Land Change Degree Assessment Method, System and Storage Medium Based on Gradient Division and Two-Dimensional Analysis

Abstract

This application relates to the technical field of land use change evaluation, and particularly to a land change degree evaluation method, system and storage medium based on gradient division and two-dimensional analysis. The land to be evaluated is divided into target sub-regions with multiple different target gradients by using the topographic position index; wherein, the topographic position index is calculated from the elevation value and slope value of the land; the target sub-regions are analyzed from two evaluation dimensions, namely the topographic gradient effect dimension and the land gradient utilization characteristic dimension, and based on the evaluation results of the topographic gradient effect and the evaluation results of the land gradient utilization characteristic dimension of the obtained multiple target sub-regions, the evaluation result of the land change degree of the land to be evaluated is determined. It aims to solve the problem of how to evaluate land use change in areas with obvious vertical zonality and altitude gradient.

Description

Technical Field

[0001] The present application relates to the technical field of land use change evaluation, and particularly relates to a land change degree evaluation method, system and storage medium based on gradient division and two-dimensional analysis. Background Art

[0002] Land use is the way and condition of human use of the natural attributes of land, and it is also the most direct manifestation of the interaction between humans and nature. As an embodiment of the surface height and shape, terrain drives the distribution of resources and human activities through the migration of surface materials and energy conversion, and determines the formation of the national land space pattern. Clarifying the role of terrain in the development and utilization of national land space is the basis and prerequisite for analyzing the carbon emission effect of land gradient utilization and its regulation.

[0003] In related technical solutions, the Chinese patent with the application number CN202111363830.7 discloses a method for evaluating land use change in mountainous areas based on terrain gradient, which mainly includes four steps: quantifying terrain gradient, constructing an evaluation system, collecting and analyzing original data, and generating evaluation results. By systematically exploring the terrain differentiation characteristics and change laws of land use in mountainous areas from the perspectives of altitude, slope, terrain position, etc., and constructing a land use vertical gradient index with administrative units, the local characteristics of land use vertical differentiation are deeply described.

[0004] However, in the above technical solution, the calculation of the terrain position index in land use change evaluation is carried out with the traditional whole research area as the object, and only a single land use dynamic degree is used to evaluate land use change. When this evaluation method is used in areas with obvious vertical zonality and altitude gradient, such as the central and eastern parts of Yunnan, where various land types such as cultivated land, forest land, grassland, water area and urban land are significantly affected by altitude, there is a problem of inaccurate land use change evaluation.

[0005] In view of this, a land change degree evaluation method that can meet the need for accurate land use change evaluation of complex land is required. Summary of the Invention

[0006] The main purpose of the present application is to provide a land change degree evaluation method based on gradient division and two-dimensional analysis, aiming to solve the problem of how to evaluate land use change in areas with obvious vertical zonality and altitude gradient.

[0007] To achieve the above object, a land change degree evaluation method based on gradient division and two-dimensional analysis provided by the present application includes:

[0008] Dividing the land to be evaluated into target sub-regions with multiple different target gradients by using the terrain position index; wherein, the terrain position index is calculated from the elevation value and slope value of the land.

[0009] Analyze the target sub-region from two evaluation dimensions: the dimension of topographic gradient effect and the dimension of land gradient utilization characteristics, and determine the evaluation result of the land change degree of the land to be evaluated based on the evaluation results of the topographic gradient effect and the evaluation results of the land gradient utilization characteristics dimension of the obtained multiple target sub-regions.

[0010] Optionally, the step of dividing the land to be evaluated into multiple target sub-regions with different target gradients by using the topographic position index specifically includes:

[0011] Divide the land to be evaluated into multiple sub-regions with the target radius range as a unit;

[0012] Calculate the topographic position index corresponding to each of the sub-regions;

[0013] Determine the target gradient where each of the sub-regions is located according to the numerical interval where the topographic position index corresponding to each of the sub-regions is located;

[0014] Determine the sub-regions in the same target gradient as the target sub-region composed of one or more of the sub-regions.

[0015] Optionally, the elevation value and the slope value are obtained from the digital elevation model data of the land to be evaluated, and the calculation steps of the topographic position index include:

[0016] Select any pixel in the land to be evaluated as the target pixel with the pixel as a unit, and take the average of the elevation values and slope values of all pixels within the target radius range centered on the target pixel to obtain the average elevation value and average slope value of the target pixel;

[0017] Based on the elevation value, slope value of the target pixel, as well as the average elevation value and the average slope value, calculate the topographic position index within the target radius range:

[0018]

[0019] In the formula, is the local window topographic position index of the pixel in the i-th row and j-th column under the local window of the target radius range R; is the local window centered on the target pixel at the (i, j) position, and are the elevation value and slope value of the target pixel respectively, is the average elevation value, is the average slope value.

[0020] Optionally, the land gradient utilization feature dimension includes at least one of three dimensions: the area change of land use types, the change trend of land gradient utilization degree, and the change of land gradient utilization structure. The evaluation result of the land gradient utilization feature dimension includes:

[0021] Obtain the land type areas of the target sub-regions with different target gradients, construct the land use transfer matrix of the land to be evaluated based on the land type areas of each target sub-region, and analyze the area change of the land use types in the historical period of the land to be evaluated based on the land use transfer matrix;

[0022] Calculate the comprehensive land utilization degree indexes of the target sub-regions in two different historical periods respectively, obtain the first comprehensive land utilization degree index and the second comprehensive land utilization degree index, calculate the change rate of land utilization degree of the target sub-region according to the first comprehensive land utilization degree index and the second comprehensive land utilization degree index, and analyze the change trend of land gradient utilization degree in the land to be evaluated based on the change rates of land utilization degree of each target sub-region;

[0023] Calculate the information entropy of the target sub-region, calculate the equilibrium degree index of the target sub-region according to the information entropy, and analyze the change of the land gradient utilization structure of the land to be evaluated based on the information entropy and / or the equilibrium degree index of each target sub-region. The change of the land gradient utilization structure includes the stability of the land use structure and the homogeneity of land gradient utilization.

