Gradient division and two-dimensional analysis-based land change degree evaluation method and system, and storage medium

Abstract

The invention relates to the technical field of land utilization change evaluation, in particular to a land change degree evaluation method and system based on gradient division and two-dimensional analysis and a storage medium. Dividing the to-be-evaluated land into a plurality of target sub-regions with different target gradients by adopting topographic position indexes; wherein the terrain position index is obtained by calculating an elevation value and a slope value of the land; and analyzing the target sub-regions from two evaluation dimensions including a terrain gradient effect dimension and a land gradient utilization characteristic dimension, and determining a land change degree evaluation result of the to-be-evaluated land based on the obtained terrain gradient effect evaluation result and the land gradient utilization characteristic dimension evaluation result of the plurality of target sub-regions. The objective of the invention is to solve the problem of how to carry out land utilization change evaluation on areas with obvious vertical zone performance and altitude gradient performance.

Description

Technical Field

[0001] The present application relates to the technical field of land use change evaluation, and in particular 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 man and nature. As a manifestation of the high and low forms of the surface, topography drives resource distribution and human activities through the migration and energy conversion of surface materials, and determines the formation of the national spatial pattern. Clarifying the role of topography in the development and utilization of national space is the basis and premise for analyzing the carbon emission effect of land gradient utilization and its regulation.

[0003] In the relevant technical scheme, the Chinese patent with application number CN202111363830.7 discloses a method for evaluating land use changes in mountainous areas based on terrain gradients, which mainly includes four steps: quantifying terrain gradients, building an evaluation system, collecting and analyzing original data, and generating evaluation results. It systematically explores the terrain differentiation characteristics and change laws of land use in mountainous areas from the perspectives of altitude, slope, terrain position, etc., and constructs a land use vertical gradient index based on administrative units to deeply characterize the local characteristics of vertical land use differentiation.

[0004] However, the calculation of the terrain index in the land use change evaluation in the above technical solution is based on the traditional calculation of the entire study area, and only a single land use dynamic degree is used to evaluate the land use change. This evaluation method is used in areas with obvious vertical zonality and altitude gradients, such as the eastern and central regions of Yunnan, where multiple land types such as cultivated land, forest land, grassland, water area and urban land are significantly affected by altitude, and there is a problem of inaccurate land use change evaluation.

[0005] In view of this, there is a need for a land change degree assessment method that can meet the needs of accurate land use change assessment for complex land. Summary of the invention

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

[0007] To achieve the above objectives, the present application provides a land change degree assessment method based on gradient division and dual-dimensional analysis, the method comprising:

[0008] 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;

[0009] The target sub-area is analyzed from two evaluation dimensions: terrain gradient effect dimension and land gradient utilization characteristic dimension, and based on the terrain gradient effect evaluation results and land gradient utilization characteristic dimension evaluation results of multiple target sub-areas obtained, the land change degree evaluation results of the land to be evaluated are determined.

[0010] Optionally, 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:

[0011] Taking the target radius range as a unit, dividing the land to be assessed into a plurality of sub-areas;

[0012] Calculating the terrain index corresponding to each of the sub-areas;

[0013] Determining the target gradient of each sub-region according to the numerical range of the terrain index corresponding to each sub-region;

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

[0015] Optionally, the elevation value and the slope value are obtained through digital elevation model data of the land to be evaluated, and the step of calculating the terrain index includes:

[0016] 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;

[0017] 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:

[0018]

[0019] 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.

[0020] Optionally, 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:

[0021] 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;

[0022] 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;

[0023] 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.

[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 Land type conversion The area of ​​the land type; Indicates the land area at different gradient levels; Class codes before and after the transfer.

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

[0028]

[0029] 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;

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

[0031]

[0032] 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.

[0033] Optionally, the information entropy is calculated as follows:

[0034]

[0035] The calculation expression of the balance index is:

[0036]

[0037] 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.

