A CAD arc segment coordinate conversion method, device and storage device

Abstract

The application discloses a CAD arc segment coordinate conversion method, equipment and a storage device, and the method comprises the following steps: step 1, judging whether the CAD graphic entity read by the object memory type is an arc segment object; if yes, entering step 2, otherwise reading the next CAD graphic entity; 2, detecting whether the entity is an arc segment circle, if yes, performing arc segment circle coordinate conversion processing on the entity, entering step 5, otherwise entering step 3; 3, detecting whether the entity is an arc segment short line, if yes, performing arc segment short line coordinate conversion processing on the entity, entering step 5, otherwise entering step 4; 4, performing ordinary arc coordinate conversion processing on the graphic entity according to the ordinary arc, and obtaining the converted arc segment; 5, saving the converted arc segment. The application can solve the problem that the work of the operator is not standardized, and ensure that the result of the geographic graphic entity coordinate conversion is normally displayed, and the arc line and the adjacent line are normally connected.

Description

Technical Field

[0001] This invention relates to the field of coordinate space conversion in drawings, and more particularly to a method, device, and storage device for CAD arc segment coordinate conversion. Background Technology

[0002] Currently, the plane coordinate system used for historical surveying and planning data is mostly the 1980 Xi'an Coordinate System, and the elevation system is the 1985 National Elevation Datum, using local projection zones in the Gauss-Kruger coordinate system. When processing historical data, spatial coordinate transformation is required for the basic topographic maps and historical planning results data. The transformation model generally uses a seven-parameter model or a four-parameter plane model to determine the transformation parameters, especially the determination of the Bursha seven parameters between the 2000 National Geodetic Coordinate System and the 1980 Xi'an Coordinate System.

[0003] Topographic maps and planning drawings are generally stored in CAD format. CAD is a graphical representation storage database. Unlike the basic primitives of conventional GIS, CAD includes complex function-simulated primitive types such as circles, arcs, and splines. Arcs are important drawing elements when depicting terrain, often used to represent turning areas such as roads, rivers, and corridors. The handling of arcs presents technical challenges to general spatial projection coordinate transformations.

[0004] Furthermore, the operational habits of data production workers, such as drawing circles or short lines on arcs, may not cause problems in terms of graphic visualization and accuracy checking. However, if no special handling is done during arc coordinate transformation, issues such as reversed arc direction and broken arc points and connecting lines after magnification may occur due to floating-point precision problems. Summary of the Invention

[0005] To address the shortcomings of conventional topographic map CAD coordinate transformation methods, which rely solely on transforming the endpoints and center points of arc segments and reconstructing the arc segments, the accuracy of the transformation results is insufficient. Furthermore, these methods fail to handle issues such as arc segment openings and breaks in connection caused by drawing circles or short lines on arc segments. Therefore, this invention proposes a CAD arc segment coordinate transformation method, device, and storage device. The method includes:

[0006] S1. Determine whether the CAD drawing entity being read is an arc segment object by checking its memory type; if so, record it as drawing entity E. arc If the condition is not met, proceed to step S2; otherwise, read the next CAD drawing entity and repeat step S1.

[0007] S2, Detect graphic entity E arc Is it an arc segment to draw a circle? If so, then for graphic entity E... arcPerform coordinate transformation for arc-to-circle drawing. If the transformation is successful, proceed to step S5; otherwise, proceed to step S3.

[0008] S3, Detect graphic entity E arc Is it a short line drawn for an arc segment? If so, then for graphic entity E... arc Perform coordinate transformation processing for drawing short arc lines. If the processing is successful, proceed to step S5; otherwise, proceed to step S4.

[0009] S4. Perform ordinary arc coordinate transformation on the graphic entity according to ordinary arc to obtain the transformed arc segment;

[0010] S5. Save the converted arc segment.

[0011] A storage device that stores instructions and data for implementing a CAD arc segment coordinate transformation method.

[0012] A CAD arc segment coordinate transformation device includes: a processor and a storage device; the processor loads and executes instructions and data in the storage device to implement a CAD arc segment coordinate transformation method.

