 degrees, 45-135 degrees, 225-315 degrees, 135-225 degrees from small to large, thereby carrying out normalization processing on the DEM data to obtain normalized influence factors.

3. The water system sediment geochemical anomaly mapping method based on BME-GWR as claimed in claim 1, wherein the method for constructing the probability soft data model of the research area based on GWR for the extracted topographic factor and the average rainfall information of the research area comprises the following steps:

firstly, normalizing the water system sediment according to the influence degree of rainfall on the water system sediment abnormity;

and secondly, acquiring a local average predicted value of the research area according to the extracted terrain factor and the average rainfall information of the research area based on a GWR method, and acquiring the mean value and the variance of the probability soft data according to the square of the difference between the predicted value and the actual measured value as the variance of the probability soft data.

4. The method for mapping geochemical anomaly of aqueous sediments based on BME-GWR as claimed in claim 1, wherein: and (3) taking 1:20 ten thousand water system deposition geochemical data as hard data, calculating the probability density distribution function of the unsampled points on the basis of the established probability type soft data model and the hard data by a BME method, and finally predicting the geochemical abnormal spatial distribution of the water system deposition in the research area by taking the mean value distribution as the estimated value of the unsampled points.

5. The method for mapping geochemical anomaly of aqueous sediments based on BME-GWR as claimed in claim 1, wherein: and comparing the identified geochemical anomaly of the water system sediments with the common Kriging result, calculating the mean value, the average absolute error and the root mean square error of the estimated values of the geochemical anomaly and the common Kriging result, calculating the correlation between the estimated values and the actually measured data, and evaluating the accuracy and the uncertainty of the estimated result.

6. An electronic device, characterized in that: comprising a memory, a processor and a computer program stored in the memory and running on the processor, the processor when executing the computer program implementing the steps of a method for geochemical anomaly mapping of water system sediments based on BME-GWR according to any one of claims 1 to 5.

7. A computer-readable storage medium characterized by: the computer readable storage medium stores a computer program which when executed by a processor implements the steps of a method for geochemical anomaly mapping of water based sediments for BME-GWR as defined in any one of claims 1 to 5.

Background

The geochemical anomaly identification method is one of the hotspots of geochemical exploration research, the integration and fusion of comprehensive information and data information related to mineralization are one of effective ways for solving the problems of geochemical information loss and incompleteness of a coverage area, and the method has important significance for developing geochemical anomaly information identification. The traditional anomaly identification method only relies on geochemical data for anomaly identification, and often cannot obtain satisfactory results. The abnormal distribution of the geochemical elements of the water system sediments is influenced by the surface geochemical landscape, so that the geochemical anomaly identification by combining the geochemical data of the water system sediments, the terrain influence factors and other information has important significance for the geochemical exploration. The Bayesian Maximum Entropy (BME) method is a space-time analysis and mapping method based on the space-time random field theory, and can comprehensively utilize geochemical data of the same research area at different periods and different precisions and geochemical landscape factors such as elevation and gradient influencing the distribution of geochemical elements, so as to effectively improve the prediction precision (Christakos, 1990; 1992). The geochemical abnormal distribution is influenced by various mutual restriction factors, and the terrain factor data, the average rainfall and the like are used as auxiliary data for geochemical abnormal identification, so that the problem of local data loss of the geochemical data can be solved, the prediction precision is improved, and the uncertainty of the geochemical abnormal identification is reduced. Therefore, the BME method is applied to geochemical anomaly information identification, and a new idea can be provided for identification and evaluation of geochemical anomalies.

Disclosure of Invention

The invention aims to provide a water system sediment geochemical anomaly mapping method based on BME-GWR, which improves the identification precision of water system sediment geochemical anomaly and reduces uncertainty.

In order to achieve the aim, the invention provides a water system sediment geochemical anomaly mapping method based on BME-GWR, which comprises the following steps:

(1) extracting a terrain factor based on ASTGTM2DEM data, wherein the terrain factor comprises information of gradient, slope direction and terrain relief degree;

(2) constructing a probability type soft data model of the research area for the extracted terrain factors and the average rainfall information of the research area based on a GWR method;

(3) taking 1:20 million water system deposition geochemical data as hard data, and identifying geochemical abnormality of water system deposition in a research area on the basis of the established probability type soft data model and the hard data by a BME method;

(4) and comparing the geochemical abnormality of the identified water system sediments with a pockels interpolation result, and evaluating the interpolation precision and uncertainty.