[0024] Optionally, the calculation expression of the land use transfer matrix is:

[0025]

[0026] In the formula, is the land use transfer matrix, that is, The area of the land type converted to The area of the land type; Represents the land type areas under different gradient levels; are the land type codes before and after the transfer.

[0027] Optionally, the calculation expression of the comprehensive land utilization degree index is:

[0028]

[0029] In the formula, Represents the change rate of land utilization degree, is the grading index of land gradient utilization degree, is the proportion of the grading area of land gradient utilization degree;

[0030] The calculation expression of the land use degree change rate is as follows:

[0031]

[0032] In the formula, R is the land use degree change rate, is the first land comprehensive utilization degree index, is the second land comprehensive utilization degree index, and a and b represent two different historical periods.

[0033] Optionally, the calculation expression of the information entropy is:

[0034]

[0035] The calculation expression of the equilibrium degree index is:

[0036]

[0037] In the formula, represents the information entropy; represents the equilibrium degree index, is the proportion of the area of each land type under the same target gradient to the total land area of the target gradient; n is the number of land use types.

[0038] Optionally, the terrain gradient effect dimension includes at least one of elevation value, slope value, terrain undulation degree, and distribution index.

[0039] In addition, to achieve the above object, the present application also provides a computer system, which includes: a memory, a processor, and a land gradient utilization change evaluation program stored on the memory and executable on the processor. When the land gradient utilization change evaluation program is executed by the processor, the steps of the land change degree evaluation method based on gradient division and two-dimensional analysis as described in any one of the above are implemented.

[0040] In addition, to achieve the above object, the present application also provides a computer-readable storage medium, on which a land gradient utilization change evaluation program is stored. When the land gradient utilization change evaluation program is executed by a processor, the steps of the land change degree evaluation method based on gradient division and two-dimensional analysis as described in any one of the above are implemented.

[0041] The present application has at least the following beneficial effects:

[0042] 1. The topographic position index calculated using elevation values and slope values divides the land to be evaluated into multiple target sub-regions with different target gradients. After evaluating the topographic gradient effect and land gradient utilization characteristics of each target sub-region in two dimensions, the evaluation result of the land change degree of the land to be evaluated is comprehensively obtained, realizing the accurate evaluation of complex land areas, and providing an analysis basis for subsequent research and regulation of the carbon emission effect of complex land areas.

[0043] 2. By introducing gradient levels to divide the land to be evaluated to analyze the land use characteristics in the vertical direction, and analyzing the land use distribution and changes under different gradient levels, it not only considers the overall impact of terrain on land use, but also deeply analyzes the characteristics of the spatial distribution and spatial changes of different land use types under the conditions of land vertical differentiation and gradient stratification, realizing the accurate evaluation of land areas with obvious vertical zonality and altitude gradient. Brief Description of the Drawings

[0044] Figure 1 It is a schematic flowchart of the first embodiment of the land change degree evaluation method based on gradient division and two-dimensional analysis of the present application;

[0045] Figure 2 It is a schematic diagram of the transfer of land gradient utilization types in the central Yunnan urban agglomeration from 2000 to 2020 involved in the embodiment of the present application;

[0046] Figure 3 It is a spatial distribution map of the change in land gradient utilization degree in the central Yunnan urban agglomeration from 2000 to 2020 involved in the embodiment of the present application;

[0047] Figure 4 It is a schematic architecture diagram of the hardware operating environment of the computer system involved in the embodiment of the present application.

[0048] The realization, functional features and advantages of the purpose of the present application will be further described with reference to the embodiments and the accompanying drawings. Detailed Embodiment

[0049] To better understand the above technical solutions, the exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art.

[0050] First Embodiment

[0051] Refer to Figure 1, in this embodiment, the land change degree evaluation method based on gradient division and two-dimensional analysis includes the following steps:

[0052] S10, using the topographic position index to divide the land to be evaluated into multiple target sub-regions with different target gradients; wherein, the topographic position index is calculated from the elevation value and slope value of the land;

[0053] In this embodiment, traditional evaluation methods often take the entire land to be evaluated as a reference, but for complex land areas, they cannot reflect the topographic differences between local regions. Therefore, this embodiment proposes to use the topographic position index to divide the entire land to be evaluated.

[0054] The topographic position index (Topographic Position Index, TPI) is an index used to describe topographic features. The traditional topographic position index is mainly obtained by comparing the elevation value of a grid point with the average elevation value of its surrounding area. However, the topographic position index proposed in this embodiment is calculated using the elevation value and slope value.

[0055] Optionally, the calculation steps of the topographic position index in this embodiment are as follows:

[0056] Step S11, select any pixel in the land to be evaluated as the target pixel in units of pixels. Taking the target pixel as the center, take the elevation values and slope values of all pixels within the target radius range and average them to obtain the average elevation value and average slope value of the target pixel;

[0057] Step S12, based on the elevation value, slope value of the target pixel, as well as the average elevation value and the average slope value, calculate the topographic position index within the target radius range:

[0058]

[0059] In the formula, is the local window topographic position index of the pixel in the i-th row and j-th column under the local window of the target radius range R; is the local window centered on the target pixel at the (i, j) position, and are the elevation value and slope value of the target pixel respectively, is the average elevation value, is the average slope value.

[0060] Optionally, the elevation value and slope value in the embodiment can both be obtained through Digital Elevation Model (DEM) data.