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

[0039] In addition, to achieve the above-mentioned purpose, the present application also provides a computer system, which includes: a memory, a processor, and a land gradient utilization change assessment program stored in the memory and executable on the processor, wherein the land gradient utilization change assessment program, when executed by the processor, implements the steps of the land change degree assessment method based on gradient division and two-dimensional analysis as described in any one of the above items.

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

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

[0042] 1. The terrain index calculated by elevation and slope values ​​is used to divide the land to be evaluated into multiple target sub-areas with different target gradients. After evaluating the terrain gradient effect and land gradient utilization characteristics of each target sub-area, the land change degree assessment results of the land to be evaluated are comprehensively obtained, so as to achieve accurate assessment of complex land areas and provide an analytical basis for subsequent research and regulation of carbon emission effects in complex land areas.

[0043] 2. By introducing gradient levels to divide the land to be evaluated, the land use characteristics in the vertical direction are analyzed, and the land use distribution and changes at different gradient levels are analyzed. Not only the overall impact of terrain on land use is considered, but also the spatial distribution and spatial change characteristics of different land use types under the condition of vertical differentiation and gradient stratification of land are deeply analyzed, so as to achieve accurate evaluation of land areas with obvious vertical zonality and altitude gradient. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a flow chart of the first embodiment of the land change degree assessment method based on gradient division and dual-dimensional analysis of the present application;

[0045] Figure 2 This is a schematic diagram of the land gradient utilization type transfer of the central Yunnan urban agglomeration between 2000 and 2020 involved in the embodiment of the present application;

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

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

[0048] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0049] In order to better understand the above technical solution, exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0050] First embodiment

[0051] Reference Figure 1In this embodiment, the land change degree assessment method based on gradient division and dual-dimensional analysis includes the following steps:

[0052] S10, using a terrain index to divide the land to be evaluated into a plurality of target sub-areas with different target gradients; wherein the terrain index is calculated based on the elevation value and slope value of the land;

[0053] In this embodiment, the traditional evaluation method often uses the entire land to be evaluated as a reference, but for complex land areas, it cannot reflect the terrain differences between local areas. Therefore, this embodiment proposes to use the terrain position index to divide the entire land to be evaluated.

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

[0055] Optionally, the steps for calculating the terrain position index in this embodiment are as follows:

[0056] Step S11, selecting any pixel in the land to be evaluated as a target pixel in units of pixels, taking the target pixel as the center, taking the average of the elevation values ​​and slope values ​​of all pixels within the target radius, and obtaining the average elevation value and average slope value of the target pixel;

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

[0058]

[0059] 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.

[0060] Optionally, the elevation value and the slope value in the embodiment can be obtained through digital elevation model (DEM) data.

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

[0062] Optionally, how to use the terrain-based bit index Divide the target sub-area into multiple sub-areas with the same target radius R as the unit, and then apply the terrain index calculation formula to calculate the terrain index of each sub-area. , according to the numerical range of the terrain index corresponding to each sub-region, the target gradient of each sub-region is determined.

[0063] In some specific implementations, the area to be studied is the terrain of the central Yunnan urban agglomeration in the eastern and central regions of Yunnan Province, and its terrain potential index is between 0 and 1.22, which 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 potential index corresponding to the sub-region is in the above corresponding interval, it can be determined which target sub-interval corresponds to which target gradient the sub-region belongs to.

[0064] S20, analyzing the target sub-area from two evaluation dimensions: terrain gradient effect dimension and land gradient utilization characteristic dimension, and determining the land change degree assessment result of the land to be assessed based on the terrain gradient effect assessment results and land gradient utilization characteristic dimension assessment results of the multiple target sub-areas obtained.

[0065] In this embodiment, after the land to be evaluated is divided into a plurality of target sub-areas with different target gradients based on the terrain index, the target sub-areas are analyzed from two evaluation dimensions: the terrain gradient effect dimension and the land gradient utilization feature dimension.