Preferably, the extracting of the terrain factors including the information of the gradient, the slope direction and the terrain relief degree based on the ASTGTM2DEM data comprises the following steps:

carrying out mosaic fusion on the downloaded DEM data based on ArcGIS, cutting out DEM data with the same research area range, extracting factor information of gradient, slope direction and topographic relief degree, classifying according to the influence degree of the slope direction on water system sediments, and sequentially giving weights of 0-1 to 315-360 degrees, 0-45 degrees, 45-135 degrees, 225-315 degrees, 135-225 degrees from small to large, thereby carrying out normalization processing on the DEM data to obtain normalized influence factors.

Preferably, the method for constructing the probability soft data model of the research area based on the GWR method for the extracted terrain factors and the average rainfall information of the research area comprises the following steps:

firstly, normalizing the water system sediment according to the influence degree of rainfall on the water system sediment abnormity;

and secondly, acquiring a local average predicted value of the research area according to the extracted terrain factor and the average rainfall information of the research area based on a GWR method, and acquiring the mean value and the variance of the probability soft data according to the square of the difference between the predicted value and the actual measured value as the variance of the probability soft data.

Preferably, 1:20 million water system deposition geochemical data are taken as hard data, probability density distribution functions of non-sampling points are calculated on the established probability type soft data model and the hard data based on a BME method, mean value distribution is taken as an estimated value of the non-sampling points, and finally geochemical abnormal spatial distribution of water system deposition in the research area is predicted.

Preferably, the geochemical abnormality of the identified water system sediments is compared with the common kriging result, the mean value, the average absolute error and the root mean square error of the estimated values of the geochemical abnormality and the common kriging result are calculated, the correlation between the estimated values and the actually measured data is calculated, and the uncertainty evaluation of the estimated result is carried out.

An electronic device comprising a memory, a processor and a computer program stored in the memory and running on the processor, the processor implementing the steps of the above-described method for mapping geochemical anomalies of water system sediments based on BME-GWR when executing the computer program.

A computer readable storage medium storing a computer program which when executed by a processor implements the steps of a method for mapping geochemical anomalies of water based sediments for BME-GWR as described above.

Therefore, the water system sediment geochemical anomaly mapping method based on the BME-GWR with the structure improves the identification precision of the water system sediment geochemical anomaly and reduces the uncertainty.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

FIG. 1 is a flow chart of a method for mapping geochemical anomalies of water based deposits based on BME-GWR;

FIG. 2 is a diagram of a slope, a sloping direction, a relief degree and an average rainfall distribution extracted based on ASTGTM2DEM remote sensing data;

FIG. 3 is a normalized distribution graph of extracted slope, direction of slope, relief and average rainfall;

figure 4 is a GWR prediction profile based on normalized slope, direction of slope, relief and average rainfall;

FIG. 5 is a graph of spatial distribution of Mo element content for a study area based on BME and common kriging (OK);

FIG. 6 is a first plot of correlation coefficients between BME and general kriging (OK) predictions and measurement data;

FIG. 7 is a second plot of correlation coefficients between BME and general kriging (OK) predictions and measurement data.

Detailed Description

The technical solution of the present invention is further illustrated by the accompanying drawings and examples.

The invention provides a water system sediment geochemical anomaly mapping method based on BME-GWR, which comprises the following steps:

(1) extracting terrain factors based on ASTGTM2DEM data, wherein the terrain factors comprise information of gradient, slope direction and terrain relief degree, and the method comprises the following steps:

carrying out mosaic fusion on the downloaded DEM data based on ArcGIS, cutting out DEM data with the same research area range, extracting factor information of gradient, slope direction and topographic relief degree, classifying according to the influence degree of the slope direction on water system sediments, and sequentially giving weights of 0-1 to 315-360 degrees, 0-45 degrees, 45-135 degrees, 225-315 degrees, 135-225 degrees from small to large, thereby carrying out normalization processing on the DEM data to obtain normalized influence factors.