[0061] In a specific embodiment, the initial DEM data downloaded from the Earth Science Data website of the National Aeronautics and Space Administration (NASA) can be selected. The spatial resolution is 12.5m × 12.5m (i.e., the size of one pixel is 12.5m). Compared with the data of two types of products, SRTM and ASTER, its resolution and three-dimensional details are the best, which can meet the research requirements for higher-precision data analysis and mapping, show the three-dimensional characteristics of the central Yunnan urban agglomeration as much as possible, and improve the calculation accuracy. After preprocessing the downloaded initial DEM product data, such as projection, mosaicking, extraction, resampling, surface analysis, etc., the digital elevation model data containing elevation values and slope values required in this embodiment can be obtained.

[0062] Optionally, regarding how to divide the target sub-region based on the terrain position index, taking the same target radius range R as a unit, first divide the land to be evaluated into multiple sub-regions, and then apply the aforementioned terrain position index calculation formula to calculate the terrain position index of each sub-region , and determine the target gradient where each sub-region is located according to the numerical interval where the terrain position index corresponding to each sub-region is located.

[0063] In some specific embodiments, the terrain of the central Yunnan urban agglomeration in the east-central region of Yunnan Province is the area to be studied, and its terrain position index is between 0 and 1.22. It is divided into five gradient levels: I (0 - 0.40), II (0.40 - 0.53), III (0.53 - 0.63), IV (0.63 - 0.74), and V (0.74 - 1.22). When the value of the terrain position index corresponding to the sub-region is within the above corresponding interval, it can be determined which target sub-interval corresponding to which target gradient the sub-region belongs to.

[0064] S20, analyze the target sub-region from two evaluation dimensions: the terrain gradient effect dimension and the land gradient utilization characteristic dimension, and determine the land change degree evaluation result of the land to be evaluated based on the terrain gradient effect evaluation results and land gradient utilization characteristic dimension evaluation results of the obtained multiple target sub-regions.

[0065] In this embodiment, after dividing the land to be evaluated into multiple target sub-regions with different target gradients based on the terrain position index, the target sub-region is analyzed from two evaluation dimensions: the terrain gradient effect dimension and the land gradient utilization characteristic dimension.

[0066] The terrain gradient effect means that the land type is significantly affected by the height of the soil body, and thus the land type is significantly distributed in a stepped manner. Analyzing from the terrain gradient effect dimension can analyze the spatio-temporal pattern change characteristics of the land area to be studied, and thus reasonably and effectively reveal the gradient distribution characteristics of land use affected by the terrain.

[0067] The characteristics of land gradient utilization refer to the dynamic characteristics reflecting the land gradient utilization changes in the land area to be studied. The land gradient utilization change is the result of the combined action of natural and socio-economic factors. There are significant differences in the driving factors and their contribution intensities for different land use types. Analyzing the land from the dimension of land gradient utilization characteristics can lay a foundation for the subsequent analysis of the carbon emission effect of the land, so as to reasonably regulate the carbon emissions in the land area to be studied and predict the future land change trend.

[0068] In the technical solution provided in this embodiment, in order to accurately evaluate a complex land area, first, the terrain position index calculated by using the elevation value and the slope value is used to divide the land to be evaluated into multiple target sub-regions with different target gradients; after evaluating the terrain gradient effect and the land gradient utilization characteristics of each target sub-region, the evaluation result of the land change degree of the land to be evaluated is comprehensively obtained, realizing the accurate evaluation of the complex land area, and providing an analysis basis for the subsequent research and regulation of the carbon emission effect of the complex land area.

[0069] Second Embodiment

[0070] In this embodiment, based on any one of the embodiments, the dimension of land gradient utilization characteristics includes the area change of land use types, and in this embodiment, the land use transfer matrix is used to quantify the area change of land use types of the land to be evaluated.

[0071] The land use transfer matrix originates from the quantitative description of the system state and state transfer in system analysis and is the application of the Markov model in the field of land use change. The land use transfer matrix can not only clearly display the area information of land use types in each period of the research area, but also reflect the transferred-in and transferred-out areas of different land types at the initial and final stages of the research. Therefore, in this embodiment, the land use transfer matrix is used to analyze the area change of land use types of the land to be evaluated.

[0072] Specifically, the land area of each target sub-region with different target gradients is obtained, and the land use transfer matrix of the land to be evaluated is constructed according to the land area of each target sub-region. Among them, the calculation expression of the land use transfer matrix is:

[0073]

[0074] In the formula, is the land use transfer matrix, that is, The area of the land type converted to land type; represents the land area under different gradient levels; are the land type codes before and after the transfer.

[0075] After obtaining the land use transfer matrix, the area change of the land use type of the land to be evaluated in the historical period is analyzed based on the land use transfer matrix.

[0076] The following is an example of an analysis of the area changes of land use types:

[0077] In this example, the terrain of the Central Yunnan Urban Agglomeration in the eastern and central regions of Yunnan Province from 2000 to 2020 is used as the land to be evaluated. Based on the land use transfer matrix constructed above, the land gradient use type transfer characteristics of the Central Yunnan Urban Agglomeration terrain are analyzed for the area change of land use types. In this example, the terrain of the Central Yunnan Urban Agglomeration is divided into five gradient levels: I (0~0.40), II (0.40~0.53), III (0.53~0.63), IV (0.63~0.74) and V (0.74~1.22).

[0078] Reference Figure 2 A schematic diagram of the transfer of land gradient utilization types in the central Yunnan urban agglomeration between 2000 and 2020 is shown. In the figure, a represents the proportion of the conversion area of ​​each land use type in the area of ​​gradient level I, b represents the proportion of the conversion area of ​​each land use type in the area of ​​gradient level II, c represents the proportion of the conversion area of ​​each land use type in the area of ​​gradient level III, d represents the proportion of the conversion area of ​​each land use type in the area of ​​gradient level IV, and e represents the proportion of the conversion area of ​​each land use type in the area of ​​gradient level V.

