Snapping in ArcGIS

Summary This topic outlines the snapping capabilities in ArcGIS and explains which capabilities are most appropriate for developers.

In this topic

About snapping in ArcGIS
ArcGIS snapping environment
Editing snapping environment
Comparing the snapping environments

About snapping in ArcGIS

When developing tools in ArcGIS, one of the most common capabilities desired is the ability to precisely define the location of the cursor on the display in relation to another entity (usually a feature) to help complete a given task accurately and efficiently.

ArcGIS has two main alternatives to support snapping: the ArcGIS snapping environment and the editing snapping environment. Each has advantages and disadvantages. Understanding these differences, along with deployment options, will help you decide which alternative is most appropriate for you.

ArcGIS snapping environment

The ArcGIS snapping environment provides the most generic framework for supporting snapping in your customizations. It is available to both Desktop and Engine developers, using the same set of components. This is advantageous when writing a generic tool that might be used in ArcMap as well as in a custom ArcGIS Engine application.

For a detailed discussion on the ArcGIS snapping environment, see Working with the ArcGIS snapping environment.

In general, using the ArcGIS snapping environment is preferred.

Editing snapping environment

The editing snapping environment provides a fine level of control to determine what features can be snapped to, including snapping in x,y, and z. However, the editing snapping environment is only available when you're in an edit session.

The interface you use depends on how your customization will be deployed. For desktop customizations, use ISnapEnvironment in the ESRI.ArcGIS.Editor assembly; for ArcGIS Engine customizations, use IEngineSnapEnvironment in the ESRI.ArcGIS.Controls assembly.

For a detailed discussion on the editing snapping environments, see Working with the editor snap environment or How to work with the snap environment.

Comparing the snapping environments

The following table lists the key aspects of snapping and compares the ArcGIS and editing snapping environments:

	ArcGIS snapping environment	Editing snapping environment
Desktop support	Yes	Yes*
Engine support	Yes	Yes*
Configuration of snapping agents	Yes	Yes
Available outside an edit session	Yes	No
Requires management of cache	No	Yes
Respects definition queries on layers	Yes	No
Supports customization of snap tips	Yes	No
Supports filtering of individual layers	Yes**	Yes
Supports custom snapping types	No	Yes
Access to snap result via the application programming interface (API)	Yes	No

* The editing snapping environment is supported in ArcGIS Desktop and Engine but requires different interfaces for each.

** Individual layer configuration is only supported through the API.