(2) The method for constructing the probability type soft data model of the research area on the basis of the GWR method for the extracted terrain factors and the average rainfall information of the research area comprises the following steps:

firstly, normalizing the water system sediment according to the influence degree of rainfall on the water system sediment abnormity;

and secondly, acquiring a local average predicted value of the research area according to the extracted terrain factor and the average rainfall information of the research area based on a GWR method, and acquiring the mean value and the variance of the probability soft data according to the square of the difference between the predicted value and the actual measured value as the variance of the probability soft data.

(3) Taking 1: 20-kilo-water system deposition geochemical data as hard data, calculating a probability density distribution function of an unsampled point for the established soft data model and the hard data based on a BME method, and finally predicting the geochemical abnormal spatial distribution of the water system deposits in the research area by taking mean distribution as an estimated value of the unsampled point;

(4) and comparing the identified geochemical anomaly of the water system sediments with an Ordinary Kriging (OK) result, calculating the mean value, the average absolute error and the root mean square error of the estimated values of the geochemical anomaly and the Ordinary Kriging (OK) result, calculating the correlation between the estimated values and the actually measured data, and evaluating the accuracy and the uncertainty of the estimated result.

An electronic device comprising a memory, a processor and a computer program stored in the memory and running on the processor, the processor implementing the steps of the above-described method for mapping geochemical anomalies of water system sediments based on BME-GWR when executing the computer program.

A computer readable storage medium storing a computer program which when executed by a processor implements the steps of a method for mapping geochemical anomalies of water based sediments for BME-GWR as described above.

As shown in fig. 1, a method for mapping geochemical anomaly of water system sediments based on BME-GWR comprises the following steps:

s110: a priori stage: a priori PDF calculation based on maximum entropy.

Based on the principle of maximum entropy, namely, in the case of limited provided data or incomplete probability space, when estimating the probability distribution of random variables, selecting one probability distribution with the maximum entropy as the prior result of estimation. And in the prior stage, qualitative knowledge is converted into quantitative mathematical constraint, prior distribution with the maximum information content is found out, and the most abundant prior information is ensured to be merged into the estimation process. Assume a random variable X_map＝(x₁,x₂,...,x_m,x_k) With corresponding spatial coordinates of [ p ]₁,p₂,...,p_m,p_k]，x_kRepresenting the value, f, at a certain point pk to be estimated_G(X_map) Represents X_mapThe PDF of (a). The information entropy calculation formula is as follows:

H[X_map，f_G(X_map)]＝-∫ln[f_G(X_map)]f_G(X_map)dX_map (1)

where formula (1) takes a maximum value under the constraint, the general formula of the constraint can be represented as:

E[g_α]＝∫g_α(X_map)f_G(X_map)dX_map (2)

g_α(X_map) With respect to X_mapIs always a given function, the number of the constraint condition α ═ 2 [, ]1,2,…,Nc]And X_mapG commonly used, depending on the total number (m +1)_α(X_map) In the form of normalization constraints, mathematical expectation constraints, variance constraints, covariance constraints, and statistical constraints with variogram models and multiple points.

S120: and in the posterior stage, the posterior PDF calculation based on Bayes is carried out.

Constructing a soft data model based on geographic weighted regression: soft data generally has different degrees of correlation with estimated target variables, and contains abundant information. The discrete variables selected in the embodiment are mainly slope data, and the weight is 315-360 degrees, 0-45 degrees, 45-135 degrees, 225-315 degrees, 135-225 degrees and sequentially given weight values within 0-1 according to the influence degree on the formation of the secondary corona of the water system sediments; and the average rainfall data and the like in the continuous variable, the gradient and the topographic relief are obtained through ASTGTM2DEM remote sensing data. The invention constructs probability soft data based on a geographical weighted regression method,

wherein u is a point location to be predicted, q is a matrix of k multiplied by 1, k is the number of auxiliary variables,expressing the linear regression coefficient by the formula

Where W (u) is an n × n weight matrix at u as a function of the distance d between the points

w(uu′)＝exp(-d²/2b²) The weight n is the number of modeling points in the neighborhood of the distance b, and z (n), which is an attribute value in the neighborhood, is calculated as an n × 1 vector. Sigma_GWR(u) is the standard deviation, and the calculation formula is as follows:

is the mean square error.

And calculating the posterior PDF of the unmeasured points.