[0079] From 2000 to 2020, the land use types in the land use gradient of the central Yunnan urban agglomeration shifted significantly, and were interchanged within the same gradient. The trajectories of area change in various types of land use were significantly different, and the types of transformation showed diversified characteristics. With the increase of the gradient level, the areas of cultivated land, water areas, urban land, rural settlements, industrial and mining, and transportation construction land continued to decrease, the areas of forest land and unused land continued to increase, and the area of ​​grassland showed an increase-decrease-increase trend.

[0080] In the level I gradient, the mutual conversion of land types is active, with the overall performance of the outflow of cultivated land as the main one, followed by grassland, and then forest land. The outflow of urban land, industrial and mining and transportation construction land and unused land is the smallest. The cultivated land area has been continuously reduced in the past 20 years, and the reduced cultivated land has been mainly converted into urban land, rural settlements, and industrial and mining and transportation construction land. The grassland area has decreased overall, and the reduced grassland has been mainly converted into cultivated land, and part of it has been converted into forest land. The forest area has decreased overall, and the reduced forest land has been mainly converted into cultivated land and grassland.

[0081] In the second - level gradient, the transfer of land use types is mainly the transfer out of grasslands and forestlands. The main flow direction of grasslands is to cultivated land and forestland, and the main flow direction of forestlands is to cultivated land and grassland. With population growth, the demand for agricultural products such as food and livestock is increasing continuously. Grasslands and forestlands are reclaimed into cultivated land to meet the survival needs of the population. The mutual transfer between forestland and grassland is not only the result of natural succession but also affected by human activities such as deforestation and grass planting. At this gradient level, both the outflow and inflow of cultivated land are obvious, and the transfer - in and transfer - out volumes are basically the same. The transferred - in area of urban land, industrial and mining, and transportation construction land is much higher than the transferred - out area. This also indicates that the urbanization expansion speed is fast at this gradient level, and the demand for urban construction, industrial, and transportation infrastructure construction land is large.

[0082] In the third - level gradient, the areas of cultivated land, forestland, and grassland are significantly transferred out, and the remaining land use types are the main transferred - in areas. Grassland, cultivated land, and forestland are the top three land types in terms of transfer area, and the flow direction is mainly the mutual transfer between these three land use types. Water areas, urban land, rural settlements, industrial and mining, and transportation construction land, and unused land are land use types with more transferred - in than transferred - out, and the total area has increased. The overall water area in the central Yunnan urban agglomeration has increased; the areas of urban land, rural settlements, industrial and mining, and transportation construction land have increased, and the increased areas of these four land use types mainly come from cultivated land, forestland, and grassland. The area of unused land has increased, mainly from cultivated land and grassland.

[0083] In the fourth - level gradient, the proportion of forestland area exceeds 50%, and the areas of the other seven land use types have decreased significantly. At this gradient level, forestland, grassland, and cultivated land are the three most active land use types in terms of area transfer. Forestland is mainly converted into grassland, and secondly into cultivated land. Grassland is mainly converted into forestland and cultivated land. Cultivated land is mainly transferred out to forestland and grassland. The areas of water areas, urban land, rural settlements, industrial and mining, and transportation construction land, and unused land have decreased significantly, and the transfer intensity has weakened. The terrain in high - gradient areas is complex, and steep mountains limit the development and utilization of land, resulting in a natural reduction in the area of land type transfer.

[0084] In the fifth - level gradient, the transfer intensity of each land type decreases, and the transformation between different land types is more uniform than in other gradients. The transformation of forestland to other land use types is the most obvious, and the main flow direction is to grassland and cultivated land. Grassland also shows obvious transfer behavior, and the main flow direction is to forestland, and secondly to cultivated land. The transfer behavior of cultivated land varies in different regions. The main transferred - in land use type is forestland, and the main transferred - out land use types are forestland and grassland. From the transformation trajectory, the mutual transformation behavior between land types at this gradient level lacks vitality, and the transferred - in and transferred - out areas of the five land use types, namely water areas, urban land, rural settlements, industrial and mining, and transportation construction land, and unused land, have decreased, and the diversity of transformation types has weakened.

[0085] The third embodiment

[0086] In this embodiment, based on any one of the embodiments, the land gradient utilization feature dimension includes the change trend of the land gradient utilization degree, and in this embodiment, the land utilization degree change rate is used to quantify the change trend of the land gradient utilization degree in the land to be evaluated.

[0087] Specifically, calculate the land comprehensive utilization degree indexes of the target sub-region in two different historical periods respectively, obtain the first land comprehensive utilization degree index and the second land comprehensive utilization degree index, and calculate the land utilization degree change rate of the target sub-region according to the first land comprehensive utilization degree index and the second land comprehensive utilization degree index, so as to analyze the change trend of the land gradient utilization degree in the land to be evaluated based on the land utilization degree change rates of the respective target sub-regions.

[0088] In this embodiment, the calculation expression of the land comprehensive utilization degree index is:

[0089]

[0090] In the formula, represents the land utilization degree change rate, is the land gradient utilization degree classification index, is the proportion of the land gradient utilization degree classification area;

[0091] The larger the value, the higher the land development and utilization degree of the area, and vice versa.

[0092] In this embodiment, the calculation expression of the land utilization degree change rate is:

[0093]

[0094] In the formula, R is the land utilization degree change rate, is the first land comprehensive utilization degree index, is the second land comprehensive utilization degree index, and a and b represent two different historical periods.

[0095] If R > 0, it indicates that the land to be evaluated is in the development period; if R < 0, it is in the adjustment period.

[0096] It should be noted that the land utilization degree change rate usually compares the land comprehensive utilization degree index calculated in a relatively far historical period with the land comprehensive utilization degree index calculated in a relatively recent historical period in research. Therefore, the time period corresponding to the first land comprehensive utilization degree index is later than the time period corresponding to the second land comprehensive utilization degree index.