[0066] The terrain gradient effect refers to the fact that the land type is significantly affected by the height of the soil, and the land type is obviously distributed in a stepped manner. Analyzing from the dimension of terrain gradient effect can analyze the temporal and spatial pattern change characteristics of the land area to be studied, thereby reasonably and effectively revealing the gradient distribution characteristics of land use affected by terrain.

[0067] Land gradient utilization characteristics refer to the dynamic characteristics of land gradient utilization changes in the land area to be studied. Land gradient utilization changes are the result of the combined effects of natural and socio-economic factors. There are significant differences in the driving factors and contribution intensity of different land use types. Analyzing land from the perspective of land gradient utilization characteristics can lay the foundation for subsequent land carbon emission effect analysis, thereby rationally regulating carbon emissions in the land area to be studied and predicting future land change trends.

[0068] In the technical solution provided in this embodiment, in order to accurately evaluate complex land areas, the land to be evaluated is first divided into a plurality of target sub-areas with different target gradients by using a terrain potential index calculated by using elevation values ​​and slope values; after evaluating each target sub-area in terms of terrain gradient effect and land gradient utilization characteristics, a comprehensive evaluation result of the degree of land change of the land to be evaluated is obtained, thereby achieving an accurate evaluation of complex land areas and providing an analytical basis for subsequent research and regulation of the carbon emission effects of complex land areas.

[0069] Second embodiment

[0070] In this embodiment, based on any embodiment, the land gradient utilization characteristic dimension includes the area change of the land use type, and in this embodiment, a land use transfer matrix is ​​used to quantify the area change of the land use type of the land to be evaluated.

[0071] The land use transfer matrix originates from the quantitative description of system states and state transitions 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 the study area at different periods, but also reflect the transfer-in and transfer-out areas of different land types at the beginning and end of the study. Therefore, the land use transfer matrix is ​​used in this implementation to analyze the area changes of land use types to be evaluated.

[0072] Specifically, the land use 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 use area of ​​each target sub-region, wherein the calculation expression of the land use transfer matrix is:

[0073]

[0074] 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.

[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 level II gradient, the transfer of land use types is mainly the transfer of grassland and forest land, and the main flow of grassland is to cultivated land and forest land, and the main flow of forest land is to cultivated land and grassland. With the growth of population, the demand for agricultural products such as grain and livestock continues to increase, and grassland and forest land are reclaimed as cultivated land to meet the survival needs of the population. The mutual transfer between forest land and grassland is not only the result of natural succession, but also affected by human activities such as deforestation and planting forage. At this gradient level, the outflow and inflow of cultivated land are relatively obvious, and the transfer-in and transfer-out amounts are basically the same. The transfer-in area of ​​urban land and industrial, mining and transportation construction land is much higher than the transfer-out area. This also shows that the urbanization expansion speed is fast at this gradient level, and the demand for land for urban construction, industry and transportation infrastructure construction is large.

[0082] In the level III gradient, the areas of cultivated land, forest land and grassland are obviously transferred out, and the other land types are mainly transferred in. Grassland, cultivated land and forest land are the top three land types in terms of transfer area, and the flow is mainly the mutual transfer between these three land types. Water areas, urban land, rural residential areas, industrial and mining and transportation construction land and unused land are land types with more transfer in than transfer out, and the overall area has increased. The water area of ​​the central Yunnan urban agglomeration as a whole has increased; the areas of urban land, rural residential areas, industrial and mining and transportation construction land have increased, and the increase in the areas of these four land types mainly comes from cultivated land, forest land and grassland. The area of ​​unused land has increased, mainly from cultivated land and grassland.

[0083] In the IV level gradient, forest land accounts for more than 50% of the area, and the areas of the other seven land use types have been greatly reduced. Under this gradient level, forest land, grassland and cultivated land are the three land use types with the most active area transfer. Forest land is mainly converted into grassland, followed by cultivated land. Grassland is mainly converted into forest land and cultivated land. Cultivated land is mainly transferred out to forest land and grassland. The areas of water areas, urban land, rural settlements, industrial and mining and transportation construction land and unused land have been greatly reduced, and the transfer intensity has weakened. The terrain in high-gradient areas is complex, and the steep mountains restrict the development and utilization of land, so the area of ​​land transfer naturally decreases.