The posterior PDF of the variable X at the predicted position pk is:

wherein x is_hard＝[x₁,x₂,...,x_h]，x_soft＝[x_h+1,x_h+2,...,x_m]And h, m-h are the number of hard data and soft data in a certain range around the point to be predicted respectively.

S130: and identifying and evaluating geochemical abnormal information.

The obtained posterior PDF is generally non-Gaussian distribution and can describe the complete distribution characteristics of the position attribute of an unknown point. According to different drawing purposes, different values can be extracted and given to each point as a pixel value in the geochemical drawing, such as BME mode estimation, which represents a predicted value most likely to appear; BME mean estimate, representing the predicted value with the minimum mean square estimation error; the BME median estimate, representing the predicted value with the smallest mean absolute error. According to the purpose of the invention, the BME mean value estimation is selected as a geochemical estimation value to carry out geochemical anomaly identification.

Variance measure prediction accuracy of a posterior probability:

the variance corresponds to an estimated variance error, depends on the selected soft data and hard data set, can measure the prediction accuracy of a distribution function when posterior probability distribution is not complex, and measures the prediction accuracy by using a confidence domain when posterior PDF distribution is complex.

Examples

In the embodiment, a coverage area of Nemonton Guining is taken as a research area, 1:20 million of geochemical data of the research area is taken as hard data, gradient, slope direction and topographic relief data of the research area are extracted and collected average rainfall data of the research area are preprocessed on the basis of ASTGTM2DEM respectively, and slope direction weights are sequentially given to weight values within 0-1 from small to large of 315-360 degrees, 0-45 degrees, 45-135 degrees, 225-315 degrees and 135-225 degrees according to the influence degree on the formation of the sub-halation of water system sediments. And carrying out normalization processing on the gradient and the average rainfall data to obtain normalized spatial distribution of topographic and climatic influence factors of the water system sediments in the research area. And constructing probability type soft data of the variables based on a geographical weighted regression method. And (3) taking 1: 20-kilo-water system deposition geochemical data as hard data, calculating a probability density distribution function of an unsampled point on the basis of the established soft data model and the hard data by a BME method, and finally predicting the geochemical abnormal spatial distribution of the water system deposits in the research area by taking mean distribution as an estimated value of the unsampled point.

The identified water system deposit geochemical anomaly is compared with the common kriging (OK) results, and the spatial distribution trends of the two identified anomalies are similar, but the BME suppresses some terrain or smoothing-induced false anomalies, revealing some local anomalies and weak anomaly distributions under the cover. And calculating the mean value, the average absolute error and the root mean square error of the two estimated values, wherein the average absolute error and the root mean square error of the prediction result based on the BME are smaller, and the scatter diagram shows that the correlation between the BME estimated value and actually measured data is better, which shows that the uncertainty and the precision of the prediction result of the water system sediment abnormality integrated with the topographic factor and the climatic factor recognition are lower.

With reference to fig. 1, a calculation flow chart is obtained.

With reference to fig. 2, the average rainfall and the spatial distribution of the slope, the direction of the slope and the relief degree extracted based on the ASTGTM2DEM are obtained through the step (1).

With reference to fig. 3, the spatial distribution is normalized for the average rainfall extracted in step (1) and the slope, direction and relief extracted based on ASTGTM2 DEM.

With reference to fig. 4, the soft data mean distribution obtained through step (2) GWR.

With reference to fig. 5, abnormal distribution of water-based sediments in the study area based on BME and OK is obtained through step (3).

With reference to fig. 6 and 7, a scatter plot of the predicted values and observed values of BME and OK is obtained through step (4).

And (5) combining the table 1, and obtaining a predicted value cross validation parameter table of the BME and the OK through the step (4).

TABLE 1

The terminal device of this embodiment includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. The processor, when executing the computer program, implements the steps in the above-described method embodiments, such as steps S110 to S130 shown in fig. 1.

All or part of the flow of the method of the embodiments may be implemented by a computer program, which may be stored in a computer readable storage medium and executed by a processor, to instruct related hardware to implement the steps of the embodiments of the methods. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, usb disk, removable hard disk, magnetic disk, optical disk, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, software distribution medium, and the like.

Therefore, the water system sediment geochemical anomaly mapping method based on the BME-GWR with the structure improves the identification precision of the water system sediment geochemical anomaly and reduces the uncertainty.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the invention without departing from the spirit and scope of the invention.