CN116448061B - Fixed equal-altitude detection method, system and device for topographic map - Google Patents
Fixed equal-altitude detection method, system and device for topographic map Download PDFInfo
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- G—PHYSICS
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- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C5/00—Measuring height; Measuring distances transverse to line of sight; Levelling between separated points; Surveyors' levels
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
- G01B21/16—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring distance of clearance between spaced objects
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Abstract
The application provides a method, a system and a device for detecting a fixed equal-altitude of a topographic map, which belong to the technical field of mapping geographic information data processing, and the method comprises the following steps: opening a topographic map of a basic scale of the dxf format to be detected; acquiring coordinate information and elevation values of each contour line in a topographic map, combining the coordinate information and the elevation values to generate detection information of each contour line, and adding the detection information of each contour line into a linked list; grouping detection information of the contour lines in the linked list according to the areas described by the coordinate information of the contour lines; calculating the contour distance of each group according to the elevation value of each contour line; a fixed contour of the topography is determined based on the contour of each group. The application can accurately identify all contour lines and corresponding elevation values in the dxf format basic scale topographic map, judge whether a fixed contour distance exists or not after summarizing, and effectively improve the detection efficiency of topographic map data.
Description
Technical Field
The application relates to the technical field of mapping geographic information data processing, in particular to a method, a system and a device for detecting a fixed constant-altitude of a topographic map.
Background
For the basic scale topography data in dxf format, a large number of contours are contained. The contour lines are indispensable element data in the topographic map, and can very vividly show the topographic features. According to relevant standard, the contour distance between two adjacent contour lines in the topographic map of the scale is specified as a specific value and must be identical.
The contour line has extremely important significance for fields such as civilian life, scientific research and the like. After the contour line data precision accords with a certain standard, the secret-related standard is achieved. According to the relevant specifications: comprising contour lines with a contour distance of better than 20 meters (inclusive), the secret level is a secret level.
In units and departments that produce, transmit, use and store sensitive contour data, it is necessary to identify the security level of the contour data, and manage the data according to the security requirement of the corresponding level, so as to prevent the occurrence of a security leakage event of the sensitive data.
Currently, security level detection is performed on the contour lines in the dxf format, and attribute information of a topographic map is detected mainly manually. Or opening dxf file by Auto CAD, finding different contour lines in the graph, checking elevation values of the contour lines through LIST command, and judging the contour distance manually.
However, the manual discrimination method relies on the third party software, which not only complicates the operation, but also makes errors and causes security erroneous determination for the topographic map including a large number of contour lines. And the batch processing cannot be performed in this way, and the execution efficiency is low. If the high-security contour is judged to be low-security, the risk of disclosure of sensitive data can be caused; if a low-security contour is determined to be high-security, reasonable use of the data may be affected.
Disclosure of Invention
Aiming at the problems existing in the prior art, the application aims to provide a method, a system and a device for detecting the fixed equal-altitude of a topographic map, which can accurately identify all the equal-altitude lines and corresponding elevation values in the topographic map with the basic scale in dxf format, judge whether the fixed equal-altitude exists or not after summarizing, and effectively improve the detection efficiency of topographic map data.
The application aims to achieve the aim, and the aim is achieved by the following technical scheme:
a method for detecting a fixed constant altitude of a topographic map comprises the following steps:
opening a topographic map of a basic scale of the dxf format to be detected;
acquiring coordinate information and elevation values of each contour line in a topographic map, combining the coordinate information and the elevation values to generate detection information of each contour line, and adding the detection information of each contour line into a linked list;
grouping detection information of the contour lines in the linked list according to the areas described by the coordinate information of the contour lines;
in each group, calculating the contour distance of each group according to the elevation value of each contour line;
a fixed contour of the topography is determined based on the contour of each group.
Further, the obtaining the coordinate information and the elevation value of each contour line in the topographic map includes:
identifying, for each contour, a parent type and a subtype of the contour;
if the parent type of the contour is LWPLYLINE and the child type is AcDbPolyline, the elevation value of the contour is obtained and stored in a variable z by reading the data corresponding to the group code 38 in the LWPLYLINE type; the number of vertexes contained in the contour line is obtained and stored in a variable count by reading data corresponding to the group code 90 in the LWPLYLINE type; acquiring the x coordinate of each vertex of the contour line by reading the data corresponding to the group code 10 in the LWPILINE type, acquiring the y coordinate of each vertex of the contour line by reading the data corresponding to the group code 20 in the LWPILINE type, and storing the x and y coordinates of each vertex into a variable point;
otherwise, the next contour is identified.