[0013] The beneficial effects provided by this invention are: it can effectively handle problems such as drawing circles with arcs, drawing short line segments with arcs, and arc segments with extremely small radian values ​​in the arc segment data of conventional CAD drawings due to non-standard operator operations. In the geographic projection spatial coordinate ellipsoid conversion, due to insufficient floating-point calculation precision, the conversion results may have abnormal arc segment display, arc segment direction reversal, and disconnection between arc segments and adjacent line segments. It ensures that the converted results are displayed normally and that the arcs are connected normally to adjacent lines. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0015] Figure 2 It is implemented using a 1:1000 basic topographic map;

[0016] Figure 3 The issue stems from an anomaly in the coordinate transformation of the basic topographic map, specifically in the arc segment processing.

[0017] Figure 4 In basic topographic maps, cartographers use arcs to draw circular symbol objects.

[0018] Figure 5 The circular symbol object drawn with an arc segment has a gap when actually enlarged;

[0019] Figure 6 It uses a small arc segment connecting the road edge line to make a turn;

[0020] Figure 7The result is a base topographic map converted using this invention.

[0021] Figure 8 This is a schematic diagram of the hardware device working in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0023] First, the relevant functions used in this invention (obtained from the software) are uniformly described as follows:

[0024] (1) The coordinate transformation function is F transcoord Both input and output are coordinate points;

[0025] (2) The function for calculating the distance between points in a plane is F. distance The input is two coordinate points, and the output is the distance value.

[0026] (3) Function F for calculating the rectangular range of CAD graphic entities boundsCalculator The input is a CAD graphic object, and the output is a range rectangle.

[0027] (4) Function F for calculating the coordinates of arcs / points on circles calcArcPtByAngle The input is the center and radius of the arc, and the angle of the point to be calculated. The return value is the coordinates of the point.

[0028] (5) Function F for calculating the intersection point of two intersecting circles calcCircleInsectPt The input is the center point and radius of the two circles, and the output is the coordinates of the two intersection points of the two circles.

[0029] (6) Function F for calculating the arc angle of an arc point calcAnglebyArcPt The input is the center and radius of the arc, as well as the coordinates of a point on the arc. The output is the angle of the point on the arc, in the range [0, 2π].

[0030] (7) Function F for calculating the coordinates of the midpoint of a circular arc segment calcArcCenterPt The input is the center and radius of the arc, as well as the starting and ending angles of the arc. The output is the coordinates of the midpoint of the arc.

[0031] (8) Function F for calculating the center of an arc calcCenterByArc3Pt The input is three points on the arc of the circle, and the output is the coordinates of the center point of the arc.

[0032] The content of this invention is described below:

[0033] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the method flow of the present invention.

[0034] This invention provides a CAD arc segment coordinate transformation method, device, and storage device. The method includes:

[0035] S1. Determine whether the CAD drawing entity being read is an arc segment object by checking its memory type; if so, record it as drawing entity E. arc If the condition is not met, proceed to step S2; otherwise, read the next CAD drawing entity and repeat step S1.

[0036] It should be noted that in general programming, the memory type of the object is compared to determine whether the read CAD drawing entity object E is an arc segment object. When the drawing entity object is an arc segment object, it is denoted as E. arc The center point C of the arc segment has coordinates (C). x C y Let the radius be R and the starting angle of the arc segment be A. start The range is [0, 2π], the unit is radians, and the ending angle of the arc segment is denoted as A. end The range is [0, 2π], and the unit is radians. Continue to execute step S2; when the graphic entity object is not an arc segment object, end the E graphic entity processing and proceed to the next graphic entity processing.

[0037] S2, Detect graphic entity E arc Is it an arc segment to draw a circle? If so, then for graphic entity E... arc Perform coordinate transformation for arc-to-circle drawing. If the transformation is successful, proceed to step S5; otherwise, proceed to step S3.

[0038] In step S2, the graphic entity E is detected. arc The specific process of drawing a circle by considering whether it is an arc segment is as follows: Starting angle A start With end angle A end The absolute value of the difference A delta That is: A delta =abs(A start -A end ), A delta >0, A delta The unit is radians; according to A delta Threshold size A threshold When comparing, when A delta >A threshold That is, E arc It's not about drawing a circle using arcs.

