How To: Importing shapefiles that contain island polygons in ArcCAD
ArcCAD has problems with reading in shapefiles that contain island polygons. These are polygons that have another polygon surrounding them. When labels are assigned, there is more than one label given to the polygon that surrounds the island polygon in the coverage. This causes repeating ids and jumbled attribute data.
Retaining the attribute data associated with shapefiles that contain island polygons while using the SHAPEIN command requires additional steps in ArcView and ArcCAD.
- In ArcView, identify all the island polygon features in the shapefile and select them.
- Once they are selected, create a new shapefile by using the Convert to Shapefile option located under the Theme menu. This produces two shapefiles. One consisting of all the polygon features, and the other consisting of only the island polygon features.
- Using ArcCAD’s SHAPEIN command, convert the shapefiles to ArcCAD coverages and define themes separately giving them easily identifiable titles.
- Use the POLYS and LABELMRK to display the polygons and label points of the theme that contained all the polygon features.
- Use the LABERROR command to display the label errors of the theme. You should see some polygon features that contain multiple label points.
- Identify these features and move the label points of the island polygons outside of their boundary and place them into the area of the surrounding polygon. Use the MODFEAT command to update this feature modification.
- Use the BUILD command to update topology. Display the features again, and use the LABERROR command to verify if your edits were successful.
- Use the UPDATE command to merge the two polygon themes.
The input theme should be the polygon theme that contains all of the features, and the update theme should be the theme that only contains the island polygons. This operation will replace the polygons that lack label points and attribute information with polygons that contain the correct data and labels as they existed in the original shapefile.