Further, the step of combining the coordinate information and the elevation value to generate detection information of each contour line, and adding the detection information of each contour line to the linked list includes:
when the value of the variable count of the contour line is greater than 0, the value of the variable z is greater than 0, and the variable point is non-null, the variable point and the variable z of the contour line are combined into structural data, and the structural data is added into a linked list line_list as detection information of the contour line.
Further, the grouping of the detection information of the contour lines in the linked list according to the region described by the coordinate information of the contour lines includes the following steps:
step 1: judging whether the linked list line_list is empty or not; if yes, jumping to the step 5; if not, executing the next step;
step 2: removing detection information of a first group of contour lines in the linked list line_list, and storing the detection information into a variable line;
step 3: judging whether a packet exists currently or not; if not, adding line into the first group, and jumping to the step 1; if yes, executing the next step;
step 4: traversing each group circularly, if the contour line recorded in the variable line is surrounded or surrounded by a certain contour line in the current group, adding the variable line into the current group, otherwise, creating a new group, adding the variable line into a new group, and jumping to the step 1 after the addition is completed;
step 5: the packet is exited.
Further, in each group, the calculating the contour distance of each group according to the elevation value of each contour line includes:
reading a variable z of each contour line in each group to obtain all elevation values in the group;
sequencing all elevation values from big to small;
calculating the difference value of two adjacent elevation values;
judging whether all the differences are equal;
if yes, the difference value is equal-altitude of the group; if not, the detection fails.
Further, the determining the fixed contour distance of the topographic map according to the contour distance of each group includes:
judging whether the equal-height distances of each group are equal;
if yes, the equal-altitude distance is the fixed equal-altitude distance of the topographic map; if not, the topographic map does not have the firmware contour distance, and the detection fails.
Correspondingly, the application also discloses a system for detecting the fixed constant-altitude of the topographic map, which comprises the following steps:
the topographic map identification unit is used for opening the topographic map of the basic scale of the dxf format to be detected;
the data acquisition unit is used for acquiring coordinate information and elevation values of each contour line in the topographic map, combining the coordinate information and the elevation values to generate detection information of each contour line, and adding the detection information of each contour line into the linked list;
the data grouping unit is used for grouping the detection information of the contour lines in the linked list according to the areas described by the coordinate information of the contour lines;
a calculation unit that calculates, in each group, a contour distance of each group from an elevation value of each contour line;
and the judging unit is used for determining the fixed contour distance of the topographic map according to the contour distance of each group.
Correspondingly, the application also discloses a device for detecting the fixed constant-altitude of the topographic map, which comprises:
a memory for storing a computer program;
a processor for implementing the steps of the fixed contour detection method of a topography as defined in any of the preceding claims when executing said computer program.
Compared with the prior art, the application has the beneficial effects that: the application provides a method, a system and a device for detecting a fixed contour distance of a topographic map. And after the file is read, grouping the cached contour information according to the coordinate areas, so that each group is the contour data describing the same area and different heights. And for each group, sorting according to the magnitude of the elevation z value, and calculating the difference of every two adjacent elevation z values to obtain the same-altitude distance of the group. And after the equal-altitude distances of all the groups are obtained, summarizing and judging: if there is one and only one equal-height distance for each packet, and all the equal-height distances for the packets are equal, then there is a fixed equal-height distance in the dxf file, otherwise there is no.
The method and the system do not depend on third-party software, can accurately identify all contour lines and corresponding elevation values in the dxf format to summarize and judge whether fixed contour distances exist, are not easy to make mistakes, support cross-platform, facilitate batch processing and have high execution efficiency. The application can effectively improve the efficiency of quality detection and security identification work on dxf format topographic map data and simultaneously effectively improve the accuracy.
It can be seen that the present application has outstanding substantial features and significant advances over the prior art, as well as the benefits of its implementation.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present application, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method of an embodiment of the present application.
