From GIS to the Desktop – Part 3

By Steven Gordon

In the previous two articles*, we examined the value of taking a map from a GIS to desktop illustration software like Adobe Illustrator, with the goal being map enhancement through an increase in the richness of symbology, color and graphic techniques.

The first article was a brief travel guide; it unfolded an itinerary for getting from a GIS to the desktop while showing the sites you’ll see when your map finally makes landfall in Illustrator. The second article offered a more detailed map for making the trip.

Figure 1. Adobe Illustrator’s graphic capabilities provide you with many ways to enhance the visual quality of your GIS data. (Click for larger image)

In this article we’ll tour Adobe Illustrator’s marketplace of palettes which offer visual wares such as object-level transparency, smooth drop shadows, complex graphic styles, layered symbols, and other visual exotics that you can judiciously shop to dress up the communication value your map.

Windows on the World
We’ll start with the premise that, following the directions in the second article, your map sits comfortably in Illustrator, filled with GIS data or with non-GIS vector artwork exported by your GIS. It should be organized in a hierarchy of layers representing a geographically valid order and respecting the way that Illustrator displays and prints graphic artwork. If you haven’t done so, now is the time to lay out your working tools, Illustrator’s palettes. From the Windows pull-down menu, choose the following palettes to display (they'll be check-marked in the menu if already opened): Appearance, Colors, Layers, Styles, Swatches, Tools, Stroke, Gradient and Type > Character.

Some palettes (Color and Stroke) let you "paint" lines and polygons directly while others (Styles and Symbols) allow you to create master styles or graphic symbols. With master styles or symbols, you can make changes to the master that Illustrator then automatically implements across all data painted with those styles or symbols. The Appearance palette is a powerful laboratory for creating complex symbols and visual effects; it’s like a Layers palette for symbols.

Reduce screen clutter by housing palettes together: drag the tab of one palette and drop it next to the tab of another so that they can be displayed, moved or hidden together. Consider organizing your palettes so that functionally related palettes are housed in different groups. For example, keep Color and Swatches separate so that both may be open at the same time. This lets you drag a new color from the Color to the Swatches palette where it will be readily accessible and editable.

Figure 2. A layout of palettes. (Click for larger image)

Building with Blocks
To build almost anything, we start with building blocks. The foundation for all Illustrator symbols and most visual effects will be laid with a few palettes. Color and stroke are the primary palettes. Stroke refers to the line that is the vector object; the stroke can be a line like a highway or it can be the edge of a polygon like a lake. Color can affect the stroke (a dark blue outline of the lake), the fill (the lighter blue inside of the lake) or both.

Figure 3. Dark blue applied to the stroke and light blue applied to the fill of this lake object. (Click for larger image)

Become familiar with the stroke-fill interface in Illustrator. The Color and Tool palettes have two overlapping color squares. One, a color-filled rectangle, represents fill while the other represents stroke. The one that appears on top of the other in the palette is the one selected for editing when you change colors.

Where do you get colors? You can create your own using the color sliders in the Color palette, perhaps using a CMYK print guide to help you compose a set of colors that will print as you intend. You can also find palettes of colors, constructed by Adobe, by selecting Window > Swatch Libraries. For you do-it-yourself-ers, build and save your own customized library of colors which you can use with other maps. For example, working on a map with a Southwestern U.S. theme, create desert colors (or use the Eyedropper tool to sample colors from nature or art images opened in Illustrator); drag the colors from the Color palette to the Swatches palette; and then from the Swatches palette menu, save the palette so that it’s accessible from Window > Swatch Libraries when working on subsequent maps.

Figure 4. Example of a Southwestern palette sampled from artists' work, photographs, paint store chips, and experiments using the Color palette. (Click for larger image)

By editing a swatch, you can turn it into a "global" color. Being global, any changes you make later to the composition of its color (adding magenta and removing cyan, for example) will be reflected automatically in all objects painted with that swatch.

Another kind of color fill is the gradient. It comes in linear or radial flavors. Consider using a gradient to fill a legend box or an inset area on the map. Gradients are "live." You can change the shape of the object filled with the gradient and the gradient automatically refills the new shape.

Gradient Mesh is a powerful visual effect. Graphic artists model complex shapes with mesh (examples of photo-realism created entirely as vector artwork in Illustrator here). Mesh is an easy tool to use if your needs are modest. Large areas of solid color can be changed into a softly airbrushed, variably colored shape using mesh. To do this, select your area, then, with the Gradient Mesh tool, click at different spots within the shape. Keep it simple with a few well-spaced points. When you change the color of a mesh point, gradients of color will flow from that point but will be stopped by the color of the nearest neighboring mesh point. To change a point, click with the Gradient Mesh tool on any point inside or along the border of the shape and then click on a color in the Swatches palette. Use the Gradient Mesh tool to drag points around or modify the shape of the mesh lines connecting the points (which changes the shape of the gradient flowing from points along the line).