[0084] In the V-level gradient, the transfer intensity of various land types decreased, and the transformation between different land types was more uniform than in other gradients. The transformation from forest land to other land types was the most obvious, with grassland and cultivated land as the main destinations. Grassland also showed a relatively obvious transfer behavior, with forest land as the main destination, followed by cultivated land. There were differences in the transfer behavior of cultivated land in different regions. The main land type transferred in was forest land, and the main land type transferred out was forest land and grassland. From the perspective of the transformation trajectory, the mutual transformation behavior between land types at this gradient level lacked vitality. The transfer-in and transfer-out areas of five land types, including water areas, urban land, rural settlements, industrial and mining and transportation construction land, and unused land, decreased, and the diversity of transformation types weakened.

[0085] Third embodiment

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

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

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

[0089]

[0090] 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;

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

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

[0093]

[0094] 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.

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

[0096] It should be noted that the rate of change of land use degree is usually studied by comparing the comprehensive land use degree index calculated in a more distant period with that calculated in a more recent period. Therefore, the time period corresponding to the first comprehensive land use degree index is later than the time period corresponding to the second comprehensive land use degree index.

[0097] For example, in a specific implementation, the value of the land gradient utilization degree classification index can be referred to as shown in the following Table 1.

[0098] Table 1. Gradient land use degree classification table

[0099] After obtaining the land use degree change rate, the land gradient utilization degree change trend in the land to be evaluated is analyzed based on the land use degree change rate of each target sub-area.

[0100] The following example is used as an analysis to illustrate the trend of land gradient utilization:

[0101] For example, 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 also 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).

[0102] Table 2. Gradient land use in the central Yunnan urban agglomeration from 2000 to 2020

[0103] Referring to Table 2, subtract the 2000 index from the comprehensive land use index in 2020 in Table 2 to obtain the changes in land development and utilization levels in the central Yunnan urban agglomeration in the past 20 years.

[0104] From 2000 to 2020, the overall land gradient utilization degree of the central Yunnan urban agglomeration showed a trend of continuous increase, indicating that the intensity of human activity interference and the degree of land development and utilization in the study area continued to increase. As the gradient level increases, the comprehensive index of land gradient utilization decreases, showing a trend from strong to weak, indicating that the degree of land development and utilization is obviously restricted by the terrain gradient, and land development in high-gradient areas is difficult. 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%, indicating that the land development degree of this gradient is high. In the process of urbanization, the development of the central Yunnan urban agglomeration has an increasing demand for land resources, which has promoted the increase in the degree of development and utilization of low-gradient land. The degree of land development and utilization of the II-level gradient has slowed down, and the maximum comprehensive index of land gradient utilization is 166.12. The change rate of land gradient utilization in the gradient interval of level I~II is positive, indicating that the corresponding area in this interval is in a period of sustained development from 2000 to 2020, with a large amount of land used for agriculture, industry and urban development, and the scale of land use has expanded, thereby increasing the degree of land development. In the gradient of level III~V, the comprehensive index of land gradient utilization shows a trend of fluctuation from decrease to increase to decrease. The change of land gradient utilization has experienced the stages of adjustment period, development period and adjustment period. From 2000 to 2005, the economic and social development of the central Yunnan urban agglomeration was relatively slow. Although the demand for land was large, the land development in high-gradient areas was difficult and costly, and the development was concentrated in relatively flat terrain areas; from 2005 to 2015, urbanization development accelerated, the demand for industrial and commercial land increased, and the development of the central Yunnan urban agglomeration began to "move towards the mountains and slopes" and build mountain towns.

[0105] The data in Table 1 are visualized and plotted as follows Figure 3 Shown is the spatial distribution map of changes in land gradient utilization in the central Yunnan urban agglomeration from 2000 to 2020.

