Merging - Combining Like Type Shapefiles
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Concept:
This technical skills lesson will demonstrate how to merge shapefiles together (two or more) to form a single shapefile. The shapefiles ideally should be contiguous for the best results and be in the same projection, but this is not required. The shapefiles must be of the same type, such as lines with other line files, different types of files such as a polygon with a point file cannot be merged. The data within the shapefile must be of the same type, for example, a census tract file and a county boundary file cannot be merged. When the merge is completed a new shapefile will be created, use an appropriate naming convention and storage location. Merge and tabular join are not the same operation. One of the reasons to merge shapefiles is so that a regional geography can be defined. A regional geography could be a metropolitan area or the service area of a college. For example, when a comparison of income levels is performed at the individual county level, each county has a unique classification. For the regional geography there is only a single classification. Another example might be a population growth study of two adjoining counties at the census tract level. The same color ramp for population should be used, but this would require manually setting the break points. If the two counties were merged together then only one color ramp would be produced for the counties. Another reason to merge multiple shapefiles together is so that they are easier to work with as a region. For a typical study there might be numerous maps created, merging simplifies the process, making for an easier analysis. Instead of working with multiple counties, for example, only a single file for the entire region is required. Point, line and polygon files can all be merged. The individual shapefiles should have the same attributes and must be of the same format. With some of the changes in how U.S. Census data is now downloaded it makes better usage of time to merge the shapefiles together before doing a tabular join.
Prerequisites:
The ability to load shapefiles/layer files in ArcMap and have experience with symbology.