Raster tracing is useful when you need to have more control over the vectorization process or need to vectorize a small portion of an image.
ArcScan for ArcGIS supports the ability to snap to raster cells. Raster snapping allows you to accurately create features by snapping to raster centerlines, intersections, corners, ends, and solids.
Raster tracing is useful in cases in which you need to have more control over the vectorization process or need to vectorize a small portion of an image. Raster tracing allows you to manually trace raster cells and generate vector features.
Using the tracing tool, you simply point the cursor in the direction you wish to vectorize and click. With each click, features will be generated at the centerline of the raster cells. The current vectorization settings influence the output vector geometry. You have the option through the Editor toolbar to generate line and/or polygon features.
Automatic and interactive vectorization both require settings that influence how the output vector features are generated. These settings, also known as styles, can be saved and reused with raster images that possess similar characteristics.