[0097] Exemplarily, in a specific implementation manner, the values of the land gradient utilization degree classification index can be referred to as shown in Table 1 below.

[0098] Table 1. Grading Assignment Table for the Degree of Land Gradient Utilization

[0099]

[0100] After obtaining the land use degree change rate, based on the land use degree change rate of each target sub-region, analyze the change trend of the land gradient utilization degree in the land to be evaluated.

[0101] The following takes an example to illustrate the analysis of the change trend of the land gradient utilization degree:

[0102] Exemplarily, in this example, the terrain of the Central Yunnan Urban Agglomeration in the central and eastern regions of Yunnan Province from 2000 to 2020 is also used as the land to be evaluated. Based on the constructed land use transfer matrix above, analyze the area change of the land use type in the transfer characteristics of the land gradient utilization type of the terrain of the Central Yunnan Urban Agglomeration. In this example, the terrain of the Central Yunnan Urban Agglomeration is divided into 5 gradient levels: I (0 - 0.40), II (0.40 - 0.53), III (0.53 - 0.63), IV (0.63 - 0.74), and V (0.74 - 1.22).

[0103] Table 2. Land Gradient Utilization Degree of the Central Yunnan Urban Agglomeration from 2000 to 2020

[0104]

[0105] Referring to Table 2, subtract the index in 2000 from the comprehensive index of land use degree in 2020 in Table 2 to obtain the change of the land development and utilization degree of the Central Yunnan Urban Agglomeration in the past 20 years.

[0106] From 2000 to 2020, the overall degree of land gradient utilization in the central Yunnan urban agglomeration showed a continuous upward trend, indicating that the intensity of human activity interference and the degree of land development and utilization in the study area have been continuously increasing. With the increase of the gradient level, the comprehensive index of land gradient utilization decreased, showing a trend from strong to weak, indicating that the degree of land development and utilization is significantly restricted by the terrain gradient, and it is difficult to develop land in high-gradient areas. In the I-level gradient, the comprehensive index of land gradient utilization is the largest, increasing from 204.08 in 2000 to 215.36 in 2020, and the change rate of land gradient utilization is as high as 2.4%. This indicates that the land development degree of this gradient is high. During the process of urbanization promotion, the demand for land resources in the central Yunnan urban agglomeration is increasing, which promotes the increase of the degree of land development and utilization in low-gradient areas. The degree of land development and utilization in the II-level gradient has slowed down, and the maximum comprehensive index of land gradient utilization is 166.12. The change rates of land gradient utilization within the I-II level gradient range are all positive, indicating that the corresponding areas in this range were in a continuous development period from 2000 to 2020. A large amount of land was used for agriculture, industry and urban development, and the expansion of the land use scale further increased the degree of land development. In the III-V level gradients, the comprehensive index of land gradient utilization showed a fluctuating change trend of decreasing-increasing-decreasing. The change of land gradient utilization has successively experienced stages such as an adjustment period, a development period and an adjustment period. From 2000 to 2005, the economic and social development of the central Yunnan urban agglomeration was relatively slow. Although the land demand was large, it was difficult and costly to develop land in high-gradient areas, and the development was concentrated in areas with relatively flat terrain. From 2005 to 2015, the urbanization development accelerated, and the demand for industrial and commercial land increased. The central Yunnan urban agglomeration began to "move towards the mountains and slopes" and build mountain towns.

[0107] Visualize the data in Table 1 and draw the spatial distribution map of the change in the degree of land gradient utilization in the central Yunnan urban agglomeration from 2000 to 2020 as shown in Figure 3 Figure

[0108] As can be easily seen from the figures, the degree of land development and utilization in the central Yunnan urban agglomeration has changed significantly. The degree of land use has increased in most areas, and the areas with a large increase in the degree of gradient land use mainly show a cluster-like agglomeration feature, distributed in the eastern and southern regions; the areas with a small increase are sporadically distributed in the northern and western regions, generally maintaining a spatial pattern of "high in the east and low in the west, high in the south and low in the north", which is opposite to the topographic and geomorphic pattern of the central Yunnan urban agglomeration. The areas with relatively small altitudes and gentle slopes have the highest degree of development; on the contrary, the development degree is low. In terms of the internal change range of the region, the areas with the largest change in the degree of gradient land use are mainly distributed in the main urban area of Kunming, the jurisdiction areas of Yuxi City, the jurisdiction areas of Qujing City, Luliang County, Shizong County, Luoping County, the central part of Chuxiong Prefecture, and 7 counties and cities in Honghe Prefecture. The added value of the degree of gradient land use reaches 11.28. The areas with a relatively large change in the degree of gradient land use mainly surround the areas with the largest increase, forming a decreasing distribution in circles. The added value of the degree of gradient land use is 5.57. The areas with a medium level of change in the degree of gradient land use are widely distributed in terms of area, and the added value of the degree of gradient land use is 1.17. The areas with a relatively small change in the degree of gradient land use are concentrated and contiguous in the northern, northwestern, and southwestern regions. The change value of the degree of gradient land use from 2000 to 2020 is 0.03. The areas with the smallest change in the degree of gradient land use are interspersed with the areas with a relatively low change, appearing in the northern region with relatively complex topographic and geomorphic conditions. Such natural conditions have limited large-scale development and construction activities to a certain extent.

[0109] Fourth Embodiment

[0110] In this embodiment, based on any one of the embodiments, the dimension of the gradient land use feature includes the change situation of the gradient land use structure, and in this embodiment, the information entropy and / or the equilibrium degree index are used to quantify the change situation of the gradient land use structure in the land to be evaluated.

[0111] Specifically, calculate the information entropy of the target sub-region, and calculate the equilibrium degree index of the target sub-region according to the information entropy.