Fig. 2 is a flow chart of a method for detecting information packets of a contour line according to an embodiment of the present application.
Fig. 3 is a system configuration diagram of an embodiment of the present application.
Detailed Description
In order to better understand the aspects of the present application, the present application will be described in further detail with reference to the accompanying drawings and detailed description. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
The following explains key terms appearing in the present application.
1. Contour lines, contour distances:
the contour lines refer to a curve formed by connecting adjacent points with equal altitude in the national basic scale topographic map. The topography and topography are described by combining a plurality of contour lines with different heights. The height difference between the two contour lines is the contour distance between the two contour lines. According to the drawing specification of the national basic scale topographic map, the equal-altitude distance in one topographic map is required to be a specific value, and the equal-altitude distances required by the topographic maps of different scales are different.
2. dxf format:
the Dxf format is an open vector data format, which is a drawing exchange format generated and used by AutoCAD software, and generally stores all element data in ASCII code, so as to facilitate data interaction with other applications.
The Dxf format is numbered by different numerical values to describe information such as the type, value, name, etc. of the next line of stored data. These different numerical numbers are collectively referred to as group codes, and are stored exclusively in one line. Immediately below the group code is a row of data, storing the actual type, value and name data. If different group codes are regarded as KEYs and the data corresponding to the group codes are regarded as VALUE, the dxf format can be simply understood as a file containing a plurality of KEY-VALUE data pairs, and the KEYs and the VALUE respectively occupy one row for storage.
In dxf format, different data are stored in different segments, respectively, a HEADER segment, a class segment, a tabs segment, a BLOCKS segment, an entitis segment, an obscts segment, and a thumb segment.
When the dxf file is analyzed, the group codes are required to be read according to the rows, the data of the next row are analyzed according to the specific values of the group codes (which can be described by referring to the dxf format published by the AutoCAD official network), and the reading is circulated until the file is finished.
2. A multi-section line:
the multi-segment line is a solid type used in dxf format topographic map, is composed of lines and arcs, is a curve of arbitrary shape formed by connecting different points, and is stored in the sections of entitis. Contours in the national basic scale topography of dxf format are described by multi-segment line entities.
3. Elevation value:
elevation refers to a value representing altitude in a topographical map. The elevation value z refers to the corresponding elevation value described by the z value in the dxf format topographic map.
As shown in fig. 1, the application discloses a method for detecting a fixed constant-altitude distance of a topographic map, which comprises the following steps:
s1: and opening a topographic map of the basic scale of the dxf format to be detected.
In a specific embodiment, when the topographic map of the basic scale of the dxf format to be detected is opened, if the opening fails, the detection fails and the vehicle directly exits. If the opening is successful, the next step is continued.
S2: and acquiring coordinate information and elevation values of each contour line in the topographic map, combining the coordinate information and the elevation values by a root to generate detection information of each contour line, and adding the detection information of each contour line into a linked list.
For each contour, first, it is identified whether the parent type of the contour is lwpoly and the child type is acdbpoly. If not, the next contour line is identified until all contour lines are identified, and the process goes to S3. If yes, the elevation value of the contour line is obtained and stored in a variable z by reading the data corresponding to the group code 38 in the LWPILINE type; the number of vertexes contained in the contour line is obtained and stored in a variable count by reading data corresponding to the group code 90 in the LWPLYLINE type; the x coordinate of each vertex of the contour is obtained by reading the data corresponding to the group code 10 in the LWPLYLINE type, the y coordinate of each vertex of the contour is obtained by reading the data corresponding to the group code 20 in the LWPLYLINE type, and the x and y coordinates of each vertex are stored in the variable point.
In this case, it is necessary to confirm that the acquired contour information is valid information and to process the acquired information. That is, when the value of the variable count of the contour line is greater than 0, the value of the variable z is greater than 0, and the variable point is non-null, the variable point and the variable z of the contour line are combined into a data structure, and are added into the linked list line_list as the detection information of the contour line.
It should be specifically noted that, in this step, the data acquisition process is based on lwpoine entity type group codes, and the meanings of corresponding partial group codes in lwpoine entity types are as follows:
group code meaning comparison table of LWPLYLINE entity type
S3: and grouping the detection information of the contour lines in the linked list according to the areas described by the coordinate information of the contour lines.
