Method and system for merging continuous scales of planar natural elements based on morphing

Abstract

The present application relates to the technical field of cartographic generalization, and particularly relates to a continuous scale merging method and system for areal natural features based on Morphing, which establishes a continuous scale expression concept model, that is, inputting large scale features and small scale features, outputting intermediate scale features according to the change of transformation degree, obtaining the corresponding relationship of large scale and small scale map features according to the area overlay rate, merging a group of large scale features corresponding to the same small scale feature by using the Greiner-Hormann algorithm after obtaining the corresponding relationship of features, classifying and simplifying the boundary lines of the merged features, combining the simplified boundary lines according to the order of the original feature boundary lines, and obtaining the final intermediate scale features. The present application realizes the continuous scale merging and boundary simplification operation of mutually separated areal natural features.

Description

Technical Field

[0001] This invention relates to the field of cartographic generalization technology, and in particular to a method and system for merging continuous scales of planar natural elements based on morphing. Background Technology

[0002] Existing technologies cannot merge separate areal natural features (such as lakes and islands) under continuous scale conditions. Current areal feature merging methods mainly include one-time merging and progressive merging. One-time merging cannot output data at multiple scales; if the target scale value is changed to achieve the effect of outputting data at multiple scales, the intermediate merging results are prone to inconsistencies. Progressive merging refers to merging step by step. Although it can inherit the results of the previous step to obtain a coherent intermediate scale representation, this method still has two problems: first, it relies on only one scale data to generate the result, which is blind and can easily lead to an unsatisfactory final merging result; second, progressive merging focuses more on phased processing, requiring evaluation and rectification after each step of the generalization operation. Its essence is still based on discrete steps and cannot achieve true continuous scale cartographic generalization.

[0003] Currently, methods for merging continuous scale features only apply to adjacent isometric natural features. These methods only select and calculate the features to be merged, without considering how the merging process works or how the boundaries of the merged features are simplified. However, cartographic generalization involves both the selection of features to be merged and boundary simplification. Summary of the Invention

[0004] This invention aims to solve the problem that existing algorithms cannot merge continuous scales, which affects the continuous scale representation of planar natural elements. It proposes a continuous scale merging method and system for planar natural elements based on Morphing. It utilizes the Greiner-Hormann algorithm and the Morphing concept in computer graphics to perform continuous scale merging and boundary simplification operations on mutually separated planar natural elements.

[0005] To achieve the above objectives, the technical solution adopted is:

[0006] This invention provides a method for continuous scale merging of planar natural features based on morphing, comprising:

[0007] Establish a conceptual model for continuous scale representation, that is, input large-scale and small-scale elements, and output intermediate-scale elements according to the changes in the degree of transformation;

[0008] Obtain the correspondence between large-scale and small-scale map elements based on the area overlay ratio;

[0009] After obtaining the correspondence between elements, a group of large-scale elements that correspond to the same small-scale element are merged using the Greiner-Hormann algorithm.

[0010] The boundary lines of the merged elements are classified and simplified.

[0011] The simplified boundary lines are combined in the order of the original feature boundary lines to obtain the final intermediate scale features.

[0012] According to the continuous scale merging method for planar natural elements based on morphing of the present invention, for planar elements that exhibit corresponding relationships at different scales, let the large scale T be... a The lower surface element is a, and the small scale is T. b The lower face element is b, and the middle scale is T. Mud If the polygon feature below is Mid, then the continuous scale merging problem is transformed into a shape interpolation problem between polygon features a and b, outputting any merged state between a and b; therefore, the conceptual model expression is:

[0013] Mid = f(a, b, t)

[0014]

[0015] Where f is the shape expression function, t is the degree of transformation, and is related to T Mid It is monotonically continuous, t∈[0,1]. When t=0, Mid is a, and when t=1, Mid is b.

[0016] According to the continuous scale merging method for areal natural features based on morphing of the present invention, further, obtaining the correspondence between large-scale and small-scale map features based on the area overlay rate includes:

[0017] If the ratio of the area of ​​the overlapping part to the area of ​​the larger scale element is greater than a threshold when two scale elements are overlaid, then the two scale elements are considered to be in a corresponding relationship.