[0112] In this embodiment, the information entropy is an important index reflecting the orderliness and diversity of the regional land use structure. The higher the information entropy value, the lower the orderliness degree of the land use structure, the smaller the difference in the areas of each land type, and the more stable the land use structure. The calculation expression of the information entropy is:

[0113]

[0114] If the region is in the stage of not yet developed, the information entropy value is the smallest ( = 0); if the region is developed and mature, and each land use type tends to be stable, then the information entropy is the largest ( = ).

[0115] In this embodiment, the balance index can be used to reflect the comparability of different land use types at different times and the homogeneity of land use. The calculation expression of the balance index is as follows:

[0116]

[0117] In the formula, represents the information entropy; represents the balance index, is the proportion of the area of each land type under the same target gradient to the total land area of the target gradient; n is the number of land use types.

[0118] The larger the balance index, the stronger the homogeneity of land gradient utilization in the central Yunnan urban agglomeration.

[0119] In this embodiment, after obtaining the change rate of land use degree, based on the information entropy and / or balance index of each target sub-region, analyze the change situation of the land gradient utilization structure in the land to be evaluated. The change situation of the land gradient utilization structure includes the stability of the land use structure and the homogeneity of land gradient utilization.

[0120] The following is an example to illustrate the analysis of the change situation of the land gradient utilization structure:

[0121] Exemplarily, in this example, the terrain of the central Yunnan urban agglomeration in the central and eastern regions of Yunnan Province from 2000 to 2020 is also used as the land to be evaluated, and the area change situation of the land use types is analyzed based on the constructed land use transfer matrix for the transfer characteristics of the land gradient utilization types of the terrain of the central Yunnan urban agglomeration. In this example, the terrain of the central Yunnan urban agglomeration is divided into 5 gradient levels: I (0 - 0.40), II (0.40 - 0.53), III (0.53 - 0.63), IV (0.63 - 0.74), and V (0.74 - 1.22).

[0122] Table 3. Land Gradient Utilization Structure Index of the Central Yunnan Urban Agglomeration from 2000 to 2020

[0123]

[0124] Referring to Table 3 above, from 2000 to 2020, the information entropy and equilibrium degree index of land gradient utilization in the central Yunnan urban agglomeration showed an overall upward trend, indicating that the land use structure in the study area has changed significantly, its orderliness is constantly increasing, and the land distribution has become more balanced. Further sorting out found that there are significant differences in the land use structure gradient in the central Yunnan urban agglomeration in the past 20 years. As the gradient level increases, the information entropy and equilibrium degree index decrease, the area differences of various land use types at different gradient levels increase, the homogeneity of the land use structure weakens, and the stability of the land gradient utilization structure decreases. On the one hand, during the research period, the information entropy and equilibrium degree index of the I-level gradient remained the highest, indicating that the land use types are balanced and diverse at this gradient level, and the areas of various land classes are relatively close. This also means that the land resources at this gradient are effectively utilized and managed, and the social, economic and environmental benefits of the land are relatively high. Compared with other gradient levels, the information entropy and equilibrium degree index of the V-level gradient are the smallest, indicating that there are large differences in the scale of various land classes at this gradient, showing a situation where forest land occupies a dominant position and the areas of other land use types are relatively small. This also reveals the singularity and imbalance of land resource utilization in high-gradient areas, which may lead to instability of the regional ecological environment if it continues for a long time. On the other hand, from 2000 to 2020, there are differences in the dynamic trends of the information entropy and equilibrium degree index of the land use structure at different gradient levels. During the research period, the information entropy and equilibrium degree index of the I-III level gradients remained increasing. The information entropy and equilibrium degree index of the IV-V level gradients did not change before 2005 and then began to increase, but the increase amplitude is much smaller than that of the low-gradient areas. This shows that there are significant differences in the intensity of land development and utilization at different gradient levels in the past 20 years. The land use structure in the low-gradient areas is more balanced. Although the land development in the high-gradient areas is difficult, due to the reality of land shortage, the current situation of land resource utilization and management in the high-gradient areas has been improved, and the balance of the land use structure is increasing.

[0125] Fifth Embodiment

[0126] In this embodiment, based on any one of the embodiments, the topographic gradient effect dimension includes at least one of elevation value, slope value, topographic relief degree, and distribution index.

[0127] Considering the profound impact of topographic factors on land use, in this embodiment, four key topographic factors, namely elevation, slope, topographic relief degree, and distribution index, are selected to deeply analyze the topographic gradient effect of the land to be evaluated.

[0128] Elevation is an important indicator reflecting the topographic characteristics of the region. Optionally, in some embodiments, elevation is superimposed with land use to analyze the area change characteristics of different land classes when the elevation increases by 100m;

[0129] Slope is an important characteristic of mountains, representing the inclination degree of surface units. Slope has a huge impact on agricultural production, social and economic development, and the ecological environment. Optionally, in some embodiments, the slope can be overlaid with land use to analyze the area change characteristics of each land type when the slope increases by 1°.

[0130] The terrain undulation degree can intuitively reflect the terrain undulation characteristics of a region and is a quantitative index for describing landform patterns and classifying landform types. Optionally, in some embodiments, the terrain undulation degree can be overlaid with land use to further analyze the area change characteristics of each land type when the terrain undulation degree increases by 50m.

[0131] The distribution index is mostly used to describe the distribution of different land use types in different terrain gradients in the study area. It can effectively eliminate the influence brought by terrain sections and land use area differences and represent the distribution advantage status of different land types. Optionally, in some embodiments, the distribution index is combined with the terrain position index to comprehensively analyze the distribution of land use types in different terrain gradients.

[0132] In addition, as an implementation solution, Figure 4 is a schematic architecture diagram of the hardware operating environment of the computer system involved in the solution of the embodiment of the present application.

