Two Alaskas - Working with Clipping Masks

ArcGIS exports interpolated layers as a multiple panel raster with multiple masks. In order to work with these in Illustrator, we need to unmask and ungroup in a specific way. We also need to introduce our own mask so that interpolated layers can be put next to each other, as shown below. The purpose of this assignment is to practice this procedure by placing two interpolated maps of Alaska in close proximity. Follow these steps:

  1. Open the Alaska.ai file. This file was exported from ArcGIS and shows the result of an interpolation.
  2. Select the map, go to Clipping Mask and select Release. Do this procedure twice.
  3. Select All and Ungroup. Do this three times.
  4. Select the neatline and delete.
  5. Delete panels above and below the map. Only keep panels that include the interpolation for Alaska.
  6. Select All and Copy/Paste. Put the two versions of Alaska next to each other and notice how one map covers the other. To place two maps next to each other, we need to add a Clipping Mask (step 11 below). Delete the second Alaska.
  7. Open the layer palette and create a new layer with the menu that is accessible in the top right of the layer palette. Make sure that this layer is on top.
  8. In this layer, use the Pencil Tool to make a fairly tight polygon around Alaska. Include all islands.This becomes the clipping path.
  9. Select both the clipping path and the objects you want to mask, in this case, Alaska. You can use Select All.
  10. Choose Object > Clipping Mask > Make.
  11. Copy and Paste a second Alaska, and move the two as closely together as you can manage. Add your name.
  12. Create a PNG with the two Alaskas, as below. Link from your index page.
From: Illustrator Help / Clipping Masks