Figure 5. Mesh used as a background for this city map of Honolulu. (Click for larger image)

Appearance is Everything
Bare lines and polygons, painted from a limited palette of garish colors, may be all that is offered by your GIS, but with Illustrator you can achieve much more. The Appearance palette is the place for crafting sophisticated symbology for lines and polygons. One of Illustrator’s most subtle traits is that it can target objects, groups of objects and whole layers as recipients of visual effects. And knowing how Illustrator does this will be key in successfully applying Appearance palette effects as you intend.

For our purposes, let’s begin with a single symbol: a multi-line interstate symbol. Select an interstate line on the map and give it a green stroke. In the Appearance palette select the green stroke and then click on the Duplicate Selected Item icon at the bottom of the palette. With this new stroke selected in the palette, give it a new color and a thinner stroke. Repeat this process, picking a different color for the third stroke. Now your interstate line appears composed of multiple paths.

Figure 6. The interstate symbol constructed in the Appearance palette. (Click for larger image)

Turn your new creation into a style you can apply to the rest of the interstates. First, make sure the Styles palette is open. Then, with the interstate line selected, drag the graphic thumbnail from the top-left of the Appearance palette and drop it in the Styles palette. Viola! You have a complex symbol that you can recycle on other lines. Note that later you can edit this style by selecting it in the Styles palette and then changing its composition in the Appearance palette--anything painted with this style will automatically change to the new appearance.

Figure 7. A list of readymade styles available from the Styles palette. (Click for larger image)

Some complex symbols, like the interstate, will not intersect in a pleasing manner. The casing lines of one interstate will cross those of another interstate. To make all interstate casing lines intersect cleanly, select all interstates, group them, and then paint the group by applying the interstate style you created to the entire group.

Double-line borders, often used in older maps, are easy to produce and apply to polygons like map neatlines, inset areas, parks, and political boundaries. Once again, you’ll work in the Appearance palette. First, select an object and give it thick colored stroke. Duplicate the stroke in the Appearance palette and make the duplicate thinner and lighter or darker than the original stroke. Next, select the original thicker stroke in the palette and from the Effect > Path > Offset Path menu command, enter a negative offset value in the Offset Path dialog box. Click the dialog’s Preview button so that you modulate the value until it yields the look you want.

Figure 8. A double-line border symbol constructed in the Appearance palette. (Click for larger image)

Anything you create in the Appearance palette is "live:" you can select an object or style painted with something you created in the palette and change any of the elements composing that appearance. For example, you can edit the amount of offset of the thicker border in the double-line border by double-clicking the Offset Path line in the Appearance palette and entering a different value in the Offset Path dialog box that pops up.

Special Effects
The dynamism of the Appearance palette will also prove useful when you experiment with commands selected from the Effect menu.

Note that some of the same command names appear in the Filter menu; they are different, however. The Filter commands are not editable later. Once you use a Filter, you must use Undo to change it. Effects, by contrast, can be changed at any time by recalling the command’s dialog box from the Appearance palette, as discussed above for the Offset Path effect.

Before using any of the Effects that have a raster component, such as the Drop Shadow and Glows, be sure to set the resolution of these effects by editing the Effect > Document Raster Effects Settings. This avoids the printing of your smooth shadows at the default value, a visually coarse 72 dpi.

Figure 9. The Document Raster Effects Settings dialog. (Click for larger image)

Drop Shadows are a popular technique for calling attention to symbols. Effects can be applied to individual objects, groups of objects or to entire layers. What’s the advantage of applying them to layers? When a drop shadow (or other effect) is applied to a layer, anything you create on that layer - or paste or move to that layer - has the drop shadow applied to it automatically. The drop shadows on everything on the layer can be controlled by editing a single dialog accessed from the Appearance palette. To create a drop shadow, select an object, group or layer (for the layer, click the circle icon at the right of its layer name in the Layers palette) and then select Effect > Stylize > Drop Shadow.

Figure 10. The Drop Shadow effect dialog and example of its use. (Click for larger image)

Closely related to the drop shadow is the Effect > Stylize > Inner Glow. Use this effect to add a vignette to a large water body or a soft gradient inner border to an area like a country or state. If you change the shape of the object, the vignette adjusts automatically to change.

Transparency lends itself well to mapmaking because with it you can change the color or tone of map artwork that lies below objects whose transparency you change. If you place a terrain image in Illustrator underneath layers that contain political boundaries, then you can select a boundary object--a county, for example--and make it darken the terrain image underneath it.

