ArcGIS can digitize or trace features without mouse or puck-clicking using several options: streaming, tracing, or freehand drawing. With these methods, the mouse pointer is used to trace the desired feature.
There are three options provided to do this: Digitize by streaming, Digitize by tracing, and Digitize by freehand drawing.
Digitize by streaming (stream mode digitizing)
Stream mode is often used while digitizing hardcopy maps on a digitizing board. Vertices are automatically added at different intervals as the pointer is moved.
Note: To specify the Stream Mode, click the Editor drop-down button > Options. This opens the Editing Options dialog box. In the Stream Mode field of the General tab, specify the Stream Tolerance (how far apart vertices are drawn) and Group (number of points removed from an Undo click) values. Click OK after editing. For the Stream Tolerance, the map units of a data frame are determined by the coordinate system of the data frame. If the coordinate system is Geographic, the map units are in decimal degrees. The Stream Tolerance must be set to a very small number, 0.01 - 0.0001, depending on the map scale, for new vertices to be added when the mouse pointer is moved.
Note: For the Digitize by streaming and Digitize by tracing methods, choosing only the Line, Polygon, or Auto Complete Polygon option from Construction Tools enables the Streaming function or the Trace tool.
Note: Clicking on the map while streaming suspends the streaming session.
Digitize by tracing
Tracing is used to create a new feature which follow the shape of an existing feature. Tracing can be done by tracing directly over an existing feature or at an offset value.
Note: To specify the Trace Options, right-click on the map > Trace Options. This opens the Trace Options dialog box. For the Offset value, the default value is set to zero. This is to trace directly on top of an existing feature. Specify a different value to trace at an offset value. Check the Limit to length checkbox to specify the minimum length of tracing. Specify other settings, and click OK.
Digitize by freehand drawing
Freehand drawing is used to create lines according to the movement of the pointer. The segments created are smooth and are not restricted by any features or boundaries on the map. This option is suitable for drawing quick, free-forming lines on the map.