[0106] It is easy to see from the chart that the degree of land development and utilization in the central Yunnan urban agglomeration has changed significantly. The degree of land use in most areas has increased, and the areas with a large increase in land gradient utilization mainly show clustered agglomeration characteristics, distributed in the eastern and southern regions; the areas with a small increase are scattered in the northern and western regions, and the overall spatial pattern of "high in the east and low in the west, high in the south and low in the north" is maintained, which is opposite to the topographic pattern of the central Yunnan urban agglomeration. Areas with lower altitudes and gentler slopes are the most developed areas; conversely, the degree of development is low. In terms of the magnitude of changes within the region, the areas with the largest changes in land gradient utilization are mainly distributed in the main urban area of ​​Kunming, Yuxi City, Qujing City, Luliang County, Shizong County and Luoping County, the central part of Chuxiong Prefecture and 7 counties and cities in Honghe Prefecture, with an increase in land gradient utilization of 11.28. The areas with large changes in land gradient utilization are mainly around the areas with the largest increase, forming a decreasing distribution of circles, and the increase in land gradient utilization is 5.57. The areas with medium-level changes in land gradient utilization are widely distributed, and the increase in land gradient utilization is 1.17. The areas with smaller changes in land gradient utilization are concentrated in the north, northwest, and southwest regions, and the change in land gradient utilization from 2000 to 2020 is 0.03. The areas with the smallest changes in land gradient utilization are staggered with areas with lower changes, and appear in the northern region with more complex topography. Such natural conditions have limited large-scale development and construction activities to a certain extent.

[0107] Fourth embodiment

[0108] In this embodiment, based on any embodiment, the land gradient utilization characteristic dimension includes the changes in the land gradient utilization structure, and in this embodiment, information entropy and / or balance index are used to quantify the changes in the land gradient utilization structure in the land to be evaluated.

[0109] Specifically, the information entropy of the target sub-region is calculated, and the balance index of the target sub-region is calculated according to the information entropy.

[0110] In this embodiment, information entropy is an important indicator that reflects the orderliness and diversity of regional land use structure. The higher the information entropy value, the lower the orderliness of the land use structure, the smaller the difference in area between different land types, and the more stable the land use structure. The calculation expression of information entropy is:

[0111]

[0112] If the area is in the undeveloped stage, the information entropy value is the smallest ( =0); if the region is mature and the land use types tend to be stable, the information entropy is the largest ( = ).

[0113] In this embodiment, the balance index can be used to reflect the comparability and homogeneity of land use of different land use types in different time periods. The calculation expression of the balance index is:

[0114]

[0115] 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.

[0116] The larger the balance index, the stronger the homogeneity of land gradient utilization in the central Yunnan urban agglomeration.

[0117] In this embodiment, after obtaining the land use change rate, the changes in the land gradient utilization structure in the land to be evaluated are analyzed based on the information entropy and / or balance index of each target sub-area. The changes in the land gradient utilization structure include the stability of the land use structure and the homogeneity of the land gradient utilization.

[0118] The following is an example to illustrate the analysis of the changes in land gradient utilization structure:

[0119] For example, 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 also 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).

[0120] Table 3. Land Gradient Utilization Structure Index of Central Yunnan Urban Agglomeration from 2000 to 2020

