Cartographer's Toolkit

Map Making Tips, Tricks, and Inspiration

Map Generalization

September 22nd, 2011

Feature generalization is a key cartographic concept missing from many GISer’s skillsets. There are quite a few ways to generalize a feature layer*, but the big one that tends to get overlooked by the GIS crowd is line smoothing. For example, a detailed county boundary dataset is great when you are mapping just a few counties but if you are mapping the entire U.S., you want to have fewer vertices, especially around the shorelines, where the line can get quite complicated. If the scale is the entire U.S. those shorelines do not need to be representing every single bay and inlet as if it were a local boating map.

To smooth lines in ArcMap you have to have the ArcEditor license or above. You use the Advanced Editing toolbar, generalization tool after making sure the data are in an edit session (via the editor toolbar). If you’re in Illustrator, there’s always the smooth tool and the path > simplify tool. Or you can just find another dataset that’s already smoothed (for example, detailed counties versus general counties). If you are using ArcView (now called ArcGIS for desktop basic) you can get ET Geowizards and use the smooth polylines or smooth polygons operations.

The basic idea is that while we GIS professionals are very much interested in maintaining the integrity of our data, this often is to our detriment when we try to create cartographic quality maps out of data that’s meant more for analysis than for information display.

*Other ways include: merging features, changing data (from counties to continents as you zoom out to a world-wide scale, for example), and removing labels.

Cartographer's Toolkit

Map Making Tips, Tricks, and Inspiration