Note: You can view this post as a video: Aligning features by tracing.
In my previous post, I used some of the new alignment tools to match edges. Just slightly west of the location I was editing before, I noticed a stream line that should be coincident with the borders of the land-use polygons. Although there are several ways I could adjust the stream, I am going to use the new Align To Shape tool because it allows me precise control when updating shapes. Unlike the other tools I have been using, Align To Shape is located on the Advanced Editing toolbar and does not require a topology.
Align To Shape adjusts all features in the layers I specify to match a shape that I trace. Align To Shape is commonly used to align features that have been captured at different resolutions, scales, or time periods, which cause edges to become braided, overlap, or have gaps between them. In this case, the streams were created at coarser resolution than the land-use polygons.
When I click Align To Shape, a dialog box opens so I can set the adjustment parameters. I first create the shape to align to by tracing the edges of existing adjacent features. Since I want to align the stream layer to the edges of the land-use polygons, there are a few tricks I can use to make sure I trace the correct alignment path. Because the Align To Shape dialog box allows me to interact with the map while it’s open, turning off the Streams layer and displaying only the Land uses layer helps avoid tracing along the stream line. I can also select the polygons and press the CTRL key to limit the alignment shape trace to the edges of selected features only. The ESC key allows me to restart tracing if I make a mistake and need to redraw the alignment shape.
Once I have the alignment shape traced, I choose to adjust the Streams layer and set the alignment tolerance. Any portions of features in the Streams layer that are within the tolerance are aligned to the path I traced. For a layer to be listed, it must be a point, line, or polygon layer that is editable and visible (turned on and not hidden at the current scale because of a visible scale range). The map shows a transparent buffer to represent the current alignment tolerance value, which is given in the data frame coordinate system’s map units. Since the map preview is updated as I change the tolerance, I can immediately see if the alignment appears as I want it. It may take a few attempts to find a tolerance value that aligns features correctly, since initially some of the edges may be outside the tolerance.
Once I am satisfied with the preview, I click Align to perform the adjustment. Now, the stream is coincident with the land-use polygons. Because Align To Shape is an interactive tool that requires manually tracing the shape to align to, it works best for cases such as this one where just portions of features need to be adjusted.
Because I still have the map topology built on these layers, I can select the edges and check that they are coincident using the Shared Features window.