[0121] Referring to Table 3 above, the information entropy and balance index of land gradient utilization in the central Yunnan urban agglomeration showed an overall upward trend from 2000 to 2020, indicating that the land use structure in the study area has changed significantly, its orderliness is constantly increasing, and the land distribution is becoming more balanced. Further analysis found that the land use structure gradient of the central Yunnan urban agglomeration has been significantly different in the past 20 years. As the gradient level increases, the information entropy and balance index decrease, the area difference of each land use type at different gradient levels increases, the homogeneity of the land use structure weakens, and the stability of the land gradient utilization structure decreases. On the one hand, the information entropy and balance index of the level I gradient remained the highest during the study period, indicating that the land use types under this gradient level are balanced and diverse, and the areas of various types are relatively close. This also means that the land resources in this gradient are effectively utilized and managed, and the social, economic and environmental benefits of the land are high. Compared with other gradient levels, the information entropy and balance index of the level V gradient are the smallest, indicating that the scale of each type of land in this gradient varies greatly, showing that forest land occupies a dominant position, and the areas of other types of land use are relatively small. This also reveals the singleness and imbalance of land resource utilization in high-gradient areas, which may lead to regional ecological and environmental instability if it continues for a long time. On the other hand, there are differences in the change trends of information entropy and balance index of land use structure at different gradient levels from 2000 to 2020. During the study period, the information entropy and balance index of gradient levels I to III continued to grow, and the information entropy and balance index of gradient levels IV to V did not change before 2005, and then began to grow, but the increase was much smaller than that in 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 low-gradient areas is more balanced. Although land development in high-gradient areas is difficult, due to the reality of tight land use, the current status of land resource utilization and management in high-gradient areas has been improved, and the balance of land use structure is improving.

[0122] Fifth embodiment

[0123] In this embodiment, based on any one of the embodiments, the terrain gradient effect dimension includes at least one of an elevation value, a slope value, a terrain undulation and a distribution index.

[0124] Considering the profound impact of terrain factors on land use, four key terrain factors, namely elevation, slope, terrain undulation and distribution index, are selected in this embodiment to deeply analyze the terrain gradient effect of the land to be evaluated.

[0125] Elevation is an important indicator of regional topographic characteristics. Optionally, in some implementations, elevation is superimposed on land use to analyze the area change characteristics of different land types for every 100m increase in elevation;

[0126] Slope is an important representation of mountainous areas, representing the degree of inclination of surface units. Slope has a huge impact on agricultural production, social and economic development, and ecological environment. Optionally, in some embodiments, slope can be superimposed on land use to analyze the area change characteristics of each type of land for every 1° increase in slope.

[0127] The terrain relief can directly reflect the characteristics of regional terrain relief and is a quantitative indicator for describing landform morphology and classifying landform types. Optionally, in some embodiments, the terrain relief can be superimposed on land use to further analyze the area change characteristics of each land type when the terrain relief increases by 50m.

[0128] The distribution index is mostly used to describe the distribution of different land use types in the study area on different terrain gradients. It can effectively eliminate the impact of differences in terrain sections and land use areas, and indicate the distribution advantages of different land types. Optionally, in some embodiments, the distribution index is combined with the terrain position index to conduct a comprehensive analysis of the distribution of land use types on different terrain gradients.

[0129] In addition, as an implementation solution, Figure 4 This is a schematic diagram of the architecture of the hardware operating environment of the computer system involved in the embodiment of the present application.

[0130] like Figure 4 As 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), an input unit such as a keyboard (Keyboard), and the optional user interface 1003 may also 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 also be a storage device independent of the aforementioned processor 1001.

[0131] Those skilled in the art will understand that Figure 4 The computer system architecture shown in the figure does not constitute a limitation of the computer system, and may include more or less components than shown in the figure, or combine certain components, or arrange the components differently.

[0132] like Figure 4As shown, 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 assessment program based on gradient division and dual-dimensional analysis. Among them, the operating system is a program that manages and controls the hardware and software resources of the computer system, the land change degree assessment program based on gradient division and dual-dimensional analysis, and the operation of other software or programs.

[0133] exist Figure 4 In the computer system shown, the user interface 1003 is mainly used to connect to the terminal and communicate data with the terminal; the network interface 1004 is mainly used for the background server and communicates data with the background server; the processor 1001 can be used to call the land change degree assessment program based on gradient division and two-dimensional analysis stored in the memory 1005.

