territory
Many people think of a territory as a spatial container, something with an interior and a boundary. On maps, things like countries, states, parks, and private properties are generally bounded spaces. Similarly, geographic datasets often use polygon geometries to represent these kinds of geographic things.
For cartographers, the container metaphor and geometry of territories both pose a number of recurring problems that affect the legibility and spatial association of map elements. The patterns below describe common solutions to these problems.
morse code border
Use a dash-dot pecking system with variations to distinguish ierarchical political borders (countries, states, counties, etc) that overlap other features (like rivers).
Political boundaries and cadastre (property) lines often have both an origin and an originating story.
For origin stories, these lines generally reflect one of three sources: (1) those that follow natural boundaries, like a river and mountain range, (2) those that originated on a map and were carved up arbitrarily, (3) those that originated through ground survey and may follow arbitrary straight lines that at times may be tied to natural landmarks on the ground (as do many early pitches in New England).
For originating stories, these lines often generate landscape patterns that become visible in the landcover visible from air photographs and satellites. For example, the shelterbelts, hedgerows, ditches, and two tracks of agricultural landscapes often reflect political and parcel lines, as do the grids of road networks in colonial and imperial landscapes.
As a result, political and parcel lines often overlap other lines on a map. For the cartographer, the recurring problem is to find a solution that allows the reader to see where the political or parcel line follows a natural boundary and when it follows a more abritrary path.
Many cartographers solve this with a system of pecked lines, variations of dash-gap-dot-gap, that allow the reader to see where the political or property line overlaps an underlying line, like a river. In this solution, the cartographer places the line with the Morse code over the river line. There are other solutions to the problem that do not employ pecking systems. For example, some cartographers draw the political or parcel stroke with a lighter value and greater weight and place this under the river line. The latter solution may work best when the cartographer does not need to develop a hierarchy of boundary lines for a theme (e.g. signal national vs. state vs. county).
banded border
Use an inner stroke with relatively wide weight to signify a territory’s border and offset one or more paths with lighter strokes of the same hue towards the interior.
The central problem is the need to signify different territorial regions without diminishing the legibility of the features and labels within the territories. Using some sort of area fill for the territory will often reduce the legibility of interior features and labels.
To solve this problem, you will often see cartographers reduce the strength of a territory’s fill in the interior and increase visual emphasize near the border.
National Geographic cartographers have long used a banded border pattern. It consists of a relatively wide line on the inside of a border with one or two additional lines of the same width but reduced value and/or saturation that are offset from the first line to form a short sequence of graded bands.
A glowing boundary is another solution to the same problem. In the past, cartographers would use a brush and wash to gradually increase the strength of the border color near the boundary without creating stepped bands. In Adobe Illustrator, you can generate this effect with an inner glow.
neutral coastlines
Place political and parcel boundary lines on top of coastlines for exceptional cases, not by default.
Political and property lines generally enclose a region on a map, but coastal boundaries tend to be ill-defined. Territorial boundaries often extend offshore, while property lines may shift over the day with tides.
For this reason, a cartographer should try to signal discrepencies between the water’s edge and the territory. Often, the solution is to cut and remove the political or property line where it follows the coast. Usually, this solution is paired with Morse code border and border band patterns; the former will break at the shoreline and the latter will continue along it. This creates the illusion of a territorial container while signaling the ill-defined coastal boundary As a result, such maps tend to recognize the terrestrial territory and conceal the maritime boundary.
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