QGIS Compared: Cartography

By Gretchen Peterson

As mentioned in my other posts (visualization), QGIS is easy-to-installintegrates with OpenGeo Suite, and has reliable support offerings, making it a viable alternative to proprietary desktop GIS software such as Esri ArcGIS for Desktop. I’ve written a couple of books on designing cartographic products so it is something I’m passionate about and it is definitely an important component of desktop GIS. So how does QGIS perform when it comes to cartographic design?

In making the examples for this blog post series, I was impressed by the capabilities of QGIS and found it was easy and straightforward to create maps like the Halloween map below.

Halloween Map

Click for larger image

Strength: Text and Image Elements

Placing text and images is as easy as finding the Add new label and Add image buttons on the left-hand side of the print composer (a). Once you add a text box or any other element, the Item properties tab on the right-hand side of the print composer gives you most of the complex options that you’d find in any layout or commercial GIS software such as alignment, display, and rotation (b). You can also align these elements by using the Align selected items button in the main button bar (c).

Placing Text on the map

Click for larger image

Strength: Advanced Techniques

Advanced labeling functionality is included in the main QGIS interface, including SQL-based labeling, font choice, and placement protocols. Exporting a layout to SVG for editing in Inkscape or other design software is easy. Another advanced technique is the creation of atlases, or map books, that replicate a layout for each part of an indexed main map. QGIS provides an atlas composer as part of the core functionality within the Print Composer, a very powerful feature.
 

Strength: Color Blending

An exciting feature is the addition of color blending modes, typically found only in design software, that can add special effects to the look and feel of the map by adding texture or special brightening effects, for example. The following modes are available: lighten, screen, dodge, addition, darken, multiply, burn, overlay, soft light, hard light, difference, and subtract. Color blending can be applied to a single layer in the layer properties dialog (a) or it can be applied to an entire map in the Print Composer (b).

color blending

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Mixed Results: Map Elements

Adding the map to the layout is a little more difficult if you are used to commercial GIS software. You have to use the Add new map button (the wording of which I found to be confusing since it somehow implies a new map rather than the existing map in your project), which adds the map from the main QGIS project to the layout. Another potential area of confusion is the fact that once the map element is added to the project, it doesn’t dynamically update if the main map is changed. In fact, to update it there are actually two buttons in the map element’s Item properties: one to update the preview and the other to set the map extent. The former updates the map if a new map layer has been added or the symbology has changed but only the latter updates the map if it has been panned or zoomed. These, however, are minor quibbles.

Mixed Results: Sizing and Graticules

The Print Composer does have a few shortcomings that I suspect will be cleaned up in later releases. It isn’t possible to change the size of multiple images all at once. For example, enlarging the pumpkin images in the right-hand information panel of the example map has to be done for each pumpkin separately since selecting them all and changing the properties isn’t possible. Also, there is no graticule functionality in thePrint Composer. Instead, the user would need to find or create a graticule line dataset to add as a layer in the map if a graphic-like grid was desired. Another minor quibble is that the size dialog for images has the wrong tab order (if you try to tab between the input boxes the tabbing skips boxes instead of sequentially moving the cursor to the next input box).

Hidden Gem: Gradient Fills

Gradient fills, also known as vignette effects, are also possible, in a new plugin called Shapeburst. You can use it to achieve subtle shading along land-water boundaries but also to do some unexpected things like banding the edges of administrative boundaries in different colors or to reverse-fade the edges of a map. This latter effect takes advantage of QGIS’s built-in inverted polygons tool, which simplifies what used to be a task that would take several steps to achieve.

Conclusion

The cartographic capabilities of QGIS are sufficient to produce almost all the common map layout components with an adequate amount of advanced capabilities and even some options, like the color blending modes, that aren’t typically found elsewhere. Cartography is where many people think that QGIS falls short. However, in making the examples for this blog post series, including the Halloween map, I was blown away by its capabilities. See also the QGIS Map Gallery for more map examples. Overall, my experience with QGIS has been that the visualization, cartography, and editing functions of QGIS have matured to the point where GIS professionals of all types can’t afford not to strongly consider adopting it.

Reprinted with permission from the Boundless Blog.


Published Monday, November 24th, 2014

Written by Gretchen Peterson


Published in

Open Source


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