[0039] It should be noted that in step S2, the graphic entity E... arc The specific process of performing coordinate transformation for drawing circles from arc segments is as follows:

[0040] S21. Calculate the solid E′ after coordinate transformation for drawing a circle from an arc segment. arc1 The center position is C1′, where C1′=Ftranscoord (C); C is the graphic entity E. arc The central position; F transcoord This is a coordinate transformation function;

[0041] S22. Calculation of the radius of the transformed arc segment: E′ after transformation. arc1 Radius R1′, Sampling E arc Temporary point P on temp1 P temp1 coordinates P temp1 (x,y)=(C x +R,C y R is a graphical entity E arc radius; C x C y Let C be the coordinate value; then the point P after coordinate transformation... t ′ emp1 =F transcoord (P temp1 ),R1′=F distance (C1′,P t ′ emp1 ); where F distance This is a function for calculating the distance between points in a plane.

[0042] S23, Update E′ after conversion arc1 The arc parameters are: center C1′, radius R1′, and starting angle A′. start1 With the ending angle A′ end1 Keep the original value, i.e., A′. start1 =A start And A′ end1 =A end .

[0043] S3, Detect graphic entity E arc Is it a short line drawn for an arc segment? If so, then for graphic entity E... arc Perform coordinate transformation processing for drawing short arc lines. If the processing is successful, proceed to step S5; otherwise, proceed to step S4.

[0044] In step S3, the graphic entity E is detected. arc The specific process for determining whether to draw a short line for an arc segment is as follows: Calculate the graphic entity E arc Outer rectangular range B extent B extent =F boundsCalculator (E arc ), where F boundsCalculator Functions for calculating the rectangular range of CAD drawing entities; B extent The width value is L width and height value L height ; Determine E arcWhether it is a short-term move, L width and L height With threshold L threshold Compare, if L width >L threshold And L width >L threshold That is, to represent the graphic entity E arc Draw a short line instead of an arc segment; otherwise, it represents the graphic entity E. arc It is an arc segment drawn as a short line.

[0045] It should be noted that in step S3, the graphic entity E... arc The specific process for performing coordinate transformation to draw short lines from arcs is as follows:

[0046] S31. The graphic entity after coordinate transformation for drawing short arc segments is E′. arc2 ; Calculate the graphic entity E under the short line drawing type of arc segment. arc Arc segment starting point P start2 Coordinates and endpoint P end2 , where P sstart2 =F calcArcPtByAngle (C,R,A start ),P end2 =F calcArcPtByAngle (C,R,A end );F calcArcPtByAngle Function for calculating the coordinates of points on an arc / circle;

[0047] S32, To E arc The center point C of the circle, the starting point p of the arc segment start and the endpoint p of the arc segment end Perform coordinate transformation, resulting in C′. temp2 , P′ start2 , P′ end2 Where C′ temp2 =F transcoord (C), P′ start2 =F transcoord (P start2 ), P′ end1 =F transcoord (P end2 );

[0048] S33. Calculate the new center C2′ of the transformed arc segment;

[0049] It should be noted that the specific process of step S33 is as follows:

[0050] S331, with P′ as the center of the circle. start2 , P′ end2 Construct two circles, with their radii set to R;

[0051] S332. Calculate the intersection point P of the two circles. circleIntect1 and P circleIntect2 , of which (P circleIntect1 ,P circleIntect2 ) = F calcCircleInsectPt (P′ start1 ,R,P′ end1 ,R).

[0052] S333, Calculate the intersection point P circleIntect1 P circleIntect2 Distance L from C2′ circleIntect1 and L circleIntect2 L circleIntect1 =F distance (C′ temp2 ,P circleIntect1 ), L circleIntect2 =F distance (C′ temp2 ,P circleIntect2 );

[0053] S334. Calculate the new center C2′ after the arc segment transformation; when L circleIntect1 <L circleIntect2 Then C2′=P circleIntect1 When L circleIntect1 ≥L circleIntect2 Then C2′=P circleIntect2 .

[0054] S34. Calculate the starting angle A′ of the converted arc segment. start2 and ending angle A′ end2 , where A′ start2 =F calcAnglebyArcPt (C2′,R,P′ start2 ),A′ end2 =F calcAnglebyArcPt (C2′,R,P e ′ nd2 );F calcAnglebyArcPt This is a function for calculating the arc angle at a point on a circular arc.

