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Snapcodes

Sometimes you may want to select graphics by an exact position, such as the end of a LineString item, or you may want to draw to an exact location, such as the centre of a circle.

By using snaps you can draw to precise points on existing graphics, such as ends of LineString items, midpoints of LineString items, centres of circles, etc.

Some snapcodes such as Line and Area appear at the cursor position when your cursor is in the correct location. By clicking when you see these snapcodes, you know you are snapping to the LineString or Polygon item.

The available snaps, with their keyboard initial letter (‘hot’ key) shortcut, are shown in the table below.

Some are used only for selecting graphics, not in situations where you are creating graphics:

Area	Snap to the centre point of a Polygon item. In the situation where several area items are found, the Polygon with the smallest extent is selected unless the Select dialog is in automatic mode, (automatic mode is set in the User Interface and Commands tab of the Options dialog) when Automatically show Select Item dialog is ticked, the Select Item dialog shows whenever you click on the map window, if there is a choice of items to select. When used with TINs and DTMs, it snaps to the Z height of the 3D item.
Box	Snap to the justification point of a BoxText item.
Centre	Snap to the centre of an arc or circle, or to the centroid of a Polygon item.
Dot	Prevent snapping. The exact position of the cursor is used.
End	Snap to the nearest end of a LineString item.
Find	Finds all of the features under the click location and displays all possible hittable items in the Select Item dialog:

Grid	Snap to the nearest snap grid intersection point. This snapcode is available only if the snap grid is displayed and enabled for snapping. See Snap Grid [CAD-Snapping].
Hook	An item’s hook point is the centre of a rectangular box drawn around it. It does not work with all item classes, for instance, not with point items.
Line	Snap to the nearest geometric point on the nearest LineString item.
Middle	Snap to the mid-point of a LineString item segment.
Normal	Snap to the nearest LineString item, correcting to perpendicular.
Point	Snap to a Point or Point Text item.
Query	Show the MapTips™ for that point.
Raster	Snap to a raster pixel. This snapcode is not available on Image items. This is the only snapcode which cannot be typed from the keyboard.
Select	Choose from overlapping graphics. When you are using Select [Home-Selection], this snap allows you to choose which item you require in ambiguous snapping situations. The Select Item dialog opens:
Vertex	Snap to the nearest end of a LineString item, joint of a MultiLineString item, vertex point on a circle, etc.
X-Cross	Snap to the nearest intersection of two LineString items.

If the cursor is near enough to the relevant item then you will see the snapcode name displayed on the cursor. You can then simply press the left mouse button to enter that snapcode.

Alternatively you can press the initial letter of a snapcode on the keyboard. In this case SIS will look for the closest item which matches that snap code. Note that you cannot type R for the raster snapcode because this conflicts with Relative positions used by the Position Bar.

To prevent the cursor snapping to a point, press the D key and the exact position of the cursor is used, with no correction.

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