As I need polygons, I used ET GeoWizards' Polylines to Polygons tool for this purpose. It worked fine with my smaller dataset of about 9 records, but crashes with my larger dataset of several thousand.
Is there another workaround? You would think ArcGIS 10 would have something as simple as convert polylines to polygons and such, but have not found a suitable tool yet. (Note: buffer not suitable in this case as this is an ellipse not a circle)
Oh, sorry I assumed that you have an arcinfo license when you said ArcGIS 10 without mentioning ArcView. Here is a workaround you can try: 1. Run Minimum Bounding Geometry tool with the default Geometry Type. You will get a rectangle around each ellipse line. 2. Run Buffer with LEFT option to get an "outer" buffer from each ellipse. Use a buffer distance that is larger enough to fully cover the rectangle. 3. Run Union tool to combine the buffers and the rectangles. 4. Run Select By Location tool to select the unioned features by the buffers. 5. Run Delete Features tool to delete the selected features; what's left are the areas inside the buffers that were filled by the rectangles.
Otherwise you would need to write a script to read each ellipse polyline and write it out as polygon.