Snapping allows you to create features that connect to each other so your edits are more accurate, with fewer errors. When snapping is turned on, your pointer will jump, or snap to, edges, vertices, and other geometric elements when your pointer is near them and within a certain tolerance. This enables you to position a feature easily in relation to the locations of other features.
All the settings you need to work with snapping are located on the Snapping toolbar. Snapping is not limited to being used while editing, as it is utilized in other areas of ArcGIS, such as georeferencing and the Measure tool on the Tools toolbar. By default, snapping is enabled, and the active snapping types are points, endpoints, vertices, and edges. You can turn on or off individual types from the Snapping toolbar. To turn off snapping completely, click the Snapping menu and remove the check mark next to Use Snapping.
When snapping is enabled, the pointer icon changes as you move around and pause on various features on your map. Each snapping type (vertex, edge, endpoint, intersection, and so on) has its own feedback, which matches the icons on the Snapping toolbar. For example, the cursor is a square when you are snapping to a vertex and becomes a box with diagonal lines when you are snapping to an edge. By noting the cursor appearance and the SnapTip text that pops up, you can immediately determine the layer you are snapping to and which snapping type is in use.
To help you distinguish the icons on the Snapping toolbar, rest your pointer on a button; note that a piece of text pops up (a ToolTip) near your pointer with the name of the button, and a description appears in the status bar at the bottom of the application. In addition, you can change the appearance of the buttons on the toolbar so the icons display with their names or the buttons display as text-only without any icons. To do this, click the Customize menu and click Customize Mode. While the Customize dialog box is displayed, right-click an icon on the Snapping toolbar and click either Text Only, Image Only (the default), or Text and Image. This tip applies to any toolbar in ArcGIS.
Snapping while editing
Snapping is useful with many editing operations, such as creating polygons that do not overlap or have gaps between them, drawing lines that connect to each other, or placing a point exactly along an existing line. For example, suppose you are creating a new segment of an electric line that begins from an existing transformer; you want to ensure that the vertex of the line connects precisely to the transformer. Snapping makes this type of task accurate, quick, and easy. You can snap to any feature layer in your map, not just ones you are currently editing. This allows you to snap to features in a computer-aided design (CAD) drawing, coverage, feature class from another geodatabase, and so on.
Snapping can also be used to move a feature to an exact location in relation to another feature. For example, you can move a parcel and have one of its corners jump, or snap, precisely to a corner of another parcel. Simply move the parcel's selection anchor to its corner vertex after setting the appropriate snapping properties. Then move the parcel to its new location until the selection anchor snaps to the corner vertex of the other parcel.
If you have multiple snap types active, the sequence in which the snapping occurs is determined automatically. The highest priority is given to snapping to sketch elements.
Choosing the snapping environment to use for editing
When you are editing, there are two snapping environments available to you. The default environment uses the Snapping toolbar, but you can instead choose to use the editing classic snapping environment. With classic snapping, you can set up snapping on a layer-by-layer basis.
The editing classic snapping environment refers to the snapping functionality that was available during an edit session in ArcGIS 9 and earlier using the Snapping Environment window. In classic snapping, snapping settings are specified by choosing a layer and snapping type (vertex, edge, or end) in the Snapping Environment window. This snapping functionality is off by default and has been replaced with the Snapping toolbar, which provides a flexible, easy-to-use snapping environment with more snapping types, more options, and better feedback than classic snapping. Since there may be some scenarios where you need to access the classic snapping environment, such as when performing raster snapping with the ArcScan for ArcGIS extension, you have the option to switch to classic snapping.
You enable editing classic snapping on the Editing Options dialog box and use the Snapping Environment window to turn on snapping for individual layers and snap types.
While classic snapping is enabled, editing tools only use the classic snapping environment. However, georeferencing tools, the Measure tool, and other non-editing tools continue to use the snap settings on the Snapping toolbar.