[0018] According to the continuous scale merging method of planar natural elements based on Morphing of the present invention, the merging is further performed using the Greiner-Hormann algorithm, which includes a marking stage and a tracking stage. The marking stage is used to obtain the chain of coordinate points that are close to each other on the edge of the polygon, and the tracking stage is used to obtain the coordinate sequence of the outer contour of the merged polygon and the coordinate sequence of the newly generated island.

[0019] According to the continuous scale merging method for planar natural elements based on Morphing of the present invention, the marking stage further includes:

[0020] Determine the directions of the two polygons to be merged. If the directions are opposite, reverse the direction of one of the polygon's edges. If the directions are the same, do nothing. The direction of the polygon is calculated using the vertex vector formula.

[0021] Iterate through the coordinates of points on the edges of the two polygons, compare the distances between the points, obtain the coordinates of the point where the maximum distance between the two polygons is located, and use this point as the starting coordinate point of the merged polygon.

[0022] Traverse the coordinate sequence of the two polygon edges and mark the edges whose distance is less than a distance threshold R. d Based on the marked coordinates, establish the connection between point chains; according to the order of the point chains, the first point of the point chain is recorded as the exit point, and the last point of the point chain is recorded as the entry point;

[0023] Based on the relationship between the point chains in the two polygon coordinate sequences, and following the out-in point principle, establish the connection between the out-in points of the two elements.

[0024] According to the continuous scale merging method for planar natural features based on Morphing of the present invention, the distance threshold R is further... d The calculation formula is as follows:

[0025] R d =α×(L visual +ω)×T mid

[0026] Where α represents the adjustment coefficient, L visual T represents the minimum resolvable distance of the human eye, ω represents the width of the edge, and T represents the minimum resolvable distance of the human eye. Mid Indicates an intermediate scale.

[0027] According to the continuous scale merging method for planar natural elements based on Morphing of the present invention, the tracking stage further includes:

[0028] For obtaining the outer contour coordinate sequence, starting from the starting coordinate point obtained in the marking stage, the feature coordinate sequence is traversed. When the coordinate point marked as the exit point is encountered for the first time, it is turned to the entry point associated with another feature. Then, starting from the current entry point of that feature, it is moved along its coordinate sequence direction. When the exit point is encountered, it is turned back to the entry point associated with the original feature and continues to move along the coordinate sequence until it returns to the starting point. The coordinates of the points along the way are connected to generate the outer contour of the merged polygon.

[0029] To obtain the coordinate sequence of an island, first traverse the feature coordinate sequence. When the first coordinate point marked as the entry point is encountered, the coordinates are recorded. Then, continue along the feature coordinate sequence until the coordinate point marked as the exit point is reached. Then, switch to the entry point of another associated feature, follow the coordinate sequence to reach the next exit point, and return to the starting point through the association relationship to generate the coordinate sequence of an island.

[0030] According to the continuous scale merging method for planar natural elements based on Morphing of the present invention, the boundary lines of the merged elements are further classified and simplified, including the Morphing transformation method used on the boundary lines corresponding to small-scale elements: first, the intersection points and the first and last points of the two corresponding lines are taken; then, the intersection points, the first and last points, and the points on the line segments of the two corresponding lines are matched pairwise; let the points of the boundary lines of the merged elements be v. i The point corresponding to the line on a small-scale feature is v. j After simplification, the point on the boundary line is v. h Then v h The formula for calculating the degree of transformation t is as follows:

[0031] v h =t×v i +(1-t)×v j .

[0032] According to the continuous scale merging method for planar natural elements based on Morphing of the present invention, the classification and simplification of the boundary lines of the merged elements further includes using a ternary curvature group-based division method for boundary lines that do not correspond to small-scale elements:

[0033] First, identify the bends on the non-corresponding lines of the merged elements based on the bend direction of adjacent line segments, and use the line connecting the beginning and end points of the bend as the baseline.