Use this technique, also, to colorize parts of a terrain. If you have objects representing different classes of land ownership, select the objects of one class, fill them with a unique color, and then in the Transparency palette change the blending mode from the default Normal to Hue. This changes the hue of the artwork below the objects. Repeat with objects representing the other classes of ownership.

Figure 11. Transparency and color applied to objects that affect an underlying terrain image. (Click for larger image)

You can apply transparency to objects, groups or layers.

Symbolism over Substance
So far, we’ve discussed methods of symbolizing lines and areas. What about point symbols?

Illustrator provides a rich environment for designing symbols and distributing and editing them in maps. When discussing symbols, there are two terms at play here: one is map symbol (tents for campsites, airplanes for airports) and the other is Illustrator symbol. The latter refers to graphics, from simple squares to sophisticated 3D objects and imported images that you turn into "symbols" and use as symbol "instances" when placing them on a map. The Symbols palette is the library that transforms objects into symbols and stores them for use as instances.

Figure 12. The Symbols palette loaded with map symbols, each of which is an Illustrator symbol. (Click for larger image)

To use Illustrator’s symbols, first be sure that the Symbols palette is open. Then create or select some artwork - an object, a group or an image you imported into Illustrator - and drag it into the Symbols palette. Your artwork is now a symbol. You can now drag the symbol out of the library and move it into position on the map. That symbol is actually an instance of the symbol that’s stored in the Symbols palette.

If you’ve populated a map with symbol instances, you can change them all at once by editing the master symbol in the Symbols palette. To do this, drag another instance out of the palette, select Object > Expand and click OK. Modify the artwork and then select it, drag it back into the Symbol palette while holding down the Option (Macintosh) or Alt (Windows) key to drop it on the original symbol. All instances of that symbol automatically change to reflect your edits to the master.

Also, you can change your mind about how you symbolize point features and connect another symbol with all of the symbol instances you placed on the map. Simply select all of the instances, then select another symbol in the palette, and from the palette menu select Replace Symbol.

Illustrator ships with a set of about 30 map symbols you can access from Windows > Symbol Libraries > Maps. If you want to access over 1,500 high-quality, royalty-free symbols, many of which are applicable to mapmaking, go here, register and then download the symbol libraries.

Once you begin making or acquiring symbols, you can make your own preset library that will be accessible from Illustrator’s Window > Symbol Libraries list. From the Symbols palette’s menu, choose Save Symbol Library and in the Save Palette as Symbol Library dialog box, name the library and click Save. The library will be saved inside Illustrator’s Presents > Symbols folder.

Not all symbols are created equal - some are 3D and considered superior to flat, boring 2D symbols. With little effort, you can turn a mundane camping symbol into a 3D tent viewed in perspective. Take any object and select Effect > 3D > Extrude & Bevel, click Preview in the 3D Extrude & Bevel Options dialog, and then begin experimenting with the Position and Extrude & Bevel controls. You may need to click the More Options button so that you can change the lighting conditions, which will help you control the light, shadow and color of the 3D object you’re creating.

Figure 13. A sequence of art showing the evolution of 2D artwork into 3D symbol. (Click for larger image)

Your 3D map symbol is "live," which means that at any time you can select it, double-click the 3D Extrude & Bevel line in the Appearance palette to return to the 3D Extrude & Bevel Options dialog so that you can change the rotation, extrusion or other 3D parameter.

If you are satisfied with the overall appearance of the 3D symbol but want to tweak its colors, you may have to expand the symbol (Object > Expand) and edit its artwork. Once you do this, though, your symbol has lost its link back to the 3D effect - instead it is flat artwork that looks 3D.

You're Not My Type
There is no reason that type should be excluded from all the fun. Map lettering and labels can have many of the same live visual effects applied to them as other artwork. A common visual effect is to outline lettering so that it contrasts properly with the map behind it. Another use of Illustrator's visual effects is to give font characters a hand-rendered appearance. This kind of effect makes use of Illustrator's Brushes palette along with some of the effects discussed above.

Figure 14. Label with red stroke behind white fill. (Click for larger image)

Figure 15. Title type with characters painted with a Brush and multiple fills with Effects. (Click for larger image)

Take a Free Trip
Desktop software makes innovative visual expression a rewarding experience, for the mapmaker as well as for those who will use that map.

You can download a tryout version of Adobe Illustrator.

You can also download a demo version of the Avenza MAPublisher filters.

For more detailed discussion of some of the visual effects covered in this article, read selected excerpts from the Adobe Illustrator CS Wow! Book (Peachpit Press).

From GIS to the Desktop (March 1, 2005)

From GIS to the Desktop - How Do You Get There From Here? (Aug. 11, 2005)

Published Friday, February 17th, 2006

Written by Steven Gordon

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