We use coastal vignetting as a cartographic technique to separate littoral zones for deep water areas in many lakes and rivers. This techniques is found on many wall maps and atlases and has been used for years to give maps a more pleasing look. We will look at two different methods to achieve similar goals. One methods uses ArcMap and the other uses Adobe Illustrator.
There are two ways to create coastal vignettes within ArcMap. One involves using just vector data and the other involves creating a raster grid of your waterbody and performing calculations to create the desired effect. In this particular case, we’ll look at using the vector method as we’ll be using Adobe Illustrator instead of ArcMap for the raster exercise.
Step 1: Create or obtain a shapefile of the waterbody you want to use. In this case, we are using Lake of Bays, Ontario. Make sure it is a separate shapefile from other waterbodies.
In this particular lake there are multiple polygon features. These need to be cleaned up before we can proceed.
Step 2: Open ArcMap’s toolbox and select the Dissolve tool in the Data Management>Generalize toolbox in ArcMap. Use the newly created shapefile of the waterbody. This tool will merge all multi-features into only polygon. This is important so when ArcMap needs to calculate the vignetting, it will not use polygon edges running through the interior of the lake.
Step 3: Select the Multiple Buffer tool from the Analysis>Proximity toolbox in ArcMap. Use your dissolved shapefile. Use increments of 5m or 10m depending on the waterbody size. Remember to preface every entry with -5 or -10. In this case we’ve used the following values for the buffers: -5, -10, -15, etc… all the way to -140. The reason for so any values is to all for a smooth colour ramp without distinctive breaks between colours. When your buffers are finished calculating (should take a couple of minutes) then add your newly created buffer shapefile and make sure to sort if by unique values. Then select an appropriate colour ramp (usually a white-to-blue). Remove all outlines and just keep the fill for each class.
With some added trasparency we can further enhance the way this looks to be more smooth. As you can see, this is a very rudimentary usuage of the vignnetting technique. The better method is to use Adobe Illustrator.
In Adobe Illustrator
Adobe Illustrator is a much better choice for coastal vignetting as it provides an easier method and smoother results as you will see. Export your waterbody without outlines (just fill) in an EPS format from ArcMap. In the example below I’ve also exported greyed-out surrounding waterbodies and an outline of the lake.
Step 1: Place waterbody (and any other layers) into an Adobe Illustrator document.
Step 2: Select your waterbody layer and under the Effect Menu select Stylize/Inner Glow. In the settings select the following: Mode- Screen, Opacity- @60%, Blur- 0.4 and make sure Edge is selected. If you have later versions of Illustrator, there is a preview toggle that can be turned on. Keep in mind that the numbers given are very flexible depending on the size or effect you want to give your waterbody.
As you can see, Illustrator provides a much more pleasing effect for coastal vignetting and it also provides much more flexibility than ArcMap. Keep in mind that ArcMap can achieve similar results via using the raster calculator, however the amount of work involved doesn’t really make it a viable option.