[0034] Then, when the distance from all points on the curve to the midpoint of the baseline is less than the distance threshold R... d Mark the bend at that time;

[0035] Finally, following the order of the uncorresponding lines, traverse the bends. When a single bend marked for simplification appears, replace the bend with the baseline. When two consecutive marked bends appear, replace the bend with the baseline of the one with the smaller area. When three consecutive marked bends appear, if the area of ​​the middle bend is less than the sum of the areas of the two adjacent bends, replace the two adjacent bends with the baseline. In other cases, replace the middle bend with the baseline.

[0036] Furthermore, the present invention also provides a continuous scale merging system for planar natural features based on morphing, comprising:

[0037] The conceptual model building module is used to build a continuous scale conceptual model, that is, inputting large-scale and small-scale elements, and outputting intermediate-scale elements according to the change of the degree of transformation.

[0038] The correspondence acquisition module is used to obtain the correspondence between large-scale and small-scale map elements based on the area overlay rate;

[0039] The feature merging module is used to merge a group of large-scale features that correspond to the same small-scale feature after obtaining the feature correspondence.

[0040] The boundary simplification module is used to classify and simplify the boundary lines of merged elements.

[0041] The combination module is used to combine the simplified boundary lines according to the order of the original feature boundary lines to obtain the final intermediate scale features.

[0042] The beneficial effects achieved by adopting the above technical solution are:

[0043] This invention enables the merging of planar natural elements under continuous scale conditions. By inputting small-scale and large-scale graphics, it can output arbitrary intermediate scale data based on the degree of transformation t, i.e., the intermediate scale value. This continuous merging capability solves the technical problem of continuous expression of planar natural elements.

[0044] This invention constrains the objects to be merged based on the correspondence between the elements of two scales, merges them according to the distance, and simplifies the boundary classification of the merged elements to avoid self-intersection when expressing them continuously, while maintaining the basic shape characteristics of the elements, thus meeting the scientific requirements for continuous expression of geospatial data. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. The drawings are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the present invention to all embodiments.

[0046] Figure 1 This is a flowchart of a method for merging continuous scales of planar natural elements based on Morphing, according to an embodiment of the present invention.

[0047] Figure 2 This is a schematic diagram illustrating the acquisition of map element correspondences according to an embodiment of the present invention;

[0048] Figure 3 This is a schematic diagram of the merging of planar natural elements according to an embodiment of the present invention;

[0049] Figure 4This is a schematic diagram of obtaining the corresponding line according to an embodiment of the present invention;

[0050] Figure 5 This is a schematic diagram illustrating the simplification of corresponding lines using the Morphing method in an embodiment of the present invention;

[0051] Figure 6 This is a schematic diagram illustrating the simplification of uncorresponding lines using a ternary bending group division method according to an embodiment of the present invention.

[0052] Figure 7 This is a schematic diagram of the interpolation graph according to an embodiment of the present invention;

[0053] Figure 8 These are the merging and simplification results under different transformation degrees t in the embodiments of the present invention. Detailed Implementation

[0054] The exemplary solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art.

[0055] like Figure 1 As shown, this embodiment discloses a method for merging continuous scales of separate planar natural features, based on Morphing, including the following steps:

[0056] Step S101: Establish a continuous scale representation concept model, that is, input large-scale elements and small-scale elements, and output intermediate scale elements according to the change of the degree of transformation.

[0057] For surface features that exhibit corresponding relationships at different scales, let the large scale be T. a The lower surface element is a, and the small scale is T. b The lower face element is b, and the middle scale is T. Mid The face feature below is called Mid. 'a' has a more detailed representation than 'b', and the level of detail in Mid falls between that of 'a' and 'b'. Therefore, the continuous scale merging problem is transformed into a shape interpolation problem between face features 'a' and 'b', which can output any merged state between 'a' and 'b'. The conceptual model expression is then:

[0058] Mid = f(a, b, t)

[0059]

[0060] Where f is the shape expression function established in this scheme, t is the degree of transformation, and T is related to the shape expression function. MidIt is monotonically continuous, t∈[0,1]. When t=0, Mid is a, and when t=1, Mid is b.

