Update 3 5 control boundary

3-5-control-boundary.md

 # Controlling regional boundaries (and how to use Area Pane)
 
+![](img/3-5-area-pane.png)
+
+The **Area Pane** shows the map area or cross-section position of the selected layers. 
+
+*  For *Horizontal Plane* and *Vector Plane* layers, the map area is shown as a rectangle.
+*  For *Vertical Cross-Section* and *Vector Cross-Section* layers, the cross-section position is shown in a line.
+
+The **Area Pane** shows the whole map, by default. You can control the regional boundary of the map area or the cross-section position as follows.
+
+### Zooming in/out or moving the map area
+
+*  You can enlarge or reduce the map area by clicking the **-** or **+** icons at the bottom of the **Area Pane**. 
+
+*  You can move the map area by clicking the **<**, **>**, **^**, **v** icons.
+
+You can also scroll or drag your mouse to zoom in/out or move the map area.
+
+### Changing the layer position/area
+
+When the mouse cursor is placed on the border line map in the **Area Pane**, it displays the longitude/latitude of the cursor position in the top-right of the **Area Pane**. It also displays the start and end points of the map area or cross-section position as green dots.
+
+You can change the map area or the cross-section position by place the mouse on the green dots (start and end points) of the rectangle or the cross-section position, and drag the points to the desired positions.
+
+
 
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