|The Caribbean Sea map by David Barnes (2006) illustrating these effects:|
Denis Wood (1992; 153) termed the mountain symbols that depict physiographic features "hillsigns". These symbols were applied to point GIS data with an attribute that was added to distinguish the different types of landforms. Physiographic features were classed into fourteen categories based on their names, but other classification methods could be used. Each feature type was assigned a slightly different hillsign. Some features were assigned symbols composed of groups of hillsigns; these were used for such physiographic features as mountain ranges and ridges.
Coastal rakes were used as an alternative to the more commonly seen coastal vignettes that use graded colors. In either case, one advantage is that while historical maps had to be laboriously etched or engraved and then painted, all by hand, these methods can be replicated quickly and easily with GIS. Both effects can be achieved using either constant or variable width buffers; the difference lies in how the buffers are symbolized. The coastal rake effect is achieved by symbolizing the buffers with fill patterns that are composed of a set of dashed lines with different irregular spacing for the dashes.
The figure below illustrates variation in one of the line symbols that were created for the Caribbean Sea map. A variety of fill patterns were created for the various buffers on the Caribbean Sea map, with near-shore fills composed of more closely spaced dashes.
For the rhumb lines, the north arrows were used to digitize lines as GIS features connecting points of equal bearing. Because the lines are GIS features, they can be placed under the land masses, helping to promote figure-ground.
On this map, there is also decorative ocean art, including ships and sea serpents (Figure 6). These are created as marker symbols that can be placed in a focused data frame. In other words, the point symbols added to the map as graphics that are spatially referenced to the geographic data.
The symbols for the ocean art were created as drawings that were saved as image files in Enhanced Metafile or .emf format. In the GIS, marker symbols were created as picture marker symbols based on the .emf files.
The first time period examined was the late 1500s to early 1600s. A Caribbean Sea map was created to develop and demonstrate some of the mapping techniques found on maps that were examined from this time period. On the Caribbean Sea map (above), there are a number of cartographic effects drawn from historical maps, including the following.