[0061] Step S102: Obtain the correspondence between large-scale and small-scale map elements based on the area overlay rate, and use this as a constraint condition for merging intermediate-scale elements.

[0062] The correspondence between large-scale and small-scale map features represents the merging relationship between features, which this scheme will obtain based on the area overlay ratio. By overlaying and analyzing the features at two scales, if the ratio of the overlapping area to the area of ​​the large-scale feature itself is greater than a threshold, then the two scale features are considered to have a correspondence. For example... Figure 2 Almost all large-scale features are included within small-scale feature b1, and therefore all correspond to b1.

[0063] Step S103: To gradually transform large-scale features into small-scale features, after obtaining the feature correspondence, it is necessary to merge a group of large-scale features corresponding to the same small-scale feature using the Greiner-Hormann algorithm according to the degree of transformation t. For example... Figure 2 All large-scale features are objects that can be merged with each other. The Greiner-Hormann algorithm used for merging includes a marking phase and a tracking phase.

[0064] The purpose of the marking phase is to obtain chains of coordinate points that are close together on the edge of the polygon (a chain of consecutive marked points in a coordinate sequence is called a point chain), specifically including:

[0065] ① Polygon preprocessing. Determine the directions of the two polygons to be merged. If their directions are opposite, reverse the direction of one of the polygon's edges. If their directions are the same, do nothing. The polygon directions can be calculated using the vertex vector formula, as follows:

[0066] K=(x2-x1)×(y3-y2)-(x3-x2)×(y2-y1)

[0067] In the formula, B(x2,y2) is any convex vertex of the polygon, A(x1,y1) is the predecessor vertex of B, and C(x3,y3) is the successor vertex of B. If K>0, the polygon direction is counterclockwise; otherwise, if K<0, the polygon direction is clockwise. Traverse the coordinates of points on the edges of the two polygons, compare the distances between the points, obtain the coordinates of the point where the maximum distance between the two polygons is found, and use this point as the starting coordinate point of the new polygon (the merged polygon). Figure 3 (At the pentagram).

[0068] ② Obtain the in and out points of the chain of nearest neighbor coordinate points. Traverse the coordinate sequences of the two polygon edges, marking the points on the two edges whose distance is less than a distance threshold R. d The point, distance to threshold R d Also about T Mid Monotonically continuous, corresponding to the value of t, is calculated as follows:

[0069] R d =α×(L visual +ω)×T mid

[0070] Where Δ represents the adjustment coefficient, L visual ω represents the minimum resolvable distance of the human eye, and ω represents the width of the edge. Based on the marked coordinates, establish relationships between point chains. Following the order of the point chains, the first point of each chain is designated as the exit point, and the last point as the entry point; if a point chain contains only one coordinate point, the mark for that coordinate point is deleted. For example... Figure 3 As shown, the triangle is marked as the exit point, the rectangle is marked as the entry point, and the remaining points are marked points on the point chain.

[0071] ③ Establish the relationship between the entry and exit points of the two elements. Based on the relationship between the point chains in the coordinate sequences of the two polygons, and following the "entry-exit point" principle, determine the distance threshold R. d Establish the in-point and out-point connections between two elements. For one-to-many relationships in a point chain, in... Figure 3 In (b), if two point chains α and β of one element correspond to one point chain γ of another element, then the point coordinates between the two point chains α and β are marked, so that they are merged into one point chain, and then the relationship between the out point and the in point is established.

[0072] The tracking phase aims to obtain the coordinate sequence of the outer contour of the merged polygon and the coordinate sequence of the newly generated "island," specifically including:

[0073] ① Establish the outer contour of the merged polygon. Starting from the initial coordinate point obtained in the marking stage, record the coordinates and traverse the feature coordinate sequence. When the first coordinate point marked as an exit point is encountered, move to the associated entry point on another feature. Then, starting from the current entry point of that feature, proceed along its coordinate sequence. When an exit point is encountered, return to the associated entry point on the original feature and continue moving along the coordinate sequence until returning to the starting point. The coordinates of the points along the way are concatenated to generate the outer contour of the merged polygon, as shown below. Figure 3 (d)