The purpose of this step is to group all contours in the topography by region according to the region described by the contours. The grouping of the contours can be achieved according to the following idea:
for any given two contour lines A and B in the topographic map dxf file, when all the coordinates of the vertices in A are connected to form a curve, and all the coordinates in B can be enclosed (namely, all the coordinates in B are in the curve area), the representation that A and B are two contour lines which describe different heights on a certain area together can be called that A comprises B and B comprises A. I.e. the contours A, B belong to the same group.
If no other contour lines can enclose the coordinates in B, the contour line A, B describes two contour lines in different areas, i.e., the contour lines A, B are grouped differently.
Based on the above-mentioned ideas, in a specific embodiment, as shown in fig. 2, the method for grouping detection information of a contour line includes the following steps:
step 1: judging whether the linked list line_list is empty or not; if yes, jumping to the step 5; if not, executing the next step.
Step 2: and removing the detection information of the first group of contour lines in the linked list line_list, and storing the detection information into the variable line.
Step 3: judging whether a packet exists currently or not; if not, adding line into the first group, and jumping to the step 1; if yes, executing the next step.
As an example, in the present method, N packet linked lists may be defined before the grouping, and the packet linked lists are named as packet linked list 1, packet linked list 2 and … … packet linked list N in sequence, where each packet linked list is used to store the detection information of each contour line in the present group.
Therefore, if the current N packet linked lists are all empty linked lists, it may be determined that no detection information for the contour line is currently written into the packet linked list, and no packet currently exists. In the subsequent contour line grouping process, if the contour line is determined to belong to an existing grouping, writing the contour line into a corresponding grouping linked list; if it is determined that the contour line does not belong to the current existing packet, the detection information of the contour line is written into the first empty packet linked list.
Step 4: and traversing each group circularly, if the contour line recorded in the variable line is surrounded or surrounded by a certain contour line in the current group, adding the variable line into the current group, otherwise, creating a new group, adding the variable line into a new group, and jumping to the step 1 after the addition is completed.
As an example, in this step, the contour line recorded in the variable line may be determined by a ray method to be surrounded or enclosed by a certain contour line in the current group. The ray length is used to determine whether a point is inside a polygon.
Specifically, let the check information of the contour line recorded in the variable line be a, and the check information of a certain contour line in the current group be B. Whether A or B, the contour vertex coordinates are displayed on the electronic drawing, and can be regarded as a completely closed polygon.
First, coordinates of each contour vertex in A are extracted in turn, and whether the contour vertices are inside the polygon constructed according to B is judged by a ray method. If each of the vertices of the contour in A is inside a polygon constructed from B, it may be determined that the contour of the A record is enclosed by the contour of the B record. Otherwise, extracting coordinates of each contour vertex in the B in turn, and judging whether the contour vertices are inside the polygon constructed according to the A by a ray method. If each of the vertices of the contours in B are inside a polygon constructed from A, then it may be determined that the contours of the A record surround the contours of the B record.
Therefore, the contour line recorded in the variable line can be accurately judged to be surrounded or enclosed by a certain contour line in the current group by utilizing a ray method commonly used in the field.
Step 5: the packet is exited.
S4: in each group, the contour distance of each group is calculated according to the elevation value of each contour line.
In a specific embodiment, in each group, the variable z of each contour is first read to obtain all elevation values in the group. All elevation values are then sorted from big to small. At this time, the difference between the adjacent two elevation values is calculated. Finally, judging whether all the differences are equal; if yes, the difference value is equal-altitude of the group; if not, the detection fails.
S5: a fixed contour of the topography is determined based on the contour of each group.
In a specific embodiment, judging whether the equal-height distances of each group are equal; if yes, the equal-altitude distance is the fixed equal-altitude distance of the topographic map; if not, the topographic map does not have the firmware contour distance, and the detection fails.
Correspondingly, as shown in fig. 3, the application also discloses a system for detecting the fixed contour distance of the topographic map, which comprises the following steps: a topographic map identifying unit 1, a data collecting unit 2, a data grouping unit 3, a calculating unit 4 and a judging unit 5.