[0055] S4. Perform ordinary arc coordinate transformation on the graphic entity according to ordinary arc to obtain the transformed arc segment;

[0056] It should be noted that the specific process of performing ordinary circular arc coordinate transformation in step S4 is as follows:

[0057] S41. The graphic entity after ordinary circular arc coordinate transformation is E′. arc3 ; Calculate the starting point P of the arc segment of the graphic entity Earc under the ordinary arc type. start3 Coordinates, End Point P end3 The coordinates of the midpoint P of the arc segment arcCenterPt , where Pstart3 =F calcArcPtByAngle (C,R,A start ),P end3 =F calcArcPtByAngle (C,R,A end ), P arcCenterPt =F calcArcCenterPt (C,R,A start A end ); Calculate the coordinate transformation result P′ start3 , P′ end3 , P′ arcCenterPt , where P′ start3 =F transcoord (P start3 ), P′ end3 =F transcoord (P end3 ), P′ arcCenterPt =F transcoord (P arcCenterPt );

[0058] S42. Calculate the center of the transformed arc segment as C3′, where C3′=F calcCenterByArc3Pt (P′ start3 ,P′ end3 ,P′ arcCenterPt ); Calculate E′ arc3 The radius R3′, the starting angle A′ start3 End angle A′ end3 , where R3′=F distance (C′,P′ start3 ),A′ start3 =F calcAnglebyArcPt (C′,R′,P′ start3 ),A′ end3 =F calcAnglebyArcPt (C′,R′,P′ end3 ).

[0059] S43, Update E′ after conversion arc3 The arc parameters are: center C3′, radius R3′, and starting angle A′. start3 The ending angle is A′ end3 .

[0060] S5. Save the converted arc segment.

[0061] As one embodiment, this invention specifically utilizes CadLib v4.0.37.140 to develop components, which can independently load and process CAD files without the AutoCAD runtime environment. The implemented CAD file is a standard terrain. Figure 1Map sheet 1000, Beijing 54 ellipsoid Gaussian 114.875° projection, converted to CGCS2000 ellipsoid Gaussian 114.875° projection, original map sheet as follows: Figure 2 As shown, Figure 3 To address the issue of reversed arc direction after conversion using the conventional three-point (arc start point, arc end point, and arc midpoint) conversion method, the specific steps include:

[0062] In step S1, it is determined whether the read CAD drawing entity is an arc object. The DxfModel object from the CadLib library is used to load the DxfEntity collection of all CAD entity objects. DxfEntity is the base class for all types of primitives. By iterating through each member of DxfEntityCollection, a reference to the DxfEntity base class object for each drawing can be obtained. Determining whether a drawing object is of arc type only requires type checking using the object's entity.

[0063] It should be noted here that the arc type determination needs to be placed before the circle type DxfCircle in the entire process, because DxfArc inherits from DxfCircle.

[0064] In step S2, it is detected whether the arc segment is used to draw a circle. When the operator uses an arc segment to draw a circle, if... Figure 4 It generally represents an isolated feature, but in reality, an arc has a very small opening. Figure 5 As shown in the diagram. The process involves determining the difference between the starting and ending angles of the two opening points.

[0065] In step S21, the absolute value of the difference between the starting angle and the ending angle of the current arc segment is calculated and compared with the threshold of 0.001. When the angle difference is greater than the threshold, proceed directly to step S3; when the angle is less than the threshold, draw a circle for the arc segment and continue with subsequent coordinate transformation processing.

[0066] In step S22, the arc coordinate transformation is processed by performing transformation calculations on the arc start point, end point, and midpoint, and then using the three-point arc construction method to generate the arc center, radius, arc start angle, and arc end angle.

[0067] In step S23), the center, radius, starting angle and ending angle values ​​of the arc segment after conversion calculated in step S22 are written back to the parameters of the converted arc segment object. Then, step S5 is executed to complete the saving of the arc segment object data.

[0068] In step S3, it is detected whether the arc object is a short line. For ease of calculation, the BoundsCalculator object of the CadLib library is used to calculate the bounding rectangle of the primitive to obtain the length and width of the graphic.