[0133] As Figure 4 shown, the computer system may include: a processor 1001, such as a CPU, a memory 1005, a user interface 1003, a network interface 1004, and a communication bus 1002. Among them, the communication bus 1002 is used to realize the connection and communication between these components. The user interface 1003 may include a display screen (Display) and an input unit such as a keyboard (Keyboard). Optionally, the user interface 1003 may further include a standard wired interface and a wireless interface. The network interface 1004 may optionally include a standard wired interface and a wireless interface (such as a WI-FI interface). The memory 1005 may be a high-speed RAM memory or a stable memory (non-volatile memory), such as a disk memory. The memory 1005 may optionally also be a storage device independent of the aforementioned processor 1001.

[0134] Those skilled in the art can understand that Figure 4 the computer system architecture shown in

[0135] As Figure 4As shown in the figure, the memory 1005 as a storage medium may include an operating system, a network communication module, a user interface module, and a land change degree evaluation program based on gradient division and two-dimensional analysis. Among them, the operating system is a program that manages and controls the hardware and software resources of a computer system, and runs the land change degree evaluation program based on gradient division and two-dimensional analysis, as well as other software or programs.

[0136] In Figure 4 In the computer system shown in the figure, the user interface 1003 is mainly used to connect to a terminal and communicate with the terminal for data; the network interface 1004 is mainly used to connect to a background server and communicate with the background server for data; the processor 1001 can be used to call the land change degree evaluation program stored in the memory 1005 based on gradient division and two-dimensional analysis.

[0137] In this embodiment, the computer system includes: a memory 1005, a processor 1001, and a land change degree evaluation program stored on the memory and executable on the processor, where:

[0138] When the processor 1001 calls the land change degree evaluation program stored in the memory 1005 based on gradient division and two-dimensional analysis, the following operations are performed:

[0139] The land to be evaluated is divided into target sub-regions with multiple different target gradients by using the topographic position index; wherein, the topographic position index is calculated from the elevation value and slope value of the land.

[0140] The target sub-regions are analyzed from two evaluation dimensions: the topographic gradient effect dimension and the land gradient utilization feature dimension, and based on the obtained topographic gradient effect evaluation results and land gradient utilization feature dimension evaluation results of the multiple target sub-regions, the land change degree evaluation result of the land to be evaluated is determined.

[0141] When the processor 1001 calls the land change degree evaluation program stored in the memory 1005 based on gradient division and two-dimensional analysis, the following operations are performed:

[0142] Taking the target radius range as a unit, the land to be evaluated is divided into multiple sub-regions;

[0143] Calculate the topographic position index corresponding to each of the sub-regions;

[0144] According to the numerical interval where the topographic position index corresponding to each of the sub-regions is located, determine the target gradient where each of the sub-regions is located;

[0145] The sub-regions in the same target gradient are determined as the target sub-regions composed of one or more of the sub-regions.

[0146] When the processor 1001 calls the land change degree evaluation program stored in the memory 1005 based on gradient division and two-dimensional analysis, the following operations are performed:

[0147] Select any pixel in the land to be evaluated as the target pixel in pixel units. Centering on the target pixel, take the average of the elevation values and slope values of all pixels within the target radius to obtain the average elevation value and average slope value of the target pixel;

[0148] Based on the elevation value, slope value of the target pixel, as well as the average elevation value and the average slope value, calculate the topographic position index within the target radius:

[0149]

[0150] In the formula, is the local window topographic position index of the pixel in the i-th row and j-th column under the local window of the target radius range R; is the local window centered on the target pixel at the (i, j) position, and are the elevation value and slope value of the target pixel respectively, is the average elevation value, is the average slope value.

[0151] When the processor 1001 calls the land change degree evaluation program stored in the memory 1005 based on gradient division and two-dimensional analysis, the following operations are performed:

[0152] Obtain the land type areas of the target sub-regions with different target gradients, construct the land use transfer matrix of the land to be evaluated according to the land type areas of each target sub-region, and analyze the area change of the land use types in the land to be evaluated during the historical period based on the land use transfer matrix;

[0153] When the processor 1001 calls the land change degree evaluation program stored in the memory 1005 based on gradient division and two-dimensional analysis, the following operations are performed:

[0154] Calculate the comprehensive land use degree indexes of the target sub-region in two different historical periods respectively to obtain the first comprehensive land use degree index and the second comprehensive land use degree index, and calculate the land use degree change rate of the target sub-region according to the first comprehensive land use degree index and the second comprehensive land use degree index, so as to analyze the land gradient use degree change trend in the land to be evaluated based on the land use degree change rates of each target sub-region;

[0155] When the processor 1001 calls the land change degree evaluation program stored in the memory 1005 based on gradient division and two-dimensional analysis, the following operations are performed:

[0156] Calculate the information entropy of the target sub-region, and calculate the equilibrium degree index of the target sub-region according to the information entropy, so as to analyze the land gradient utilization structure change situation of the land to be evaluated based on the information entropy and / or the equilibrium degree index of each target sub-region. The land gradient utilization structure change situation includes the stability of the land use structure and the homogeneity of the land gradient utilization.

[0157] In addition, those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program includes program instructions, and the computer program can be stored in a storage medium, and the storage medium is a computer-readable storage medium. The program instructions are executed by at least one processor in the computer system to implement the process steps of the embodiments of the above methods.

[0158] Therefore, the present application also provides a computer-readable storage medium, which stores a land change degree evaluation program based on gradient division and two-dimensional analysis. When the land change degree evaluation program based on gradient division and two-dimensional analysis is executed by a processor, it implements each step of the land change degree evaluation method based on gradient division and two-dimensional analysis as described in the above embodiments.

[0159] Among them, the computer-readable storage medium can be various computer-readable storage media such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a magnetic disk, or an optical disc that can store program codes.