[0074] ② Obtaining the coordinate sequence of newly generated "islands". Since "islands" are openings within features, their coordinate sequences differ from those of the outer contour. Therefore, the feature coordinate sequence is first traversed. Coordinates are only recorded when a point marked as an inlet is encountered for the first time. The process continues along the feature coordinate sequence until an outlet point is reached, at which point the system moves to the inlet point of another associated feature. The system then follows the coordinate sequence to the next outlet point, returning to the starting point of the recording process through the association. Recording ends, and the coordinate sequence of the first newly generated "island" is generated. By tracking the remaining inlet points in the feature coordinate sequence, the coordinate sequences of all newly generated "islands" can be obtained sequentially, excluding those with areas smaller than the minimum area (where the area is a distance threshold R). d The squared "island" has the following merging effect: Figure 3 As shown in (e).

[0075] Step S104: In order to make the boundary change smooth, the boundary lines of the merged elements are classified and simplified.

[0076] After merging elements, boundary simplification is required. To achieve a smooth transition from large-scale to small-scale graphics, boundaries need to be categorized: firstly, boundary lines that correspond to the small-scale graphics, i.e., establishing buffer zones for elements. Figure 4 (Medium-dark blue graphic), the small-scale feature boundary line within the buffer zone is trimmed to form the corresponding line ( Figure 4 (Medium-dark purple line), and based on this corresponding line, extract the point chain of the merged feature boundary ( Figure 4 The black line in the middle; secondly, the remaining boundary lines among the elements that do not correspond to small-scale elements (the black line in the middle); Figure 4 (Medium gray line).

[0077] The simplification between corresponding lines uses the Morphing method, as detailed below:

[0078] ① Feature point acquisition. Take the intersection point and the first and last points of two corresponding lines. Figure 5 (Points of the middle triangle). If there are no intersecting points, only the first and last points are considered.

[0079] ② Feature point matching. Match the intersecting points and the beginning and end points of the two corresponding lines pairwise. Divide the line into segments at the feature points, and match the segments. The remaining unmatched points are matched to points on another line segment with the same length ratio as their respective segments. Figure 5 (a1 and b1, a2 and b2 correspond to each other).

[0080] ③ Interpolation transformation. Let v be the point on the boundary line of the merged elements. i The point corresponding to the line on a small-scale feature is v. j The point of the interpolation line, i.e., the simplified boundary line, is v. h Then v hThe formula for calculating the degree of transformation t is as follows:

[0081] v h =t×v i +(1-t)×v j .

[0082] For boundary lines in the merged feature boundaries that do not correspond to small-scale features, a ternary curvature group-based partitioning method will be used for simplification, as follows:

[0083] ① Bending Recognition. Traverse each segment on the line sequentially, determining the bending direction between the current segment and the next. A change in bending direction indicates the end of a bend and the beginning of a new one. The line connecting the beginning and end points of the bend forms the baseline. For example, Figure 6 The surfaces are represented by different colors.

[0084] ② Curvature simplification judgment. When the distance from all points in the curve to the midpoint of the baseline is less than the distance threshold R. d At that time, mark the bend, such as Figure 6 The curves are a1, a2, a3, and a4.

[0085] ③ Simplify the three-dimensional bend group. Traverse the bends in the order of uncorresponding lines. When a single bend marked for simplification appears, replace that bend with the baseline. Figure 6 (Region A). When two consecutive marked bends appear, the bend with the smaller area is replaced by its baseline. When three consecutive marked bends appear, if the area of ​​the middle bend is less than the sum of the areas of the two adjacent bends, the two adjacent bends are replaced by the baseline; otherwise, the middle bend is replaced by the baseline (e.g., ...). Figure 6 (Region B). After continuously marked bends are simplified, add subsequent coordinate points directly, and repeat steps ①-③ until all bends are simplified.

[0086] Step S105: Generation of interpolated graphs.

[0087] The results of simplifying and transforming corresponding and non-corresponding lines are combined according to the order of the original feature boundary lines to obtain the final interpolated graph (e.g., Figure 7 (As shown). Figure 8 for Figure 2 The merging and simplification results of map elements under different t values ​​show that the resulting changes are smooth, continuous, and scientifically reasonable.