[0069] In step S31, the length and width of the rectangle enclosing the arc segment are used to determine whether the arc segment is a short line, with a threshold set to 0.5 meters. When both the length and width of the enclosing rectangle are greater than 0.5 meters, the arc segment is determined not to be a short line, and the process proceeds directly to step S4. When either the length or width of the enclosing rectangle is less than 0.5 meters, the arc segment is determined to be a short line, and the process proceeds to the next coordinate transformation step. A short arc segment is as follows: Figure 6 As shown, the left arc segment is 0.70 meters long, and the width and height of the enclosing rectangle are 0.32 meters and 0.52 meters, respectively; the right arc segment is 0.25 meters long, and the width and height of the enclosing rectangle are 0.194 meters and 0.045 meters, respectively.

[0070] In step S32, the parameters of the arc segment after transformation are calculated. Since the arc segment is a short line segment, after transformation, it will be ensured that the two endpoints of the arc segment and their possible connecting lines can remain connected after transformation. Therefore, a) the two endpoints are control points and their coordinates are transformed. b) the current center point of the arc segment is also used as an important reference point and its coordinates are transformed. c) the radius of the original arc segment is retained. d) the intersection circle operation is performed using the two endpoints and the radius to obtain two intersection points. e) the intersection point that is closest to the reference point after the transformation of the arc segment center point is the center of the transformed arc segment. f) the center, radius, starting angle and ending angle values ​​are calculated based on the coordinates of the transformed center, radius, starting point and ending point.

[0071] In step S33, the center, radius, starting angle, and ending angle values ​​of the converted arc segment calculated in step S33 are written back to the parameters of the converted arc segment object. Then, step S5 is executed to complete the saving of the arc segment object data.

[0072] In step S4, since no processing was performed in steps S2 and S3, the current arc segment is determined to be a normal arc segment.

[0073] In step S41, coordinate transformation is performed on three points on the arc segment: the starting point, the ending point, and the midpoint of the arc segment. The three points obtained after the transformation are the three points on the transformed arc segment.

[0074] In step S42, the center, radius, starting angle, and ending angle of the transformed arc segment are calculated based on the three arc points converted in step S41 using the three-point arc construction method.

[0075] In step S43, the center, radius, starting angle, and ending angle values ​​of the arc segment after conversion calculated in step S42 are written back to the parameters of the converted arc segment object. Then, step S5 is executed to complete the saving of the arc segment object data.

[0076] In step S5, the data write-back and save interface in the CadLib library is called to complete the graphic data conversion and saving. The conversion result is as follows: Figure 7 As shown, the arc segment conversion anomaly issue has been eliminated.

[0077] Please see Figure 8 , Figure 8 This is a schematic diagram of the hardware device in operation according to an embodiment of the present invention. The hardware device specifically includes: a CAD arc coordinate conversion device 401, a processor 402, and a storage device 403.

[0078] A CAD arc segment coordinate conversion device 401: The device 401 implements the CAD arc segment coordinate conversion method.

[0079] Processor 402: The processor 402 loads and executes the instructions and data in the storage device 403 to implement the CAD arc coordinate transformation method.

[0080] Storage device 403: The storage device 403 stores instructions and data; the storage device 403 is used to implement the CAD arc segment coordinate transformation method.

