Draw Curve

Function Description

The application supports multiple types of curves: Bezier curve, B-Spline curve, Cardinal curve, free curve, and geodesic.

Function Entry

  • Edit Data tab > Object Drawing group > Line drop-down list > Curve.

Instructions

Draw a Bezier curve

A Bezier curve is controlled by two start nodes and two end nodes that are not on the curve, and the intermediate points on the curve are fitted by other control points on the curve. At least six control points are required to complete drawing a Bezier curve.

  1. In the Edit Data tab, in the Object Drawing group, click the Line drop-down button and select the Bezier Curve option. The Bezier curve cursor appears.
  2. Move the mouse to the map. As the mouse moves, the parameter input box behind it displays the current mouse position coordinates in real time. Enter the coordinates of the first control point of the Bezier curve in the parameter input box (you can switch between the two parameter input boxes by pressing Tab), and then press Enter to confirm.
  3. Enter the coordinates of the second to fourth control points in the same way. The coordinates of the first four control points determine the direction of the Bezier curve.
  4. Enter the coordinates of the fifth control point on the curve. At this point, a blue dashed line appears between the third and fourth control points, representing the first fitted segment on the Bezier curve.
  5. Continue to enter the coordinates of the sixth control point to draw the second segment of the Bezier curve.
  6. Repeat the previous step to continue drawing other segments of the Bezier curve.
  7. Click the right mouse button to finish the current drawing.

B-Spline Curve

A B-Spline curve is drawn using the first and last control points on the curve and the intermediate control points that are not on the curve. Other points on the curve are fitted based on the intermediate control points. At least four control points are required to complete drawing a B-Spline curve.

  1. In the Edit Data tab, in the Object Drawing group, click the Line drop-down button and select the B-Spline Curve option. The B-Spline curve cursor appears.
  2. Move the mouse to the map. As the mouse moves, the parameter input box behind it displays the current mouse position coordinates in real time. Enter the coordinates of the first control point of the curve in the parameter input box (you can switch between the two parameter input boxes by pressing Tab), and then press Enter to confirm.
  3. Enter the coordinates of the second control point on the curve.
  4. Enter the coordinates of the third control point on the curve. At this point, a blue dashed line appears between the first and third control points, representing the first segment of the B-Spline curve.
  5. Enter the coordinates of the fourth control point on the curve. At this point, a blue dashed line appears between the third and fourth control points, representing the second segment of the B-Spline curve.
  6. Repeat the previous step to continue drawing other segments of the B-Spline curve.
  7. Click the right mouse button to finish the current drawing.

Cardinal Curve

A Cardinal curve is drawn by determining the control points on the curve, and other points on the curve are fitted based on all control points. At least three control points are required to complete drawing a Cardinal curve.

  1. In the Edit Data tab, in the Object Drawing group, click the Line drop-down button and select the Cardinal Curve option. The Cardinal curve cursor appears.
  2. Move the mouse to the map. As the mouse moves, the parameter input box behind it displays the current mouse position coordinates in real time. Enter the coordinates of the first control point of the curve in the parameter input box (you can switch between the two parameter input boxes by pressing Tab), and then press Enter to confirm.
  3. Enter the coordinates of the second control point in the same way. A blue dashed line appears between these two points.
  4. Move the mouse and enter the coordinates of the third control point. A second blue dashed line appears between the second and third control points.
  5. Click the right mouse button to finish the current drawing.

Free Curve

A free curve is a curve obtained by freely dragging and drawing. Drawing a free curve is very useful for creating irregular boundaries or tracing with a digitizer.

  1. In the Edit Data tab, in the Object Drawing group, click the Line drop-down button and select the Free Curve option. The free curve cursor appears.
  2. Move the cursor to the location where you want to create the free curve, click and hold the left mouse button, and then move the mouse. A curve that follows the movement trajectory of the cursor will be drawn on the map.
  3. After completing the drawing, click the right mouse button to finish the operation.

Geodesic

A geodesic is a curve that follows the curvature of the Earth's surface, and it most accurately represents the shortest distance between any two points on the Earth's surface. It is often used to draw global navigation or aviation routes. Global Pan must be enabled to draw a geodesic.

The following uses drawing an aviation route as an example to describe the operation steps in detail:

  1. Open the World.smwu workspace in the sample data, open "World Map_Day" in the map, add the route line dataset to the map, and enable editing of the line data.
  2. In the Edit Data tab, in the Object Drawing group, click the Line drop-down button and select the Geodesic option. Move the mouse to the map to start drawing.
  3. Click the left mouse button at the start and end points of the route. After drawing, click the right mouse button to finish the current line object. After drawing, set the layer style to obtain the following result image:
Figure: Airline Route