[0160] It should be noted that since the storage medium provided in the embodiments of the present application is the storage medium used for implementing the methods of the embodiments of the present application, those skilled in the art can understand the specific structure and deformation of the storage medium based on the methods introduced in the embodiments of the present application, so it will not be elaborated here. Any storage medium used in the methods of the embodiments of the present application belongs to the scope to be protected by the present application.

[0161] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0162] This application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams can be implemented by computer program instructions, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can also be implemented. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0163] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means implement the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0164] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0165] It should be noted that in the claims, any reference signs placed between parentheses shall not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. This application can be implemented by means of hardware including several different components and by means of a suitably programmed computer. In a unit claim listing several apparatuses, several of these apparatuses can be embodied by the same item of hardware. The use of the words first, second, and third, etc. does not denote any order. These words can be interpreted as names.

[0166] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0167] Obviously, those skilled in the art can make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalent technologies, this application is also intended to include these changes and modifications.

Claims

1. A land change degree assessment method based on gradient division and two-dimensional analysis, characterized in that: The method comprises the following steps: The land to be evaluated is divided into a plurality of target sub-areas with different target gradients by using a terrain index; wherein the terrain index is calculated by the elevation value and slope value of the land; Analyze the target sub-area from two evaluation dimensions: terrain gradient effect dimension and land gradient utilization characteristic dimension, and determine the land change degree evaluation result of the land to be evaluated based on the terrain gradient effect evaluation results and land gradient utilization characteristic dimension evaluation results of the obtained multiple target sub-areas; The step of dividing the land to be evaluated into a plurality of target sub-areas with different target gradients by using the terrain index specifically includes: Taking the target radius range as a unit, dividing the land to be assessed into a plurality of sub-areas; Calculating the terrain index corresponding to each of the sub-areas; Determining the target gradient of each sub-region according to the numerical range of the terrain index corresponding to each sub-region; The sub-regions in the same target gradient are determined as the target sub-region composed of one or more sub-regions.

2. The land change degree assessment method based on gradient division and two-dimensional analysis according to claim 1, characterized in that: The elevation value and the slope value are obtained through the digital elevation model data of the land to be evaluated, and the calculation steps of the terrain index include: Select any pixel in the land to be evaluated as a target pixel in units of pixels, take the target pixel as the center, take the average of the elevation values ​​and slope values ​​of all pixels within the target radius, and obtain the average elevation value and average slope value of the target pixel; Based on the elevation value and slope value of the target pixel, as well as the average elevation value and the average slope value, the terrain index within the target radius is calculated: ； In the formula, is the local window topographic index of the pixel in the i-th row and j-th column in the local window of the target radius range R; is a local window centered at the target pixel at position (i, j), and are the elevation and slope values ​​of the target pixel, respectively. is the average elevation value, is the average slope value.

3. The land change degree assessment method based on gradient division and two-dimensional analysis according to claim 1, characterized in that: The land gradient utilization characteristic dimension includes at least one of the three dimensions of area change of land use type, change trend of land gradient utilization degree and change of land gradient utilization structure. The evaluation results of the land gradient utilization characteristic dimension include: Obtaining the land use area of ​​each target sub-region with different target gradients, and constructing a land use transfer matrix of the land to be evaluated according to the land use area of ​​each target sub-region, so as to analyze the area change of the land use type of the land to be evaluated in the historical period based on the land use transfer matrix; Calculate the comprehensive land utilization index of the target sub-region in two different historical periods respectively to obtain a first comprehensive land utilization index and a second comprehensive land utilization index; calculate the land utilization change rate of the target sub-region according to the first comprehensive land utilization index and the second comprehensive land utilization index, so as to analyze the land gradient utilization change trend in the land to be evaluated based on the land utilization change rate of each target sub-region; Calculate the information entropy of the target sub-region, and calculate the balance index of the target sub-region according to the information entropy, so as to analyze the changes in the land gradient utilization structure of the land to be evaluated based on the information entropy and / or the balance index of each target sub-region, wherein the changes in the land gradient utilization structure include the stability of the land utilization structure and the homogeneity of the land gradient utilization.

4. The land change degree assessment method based on gradient division and two-dimensional analysis according to claim 3 is characterized in that: The calculation expression of the land use transfer matrix is: ； In the formula, is the land use transfer matrix, that is Land type conversion The area of ​​the land type; Indicates the land area at different gradient levels; Class codes before and after the transfer.

5. The land change degree assessment method based on gradient division and two-dimensional analysis as claimed in claim 3, characterized in that: The calculation expression of the comprehensive land utilization index is: ； In the formula, represents the rate of change of land use degree, is the land gradient utilization degree classification index, The percentage of land use gradient classification area; The calculation expression of the land use change rate is: ； In the formula, R is the rate of change of land use degree, is the first land comprehensive utilization index, is the second comprehensive land utilization index, and a and b represent two different historical periods.

6. The land change degree assessment method based on gradient division and two-dimensional analysis according to claim 3 is characterized in that: The calculation expression of the information entropy is: ； The calculation expression of the balance index is: ； In the formula, represents information entropy; represents the balance index, It is the proportion of each land type area under the same target gradient to the total land area of ​​the target gradient; n is the number of land use types.

7. The land change degree assessment method based on gradient division and two-dimensional analysis according to claim 1, characterized in that: The terrain gradient effect dimension includes at least one of an elevation value, a slope value, a terrain relief and a distribution index.

8. A computer system, characterized in that: The computer system includes: a memory, a processor, and a land gradient utilization change assessment program stored in the memory and executable on the processor. When the land gradient utilization change assessment program is executed by the processor, the steps of the land change degree assessment method based on gradient division and two-dimensional analysis as described in any one of claims 1 to 7 are implemented.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a land gradient utilization change assessment program, which, when executed by a processor, implements the steps of a land change degree assessment method based on gradient division and two-dimensional analysis as described in any one of claims 1 to 7.

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