[0088] Corresponding to the above method, this embodiment also proposes a continuous scale merging system for planar natural elements based on morphing, including:

[0089] The conceptual model building module is used to establish a continuous scale representation conceptual model, that is, inputting large-scale and small-scale elements, and outputting intermediate-scale elements according to the changes in the degree of transformation.

[0090] The correspondence acquisition module is used to obtain the correspondence between large-scale and small-scale map elements based on the area overlay rate.

[0091] The feature merging module is used to merge a group of large-scale features that correspond to the same small-scale feature after obtaining the feature correspondence. The Greiner-Hormann algorithm is used for this purpose.

[0092] The boundary simplification module is used to classify and simplify the boundary lines of merged elements.

[0093] The combination module is used to combine the simplified boundary lines according to the order of the original feature boundary lines to obtain the final intermediate scale features.

[0094] Unless otherwise specifically stated, the components, steps, numerical expressions, and values ​​described in these embodiments do not limit the scope of the invention.

[0095] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0096] The units and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations are not considered to be beyond the scope of this invention.

[0097] Those skilled in the art will understand that all or part of the steps in the above methods can be implemented by a program instructing related hardware, and the program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk. Optionally, all or part of the steps in the above embodiments can also be implemented using one or more integrated circuits. Accordingly, each module / unit in the above embodiments can be implemented in hardware or as a software functional module. This invention is not limited to any particular combination of hardware and software.

[0098] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features within the technical scope disclosed in the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for continuous scale merging of planar natural elements based on Morphing, characterized in that, include: Step 1: Establish a continuous scale representation concept model, that is, input large-scale elements and small-scale elements, and output intermediate scale elements according to the change of the degree of transformation. Step 2: Obtain the correspondence between large-scale and small-scale map elements based on the area overlay ratio; Step 3: After obtaining the correspondence between features, a group of large-scale features corresponding to the same small-scale feature are merged using the Greiner-Hormann algorithm, including the marking phase and the tracking phase: The marking phase specifically includes: Determine the directions of the two polygons to be merged. If the directions are opposite, reverse the direction of one of the polygon's edges. If the directions are the same, do nothing. The direction of the polygon is calculated using the vertex vector formula. Iterate through the coordinates of points on the edges of the two polygons, compare the distances between the points, obtain the coordinates of the point where the maximum distance between the two polygons is located, and use the coordinates of the point where the maximum distance between the two polygons is located as the starting coordinate point of the merged polygon. Traverse the coordinate sequence of the two polygon edges and mark the edges whose distance is less than a distance threshold R. d Based on the marked coordinates, establish the connection between point chains; according to the order of the point chains, the first point of the point chain is recorded as the exit point, and the last point of the point chain is recorded as the entry point; Based on the relationship between the point chains in the two polygon coordinate sequences, and following the out-in point principle, establish the connection between the out-in points of the two elements. The tracking phase specifically includes: For obtaining the outer contour coordinate sequence, starting from the starting coordinate point obtained in the marking stage, the feature coordinate sequence is traversed. When the coordinate point marked as the exit point is encountered for the first time, it is turned to the entry point associated with another feature. Then, starting from the current entry point of that feature, it is moved along its coordinate sequence direction. When the exit point is encountered, it is turned back to the entry point associated with the original feature and continues to move along the coordinate sequence until it returns to the starting point. The coordinates of the points along the way are connected to generate the outer contour of the merged polygon. To obtain the coordinate sequence of an island, first traverse the feature coordinate sequence. When the first coordinate point marked as the entry point is encountered, the coordinates are recorded. Then, continue along the feature coordinate sequence to the coordinate point marked as the exit point, then turn to the entry point of another associated feature, follow the coordinate sequence to reach the next exit point, and return to the starting point through the association relationship to generate the coordinate sequence of an island. Step 4: Classify and simplify the boundary lines of the merged elements, including using the Morphing transformation method for the boundary lines corresponding to small-scale elements. Step 5: Combine the simplified boundary lines according to the order of the original feature boundary lines to obtain the final intermediate scale features.