[0134] In this embodiment, the computer system includes: a memory 1005, a processor 1001, and a land change degree assessment program based on gradient division and dual-dimensional analysis stored in the memory and executable on the processor, wherein:

[0135] When the processor 1001 calls the land change degree assessment program based on gradient division and dual-dimensional analysis stored in the memory 1005, the following operations are performed:

[0136] 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;

[0137] The target sub-area is analyzed from two evaluation dimensions: terrain gradient effect dimension and land gradient utilization characteristic dimension, and based on the terrain gradient effect evaluation results and land gradient utilization characteristic dimension evaluation results of multiple target sub-areas obtained, the land change degree evaluation results of the land to be evaluated are determined.

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

[0139] Taking the target radius range as a unit, dividing the land to be assessed into a plurality of sub-areas;

[0140] Calculating the terrain index corresponding to each of the sub-areas;

[0141] Determining the target gradient of each sub-region according to the numerical range of the terrain index corresponding to each sub-region;

[0142] The sub-regions in the same target gradient are determined as the target sub-region composed of one or more sub-regions.

[0143] When the processor 1001 calls the land change degree assessment program based on gradient division and dual-dimensional analysis stored in the memory 1005, the following operations are performed:

[0144] 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;

[0145] 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:

[0146]

[0147] 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.

[0148] When the processor 1001 calls the land change degree assessment program based on gradient division and dual-dimensional analysis stored in the memory 1005, the following operations are performed:

[0149] 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;

[0150] When the processor 1001 calls the land change degree assessment program based on gradient division and dual-dimensional analysis stored in the memory 1005, the following operations are performed:

[0151] 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;

[0152] When the processor 1001 calls the land change degree assessment program based on gradient division and dual-dimensional analysis stored in the memory 1005, the following operations are performed:

[0153] 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.

[0154] In addition, it can be understood by those skilled in the art that all or part of the processes in the method for implementing the above embodiment can be completed by instructing the relevant hardware through a computer program. The computer program includes program instructions, and the computer program can be stored in a storage medium, which is a computer-readable storage medium. The program instructions are executed by at least one processor in a computer system to implement the process steps of the embodiment of the above method.

[0155] Therefore, the present application also provides a computer-readable storage medium, which stores a land change degree assessment program based on gradient partitioning and two-dimensional analysis. When the land change degree assessment program based on gradient partitioning and two-dimensional analysis is executed by a processor, it implements the various steps of the land change degree assessment method based on gradient partitioning and two-dimensional analysis described in the above embodiment.

[0156] The computer-readable storage medium may be a USB flash drive, a mobile hard disk, a read-only memory (ROM), a magnetic disk, or an optical disk, etc., which are computer-readable storage media that can store program codes.

[0157] It should be noted that since the storage medium provided in the embodiment of the present application is the storage medium used to implement the method of the embodiment of the present application, based on the method introduced in the embodiment of the present application, the person skilled in the art can understand the specific structure and deformation of the storage medium, so it is not repeated here. All storage media used in the method of the embodiment of the present application belong to the scope of protection of this application.

[0158] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware. Moreover, the present application may take 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.

[0159] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems) and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0160] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0161] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0162] It should be noted that in the claims, any reference signs placed between brackets shall not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claim. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The present application may be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third etc. does not indicate any order. These words may be interpreted as names.

[0163] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0164] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

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; The target sub-area is analyzed from two evaluation dimensions: terrain gradient effect dimension and land gradient utilization characteristic dimension, and based on the terrain gradient effect evaluation results and land gradient utilization characteristic dimension evaluation results of multiple target sub-areas obtained, the land change degree evaluation results of the land to be evaluated are determined.

2. The land change degree assessment method based on gradient division and two-dimensional analysis according to claim 1, characterized in that: 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.

3. The land change degree assessment method based on gradient division and two-dimensional analysis according to claim 1 or 2, 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.

4. 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.

5. The land change degree assessment method based on gradient division and two-dimensional analysis according to claim 4 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.

6. The land change degree assessment method based on gradient division and two-dimensional analysis according to claim 4, 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.

7. The land change degree assessment method based on gradient division and two-dimensional analysis according to claim 4, 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.

8. 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.

9. 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 8 are implemented.

10. 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 8.

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