Function Description

The polygon command is used to create a polygon. The polygons mentioned here include arbitrary polygons, regular polygons, orthogonal polygons, etc. Polygons are one of the most commonly used surface objects, often used to represent closed surface features such as administrative regions, soil, vegetation, lakes, etc. They can also represent some special types of surface features in geography, such as islands, rings, enclaves, etc.

Function Entry

• Features tab -> Objects group -> Polygon drop-down list -> Polygon.

Operation Instructions

Drawing a Polygon by Inputting Coordinate Values

The process of drawing a polygon is as shown in the following figure:

The process of drawing a polygon by holding down the Q key is as shown in the following figure:

Drawing a Polygon by Length and Angle

1. In the Features tab, in the Objects group, click the Polygon drop-down button, and select the Polygon(Length, Angle) option.
2. Move the mouse to the map, and you can see that as the mouse moves, the coordinate values of the point are displayed in real-time in the following parameter box. Enter the coordinate values of the first node of the polygon in the box (you can switch between two parameter input boxes by pressing the Tab key) and then press Enter to determine the starting position of the polygon.
3. Move the mouse, and you can see that as the mouse moves, the length of the line connecting the mouse position to the previous control point and its angle with the positive direction of the X-axis are displayed in real-time on the map. Type the length value and angle value in the parameter input boxes (you can switch between two parameter input boxes by pressing the Tab key), and press Enter to execute the input and determine the drawing of the first segment of the polygon.
4. Enter the distance (length) between the next node and the previous node, and the angle between the connecting line and the positive direction of the X-axis (you can switch between two parameter input boxes by pressing the Tab key), then press Enter to draw the next segment of the polygon.
5. Repeat the above steps to continue drawing other segments of the polygon.
6. Right-click the mouse to end the current drawing operation.

Drawing a Regular Polygon

The drawing process of a regular polygon is as shown in the following figure:

Specify the center point of the regular polygon	Specify the length and angle of the regular polygon	Result diagram of the regular polygon

1. In the Features tab, in the Objects group, click the Polygon drop-down button, and select the Regular Polygon option.
2. The Parameters dialog box pops up. In the dialog box, enter the number of sides for the regular polygon to be drawn. The number of sides for the regular polygon must be greater than 3. The default number of sides is 5.
3. Move the mouse to the map, and you can see that as the mouse moves, the coordinate values of the mouse position are displayed in real-time in the following parameter box. Enter the coordinate values of the center point of the regular polygon in the box (you can switch between two parameter input boxes by pressing the Tab key), and then press Enter to confirm.
4. Move the mouse again and enter the radius (length) of the circumscribed circle of the regular polygon, and the angle between the radius of the circumscribed circle and the horizontal axis direction (angle) in the following parameter input box, then press Enter to complete the drawing of the regular polygon.

Automatic Surface Construction (Drawing Surface)

The drawing process of automatic surface construction (drawing surface) is as shown in the following figure:

1. In the Features tab, in the Objects group, click the Polygon drop-down button, and select the Automatic Surface Construction (Drawing Surface) option.
2. When the drawn surface intersects with an existing surface object, the enclosed area formed by the surface and the common edge becomes the new surface object.

Automatic Surface Construction (Drawing Line)

The drawing process of automatic surface construction (drawing line) is as shown in the following figure:

1. In the Features tab, in the Objects group, click the Polygon drop-down button, and select the Automatic Surface Construction (Drawing Line) option.
2. When the drawn line intersects an existing region object, the enclosed area of the line and the common side is the new region object. If the enclosed area formed by the drawn line and the existing region object is located within the original region area, it cannot be drawn successfully.