2. The method for continuous scale merging of planar natural elements based on Morphing according to claim 1, characterized in that, For surface features that exhibit corresponding relationships at different scales, let the large scale be T. a The lower surface element is a, and the small scale is T. b The lower face element is b, and the middle scale is T. Mid If the polygon feature below is Mid, then the continuous scale merging problem is transformed into a shape interpolation problem between polygon features a and b, outputting any merged state between a and b; therefore, the conceptual model expression is: Mid = f(a, b, t) Where f is the shape expression function, t is the degree of transformation, and is related to T Mid It is monotonically continuous, t∈[0,1]. When t=0, Mid is a, and when t=1, Mid is b.

3. The method for continuous scale merging of planar natural elements based on Morphing according to claim 1, characterized in that, Obtaining the correspondence between large-scale and small-scale map features based on area overlay ratio includes: If the ratio of the area of ​​the overlapping part to the area of ​​the larger scale element is greater than a threshold when two scale elements are overlaid, then the two scale elements are considered to be in a corresponding relationship.

4. The method for continuous scale merging of planar natural elements based on Morphing according to claim 1, characterized in that, The marking phase is used to obtain the chain of coordinate points that are close to each other on the edge of the polygon, and the tracking phase is used to obtain the coordinate sequence of the outer contour of the merged polygon and the coordinate sequence of the newly generated island.

5. The method for continuous scale merging of planar natural elements based on Morphing according to claim 1, characterized in that, Distance threshold R d The calculation formula is as follows: R d =α×(L visual +ω)×T mid Where α represents the adjustment coefficient, L visual T represents the minimum resolvable distance of the human eye, ω represents the width of the edge, and T represents the minimum resolvable distance of the human eye. Mid Indicates an intermediate scale.

6. The method for continuous scale merging of planar natural elements based on Morphing according to claim 2, characterized in that, The Morphing transformation method specifically includes: first, identifying the intersection points and the first and last points of two corresponding lines; then, matching the intersection points, first and last points, and points on the line segments of the two corresponding lines pairwise; and finally, denoting the points on the boundary lines of the merged elements as v. i The point corresponding to the line on a small-scale feature is v. j After simplification, the point on the boundary line is v. h Then v h The formula for calculating the degree of transformation t is as follows: v h =t×v i +(1-t)×v j 。 7. The method for continuous scale merging of planar natural elements based on Morphing according to claim 6, characterized in that, The classification and simplification of the boundary lines of the merged elements also includes using a ternary curvature group-based partitioning method for boundary lines that do not correspond to small-scale elements: First, identify the bends on the non-corresponding lines of the merged elements based on the bend direction of adjacent line segments, and use the line connecting the beginning and end points of the bend as the baseline. Then, when the distance from all points on the curve to the midpoint of the baseline is less than the distance threshold R... d Mark the bend at that time; Finally, traverse the bends in the order of the uncorresponding lines. When a single bend that has been simplified is found, replace that bend with the baseline. When two consecutive marked bends appear, the bend with the smaller area is replaced with its baseline; When three consecutive marked bends appear, if the area of ​​the middle bend is less than the sum of the areas of the two adjacent bends, then the two adjacent bends are replaced with the baseline; otherwise, the middle bend is replaced with the baseline.

8. A continuous scale merging system for planar natural elements based on morphing, characterized in that, A method for implementing continuous scale merging of planar natural features based on Morphing as described in claim 1 includes: The conceptual model building module is used to build a continuous scale conceptual model, that is, inputting large-scale and small-scale elements, and outputting intermediate-scale elements according to the change of the degree of transformation. The correspondence acquisition module is used to obtain the correspondence between large-scale and small-scale map elements based on the area overlay rate; The feature merging module is used to merge a group of large-scale features that correspond to the same small-scale feature after obtaining the feature correspondence. The boundary simplification module is used to classify and simplify the boundary lines of merged elements. The combination module is used to combine the simplified boundary lines according to the order of the original feature boundary lines to obtain the final intermediate scale features.

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