A topographic map identifying unit 1 for opening the topographic map of the basic scale of the dxf format to be detected.
The data acquisition unit 2 is configured to acquire coordinate information and elevation values of each contour line in the topographic map, combine the coordinate information and the elevation values to generate detection information of each contour line, and add the detection information of each contour line to the linked list.
And the data grouping unit 3 is used for grouping the detection information of the contour lines in the linked list according to the areas described by the coordinate information of the contour lines.
The calculation unit 4 calculates the contour distance of each group based on the elevation value of each contour line in each group.
A determining unit 5 for determining a fixed contour distance of the topographic map from the contour distances of each group.
Correspondingly, the application also discloses a device for detecting the fixed constant-altitude of the topographic map, which comprises:
a memory for storing a computer program;
a processor for implementing the steps of the fixed contour detection method of a topography as defined in any of the preceding claims when executing said computer program.
It will be apparent to those skilled in the art that the techniques of embodiments of the present application may be implemented in software plus a necessary general purpose hardware platform. Based on such understanding, the technical solution in the embodiments of the present application may be embodied essentially or in a part contributing to the prior art in the form of a software product stored in a storage medium such as a U-disc, a mobile hard disc, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk or an optical disk, etc. various media capable of storing program codes, including several instructions for causing a computer terminal (which may be a personal computer, a server, or a second terminal, a network terminal, etc.) to execute all or part of the steps of the method described in the embodiments of the present application. The same or similar parts between the various embodiments in this specification are referred to each other. In particular, for the terminal embodiment, since it is substantially similar to the method embodiment, the description is relatively simple, and reference should be made to the description in the method embodiment for relevant points.
In the several embodiments provided by the present application, it should be understood that the disclosed systems, and methods may be implemented in other ways. For example, the system embodiments described above are merely illustrative, e.g., the division of the elements is merely a logical functional division, and there may be additional divisions when actually implemented, e.g., multiple elements or components may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be through some interface, system or unit indirect coupling or communication connection, which may be in electrical, mechanical or other form.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
In addition, each functional module in the embodiments of the present application may be integrated in one processing unit, or each module may exist alone physically, or two or more modules may be integrated in one unit.
Similarly, each processing unit in the embodiments of the present application may be integrated in one functional module, or each processing unit may exist physically, or two or more processing units may be integrated in one functional module.
The application will be further described with reference to the accompanying drawings and specific embodiments. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application. Further, it will be understood that various changes and modifications may be made by those skilled in the art after reading the teachings of the application, and equivalents thereof fall within the scope of the application as defined by the claims.
Claims (5)
1. The method for detecting the fixed constant altitude of the topographic map is characterized by comprising the following steps of:
opening a topographic map of a basic scale of the dxf format to be detected;
acquiring coordinate information and elevation values of each contour line in a topographic map, combining the coordinate information and the elevation values to generate detection information of each contour line, and adding the detection information of each contour line into a linked list;
grouping detection information of the contour lines in the linked list according to the areas described by the coordinate information of the contour lines;
in each group, calculating the contour distance of each group according to the elevation value of each contour line;
determining a fixed contour distance of the topographic map according to the contour distance of each group;
the step of obtaining the coordinate information and the elevation value of each contour line in the topographic map comprises the following steps:
identifying, for each contour, a parent type and a subtype of the contour;
if the parent type of the contour is LWPLYLINE and the child type is AcDbPolyline, the elevation value of the contour is obtained and stored in a variable z by reading the data corresponding to the group code 38 in the LWPLYLINE type; the number of vertexes contained in the contour line is obtained and stored in a variable count by reading data corresponding to the group code 90 in the LWPLYLINE type; acquiring the x coordinate of each vertex of the contour line by reading the data corresponding to the group code 10 in the LWPILINE type, acquiring the y coordinate of each vertex of the contour line by reading the data corresponding to the group code 20 in the LWPILINE type, and storing the x and y coordinates of each vertex into a variable point;
otherwise, identifying the next contour line;
the step of generating detection information of each contour line after combining the coordinate information and the elevation value and adding the detection information of each contour line into a linked list comprises the following steps:
when the value of the variable count of the contour line is greater than 0, the value of the variable z is greater than 0, and the variable point is non-null, combining the variable point and the variable z of the contour line into structural data, and adding the structural data into a linked list line_list as detection information of the contour line;
the method for grouping the detection information of the contour lines in the linked list according to the areas described by the coordinate information of the contour lines comprises the following steps:
step 1: judging whether the linked list line_list is empty or not; if yes, jumping to the step 5; if not, executing the next step;
step 2: removing detection information of a first group of contour lines in the linked list line_list, and storing the detection information into a variable line;
step 3: judging whether a packet exists currently or not; if not, adding line into the first group, and jumping to the step 1; if yes, executing the next step;
step 4: traversing each group circularly, if the contour line recorded in the variable line is surrounded or surrounded by a certain contour line in the current group, adding the variable line into the current group, otherwise, creating a new group, adding the variable line into a new group, and jumping to the step 1 after the addition is completed;
step 5: the packet is exited.
