Trim Surface is used to define the boundary of the surface loaded in the  Surface Data form to remove information that is not necessary by the design. I.e. if a large LIDAR tile has been simply loaded and it only requires a certain part of it.

Draw a polygon

The Drawing Mode tool  should be selected with no polygon drawn on the surface, then the drawing cursor  will appear when entering on the plan.

• Draw a rectangle: left-click on the plan, hold down and band select the area. Release the mouse when finished.
• Draw a polygon: left-click on the plan to add the first point, then click as many time as you want to add points. Finish the polygon by right-clicking the mouse. During the drawing, you can press the 'Back' key to delete the last vertex, you can also cancel the drawing by pressing the 'Esc' key.

Edit the polygon

The Drawing Mode tool   should be selected to edit the polygon.

Handle the plan

• Zoom in/zoom out by rolling the wheel of the mouse.
• Band zoom an area by selecting the Band Zoom tool , then the band zoom cursor   will appear when entering on the plan.
• Zoom to full size extents with the Extents tool  .
• Drag the plan by holding down the wheel of the mouse and move it.
  
  

Trim the surface

After drawing the polygon, the surface is automatically trimmed by clicking OK, then the updated data is displayed in Surface Data.

The surface will not be trimmed if the polygon has crossing edges.