[0081] The beneficial effects of this invention are: it can effectively handle problems such as drawing circles with arcs, drawing short line segments with arcs, and arc segments with extremely small radian values ​​in the arc segment data of conventional CAD drawings due to non-standard operator operations. In the geographic projection spatial coordinate ellipsoid conversion, due to insufficient floating-point calculation precision, the conversion results may have abnormal arc segment display, arc segment direction reversal, and disconnection between arc segments and adjacent line segments. It ensures that the converted results are displayed normally and that the arcs are connected normally to adjacent lines.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A CAD arc segment coordinate transformation method, characterized in that: Includes the following steps: S1. Determine whether the read CAD drawing entity is an arc segment object by checking its memory type; if so, record it as a drawing entity. E arc If the condition is not met, proceed to step S2; otherwise, read the next CAD drawing entity and repeat step S1. S2, Detect graphic entities E arc Is it drawing a circle for an arc segment? If so, then for the graphic entity... E arc Perform coordinate transformation for arc-to-circle drawing. If the transformation is successful, proceed to step S5; otherwise, proceed to step S3. S3, Detect graphic entities E arc Is it a short line drawn for an arc segment? If so, then for the graphic entity... E arc Perform coordinate transformation processing for drawing short arcs. If the processing is complete, proceed to step S5; otherwise, proceed to step S4. S4. Perform ordinary arc coordinate transformation on the graphic entity according to ordinary arc to obtain the transformed arc segment; S5. Save the converted arc segment; In step S2, the graphic entity is detected. E arc The specific process of drawing a circle by considering whether it is an arc segment is as follows: Starting angle With the end angle absolute value of the difference ,Right now: , , The unit is radians; according to Threshold size When comparing, , that is to say It's not about drawing a circle using arcs; In step S3, the graphic entity is... E arc The specific process for performing coordinate transformation to draw short lines from arcs is as follows: S31. The graphic entity after coordinate transformation for drawing short lines of arc segments is: ; Calculate the graphic entity under the short line type of arc segment drawing. E arc arc starting point Coordinates and endpoint ,in , ; Function for calculating the coordinates of points on an arc / circle; S32, to The center point arc starting point and the end point of the arc segment Perform coordinate transformation, the transformed values ​​are as follows: , , ;in , , ; S33. Calculate the new center of the arc segment after transformation. ; S34. Calculate the starting angle of the transformed arc segment. and the ending corner ,in , ； This is a function for calculating the arc angle at a point on a circular arc.

2. The CAD arc segment coordinate transformation method as described in claim 1, characterized in that: In step S2, the graphic entity is... E arc The specific process of coordinate transformation for drawing circles from arc segments is as follows: S21. Calculate the solid after coordinate transformation for drawing a circle from an arc segment. central position ,in ; C For graphic entities E arc The central position; This is a coordinate transformation function; S22. Calculation of the radius of the converted arc segment. radius ,sampling temporary points , coordinates , R For graphic entities E arc The radius; C x , C y Let C be the coordinate value; then the point after coordinate transformation , ;in This is a function for calculating the distance between points in a plane. S23, After Update and Conversion The arc parameters, with the center being , radius is Starting angle With the end angle Retain the original value, that is and .

3. The CAD arc segment coordinate transformation method as described in claim 1, characterized in that: Detecting graphic entities in step S3 E arc The specific process for determining whether to draw a short line for an arc segment is as follows: Calculate the graphic entity Outer rectangular range ,in ,in, The width value is and height value ;judge Whether it is a short-term trade or not, and With threshold If a comparison is made, and That is, to represent graphic entities Draw a short line instead of an arc; otherwise, it represents a graphic entity. It is an arc segment drawn as a short line.

4. The CAD arc segment coordinate transformation method as described in claim 1, characterized in that: The specific process of step S33 is as follows: S331, with the center of each circle as... , Construct two circles, with their radii set to... ; S332, Calculate the intersection point of the two circles. and ,in ; S333, Calculate the intersection point , and distance and ,in ， ； S334. Calculate the new center of the circle after the arc segment transformation. ;when ,but ;when ,but .

5. The CAD arc segment coordinate transformation method as described in claim 1, characterized in that: The specific process of performing ordinary circular arc coordinate transformation in step S4 is as follows: S41, The graphic entity after ordinary circular arc coordinate transformation is: ; Calculate the graphic entity under the ordinary arc type. Earc arc starting point Coordinates, End Point midpoint coordinates of the arc segment ,in , ， ; Calculate the coordinate transformation results , , ,in , , ; S42. Calculate the center of the transformed arc segment. ,in ; calculate radius Starting angle End corner ,in , , ; S43, After Update and Conversion The arc parameters, with the center being , radius is The starting angle is The ending angle is .

6. A storage device, characterized in that: The storage device stores instructions and data for implementing a CAD arc segment coordinate transformation method as described in any one of claims 1 to 5.

7. A CAD arc segment coordinate transformation device, characterized in that: include: A processor and a storage device; the processor loads and executes instructions and data in the storage device to implement the CAD arc coordinate transformation method according to any one of claims 1 to 5.

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