2. The method for detecting a fixed contour distance of a topographic map according to claim 1, wherein in each group, a contour distance of each group is calculated according to an elevation value of each contour line, comprising:
reading a variable z of each contour line in each group to obtain all elevation values in the group;
sequencing all elevation values from big to small;
calculating the difference value of two adjacent elevation values;
judging whether all the differences are equal;
if yes, the difference value is equal-altitude of the group; if not, the detection fails.
3. The method for detecting a fixed contour distance of a topographic map according to claim 2, wherein said determining a fixed contour distance of the topographic map from the contour distance of each group comprises:
judging whether the equal-height distances of each group are equal;
if yes, the equal-altitude distance is the fixed equal-altitude distance of the topographic map; if not, the topographic map does not have a fixed constant altitude, and the detection fails.
4. A fixed contour detection system for a topography, comprising:
the topographic map identification unit is used for opening the topographic map of the basic scale of the dxf format to be detected;
the data acquisition unit is used for acquiring coordinate information and elevation values of each contour line in the topographic map, combining the coordinate information and the elevation values to generate detection information of each contour line, and adding the detection information of each contour line into the linked list;
the data grouping unit is used for grouping the detection information of the contour lines in the linked list according to the areas described by the coordinate information of the contour lines;
a calculation unit that calculates, in each group, a contour distance of each group from an elevation value of each contour line;
a determining unit for determining a fixed contour distance of the topographic map according to the contour distance of each group;
the data acquisition unit is specifically used for:
identifying, for each contour, a parent type and a subtype of the contour;
if the parent type of the contour is LWPLYLINE and the child type is AcDbPolyline, the elevation value of the contour is obtained and stored in a variable z by reading the data corresponding to the group code 38 in the LWPLYLINE type; the number of vertexes contained in the contour line is obtained and stored in a variable count by reading data corresponding to the group code 90 in the LWPLYLINE type; acquiring the x coordinate of each vertex of the contour line by reading the data corresponding to the group code 10 in the LWPILINE type, acquiring the y coordinate of each vertex of the contour line by reading the data corresponding to the group code 20 in the LWPILINE type, and storing the x and y coordinates of each vertex into a variable point;
otherwise, identifying the next contour line;
when the value of the variable count of the contour line is greater than 0, the value of the variable z is greater than 0, and the variable point is non-null, combining the variable point and the variable z of the contour line into structural data, and adding the structural data into a linked list line_list as detection information of the contour line;
the data packet unit is specifically configured to perform the following steps:
step 1: judging whether the linked list line_list is empty or not; if yes, jumping to the step 5; if not, executing the next step;
step 2: removing detection information of a first group of contour lines in the linked list line_list, and storing the detection information into a variable line;
step 3: judging whether a packet exists currently or not; if not, adding line into the first group, and jumping to the step 1; if yes, executing the next step;
step 4: traversing each group circularly, if the contour line recorded in the variable line is surrounded or surrounded by a certain contour line in the current group, adding the variable line into the current group, otherwise, creating a new group, adding the variable line into a new group, and jumping to the step 1 after the addition is completed;
step 5: the packet is exited.
5. A fixed contour detection device for a topography, comprising:
a memory for storing a computer program;
a processor for implementing the steps of the fixed contour detection method of a topography as claimed in any of claims 1 to 3 when executing said computer program.
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