GIS Skill Builder: Merging Multiple ThemesCombining multiple themes into a single theme in ArcGIS 9.0.Before embarking on this task, you’ll want to do a little pre-planning. In ArcGIS 9.0, you’ll use an Append function to combine multiple themes (shapefiles, feature classes, etc.) into a single file.* Because you are appending data to an existing file, you will need to designate which are your input themes and which is your output theme. Your input themes may contain any data, as long as they share the same geometry type as your output theme –- in other words, you can only append points to a point theme, lines to a line theme, and polygons to a polygon theme. You cannot, for example, combine points and polygons into a single theme. (You may, however, create a single geodatabase that contains point, line, and polygon feature classes as well as tables, images, etc.) If you seek to combine several themes that differ only in their spatial extents, such as census tracts for different counties, the choice of input and output themes may be arbitrary. If, however, you wish to combine themes with different attributes, keep in mind that your choice of output theme will dictate the attribute fields you’ll have in your results. Any attributes in an input theme that don’t exist in the output theme will be removed during the append process. You may have to spend a few minutes creating or adding fields to your output theme in ArcCatalog before you append to ensure that you retain all the attributes you need. *If you have ArcView 3.x or ArcGIS 8.x, you may prefer the Geoprocessing Wizard’s "Merge Themes" tool to combine data. In ArcGIS 9.0, it has been replaced by the Append function described below. For those interested in more information on this topic, a threaded user discussion, with links to additional resources, is available at: http://forums.esri.com/Thread.asp?c=93&f=983&t=129867#381707
Below are two procedures for accessing and applying the ArcGIS Append function:
ArcCatalog Method:1. Launch ArcCatalog. 2. Access the list of ArcToolbox functions by pressing the 3. In the ArcToolbox list, navigate to and double-click the Append tool, found here: Data Management Tools > General > Append 4. Drag-and-drop (or 5. Drag-and-drop (or 6. In the Schema Type field, choose “TEST” if you want to ensure that files will only be combined if they have the same attribute fields. In this case, the destination theme will receive all features from the input themes as well as their attributes values. If your input data have different attributes than your output data, you will need to choose “NO TEST” to complete the append function. 7. Press OK. 8. If appropriate, go to File > Rename (or right-click on the theme in the left-side folder list and select Rename) and type in a new name for the file. ArcMap Method:1. Launch ArcMap. 2. Press the Add Data button
3. Access the list of ArcToolbox functions by pressing the
4. In the ArcToolbox list, navigate to and double-click the Append tool, found here: Data Management Tools > General > Append
5. Drag-and-drop (or
6. Drag-and-drop (or
7. In the Schema Type field, choose “TEST” if you want to ensure that files will only be combined if they have the same attribute fields. In this case, the destination theme will receive all features from the input themes as well as their attributes values. If your input data have different attributes than your output data, you will need to choose “NO TEST” to complete the append function. *Reminder* If you are combining data with different attributes and want to maintain all original attributes in the output file, you must
first create an output file that contains all incoming field names before using the Append tool.
8. Press OK. 9. In ArcMap, if your output data is already loaded, refresh the view to see the new features it contains. If it is not loaded, add it to verify success.
10. Your output data may need to be renamed to reflect its new content. If so, close your ArcMap session and open ArcCatalog. You will not be able to rename data that is open in ArcMap. 11. Navigate to and select the output theme.
12. Go to File > Rename (or right-click on the theme in the left-side folder list and select Rename) and type in a new name for the file.
13. Check your work by opening a new ArcMap session and loading the renamed data.
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button or using the Window > Arc Toolbox pulldown menu. 
browse to) one or more input themes from ArcMap into the Input Features list. 
browse to) your output theme in the Output Features text box. 
or use the File > Add Da ta pulldown menu to load the data you wish to combine. 
button or using the Window > Arc Toolbox pulldown menu. 
browse to) one or more input themes from ArcMap into the Input Features list.
browse to) your output theme in the Output Features text box. 
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