Tiny sliver polygons or gaps between polygons often result from creating new polygons without using snapping or editing shared boundaries without a topology. Slivers and gaps keep your dataset from forming a continuous fabric and should be identified and fixed as appropriate.
There are several general ways you can clean up these errors:
- Use Align To Shape on the Advanced Editing toolbar to adjust features in certain layers to a line you create. Align To Shape works well to update multiple layers when you want some control over the parameters used in the alignment. This includes the shape to align to, which layers are updated, and the tolerance. You can also try some of the other alignment tools available when editing.
- With an ArcGIS for Desktop Standard or ArcGIS for Desktop Advanced license, you can set up a geodatabase topology. Geodatabase topology is the most efficient, automated, and thorough means of finding and fixing these errors. You can apply Must Not Overlap and Must Not Have Gaps rules to find polygons that either overlap each other or have gaps between them. You can also look for Must Be Larger Than Cluster Tolerance errors, which are polygons small enough to collapse during the process of validating the topology.
- You can run the Check Geometry and Repair Geometry tools, which can help find and fix short segments, null geometry, and other problems that could result in sliver polygons.
- You can use the Integrate geoprocessing tool to make polygon edges and vertices coincident. Integrate can help fix both slivers and gaps. However, you need to be careful that you enter the smallest cluster tolerance possible so you don't inappropriately collapse or merge features.
- Use snapping to modify polygon edges and vertices manually using the editing tools. You can also use the Snap geoprocessing tool (requires ArcGIS for Desktop Standard or ArcGIS for Desktop Advanced) in the Editing toolbox.
- You can perform a Select By Attributes query for polygons that have an area smaller than a certain size, depending on your dataset. You can inspect the selected polygons to see if they are slivers, then either use the Editor > Merge command or the Eliminate geoprocessing tool (requires an ArcGIS for Desktop Advanced license) to merge the slivers with neighboring polygons. You could also select each polygon individually and reshape the feature by tracing along the edge of the adjacent larger polygon.