The symbols and legend included on a finished map are details carefully chosen by the map's designer- they convey the primary meaning of the map, and, if they are unclear in any manner, can arguably obscure the map's intended purpose. In the case of symbols rendered proportional to the relative size or magnitude of the thematic feature, it is imperative to choose colors and shapes that maximize the viewer's understanding of the phenomena being displayed on the map.
The above thematic map intends to convey the net increase and decrease in jobs for each state in the U.S. for the period between 2007 and 2015. The circle sizes are proportionate to the magnitude of net loss/gain, and the color indicates whether the number of jobs represents an increase or decrease. The legend, in the lower left corner, uses hollow circles to represent the relative numbers, as it applies to both the increase and decrease amounts, and indicates the colors red and green represent the net loss and gain. The increase and decrease amount circles on the map are two feature classes, created by querying and exporting both sets of values from an original layer that contained both positive and negative values in its attribute table. This was accomplished by adding a field to the feature class containing negative values, and calculating the absolute values of those numbers, as the layer symbology, as a display of proportional symbols, does not support the use of negative values. Thus, each layer- one representing net increase, and the other net decrease- is symbolized separately, but with the same symbol range, which allows each set of values, both negative and positive, to be symbolized in differently colored circles.
Color, inasmuch as it is used as a cartographic tool, is probably taken for granted by most map viewers- another map element unremarkable the vast majority of the time, except when it is used poorly, and then becomes unmissable. The color palette chosen by the map maker isn't purely an aesthetic decision either, it is carefully considered, so that the feature being displayed appears in a logical context. A map with purple water features and blue forest tracts wouldn't be considered seriously by most, save as a piece of art. Color is also of utmost importance within the context of the choropleth map, which displays some feature, grouped into classed categories, based upon some measurement. Color variation for different classes is often seen as a change in saturation or lightness, within the same general hue.
Above is a linear color ramp- the darkest and lightest shades vary by a certain amount for the R, G and B values, and the classes/shades between are a linear progression of those values, yet the color remains a constant hue.
The light/dark progression of one hue is, however, augmented, as in the ramp above, by adjusting the amount of the interval between the R, G and B values between the darkest colors. The object here, were these colors being used in a choropleth map, would be to retain the same hue for all of the classes, while appreciably varying the lightness and saturation, so that whatever is being symbolized on the map is shaded in colors different enough to tell one apart from the other, based on the value of the hue.
Finally, we have a color ramp produced by Colorbrewer.org, which is an exceedingly useful tool for generating color ramps such as these. The above ramp uses a slightly different hue for the top, darkest class, and then varies the lightness of the pinker hue in the classes below. The use of this type of ramp would be invaluable in a map with which one might want to display different areas in different shades, to indicate the amount of some measurable thing- the colors are all in approximately the same hue, and yet vary enough from one another such that one area would be visually distinct from another.
Of the many small details essential for a well-made map, labels rank among the most likely to be overlooked. They are a small element that, when done well, warrant no particular notice, but, when executed poorly, have real potential to destroy a map's aesthetic beauty and practical use. A working knowledge of typography basics is an integral skill in creating functional and visually appealing map labels.
Mapping the City of San Francisco presents a perfect opportunity for practicing skills and various techniques in effective map labeling, and the above map is my submission. What would be considered a "good" label has a number of characteristics, among them its legibility, and the degree to which it contributes to a harmonious and visually pleasing display. Thus, there is a balance to be struck between making the label easily readable, but not so ostentatious that it overpowers other, and possibly more important, details within the map. Another potential challenge is keeping each label, in accordance with general map-making convention, within the boundaries of, or adequately adjacent to, whatever it is intended to be labeling. Treasure Island in the map above, for example, isn't wide enough to accommodate its label at the appropriate text size, and thus the decision to change its orientation. Small choices such as these, and a plethora of various others, lead to useful labels and a functional map.
Map projections and coordinate systems are at the heart of a map's utility as location and navigational aid. The principles involved in selecting and/or analyzing a projection or coordinate system for a map are intuitive in nature, but the underlying concepts can become a bit complicated.
This map of Michigan is projected using the Hotine Oblique Mercator Azimuthal projection, which is an intimidatingly lengthy name, but means that this is a cylindrical, oblique version of the Mercator projection. As such, it is conformal, and displays the state as accurately shaped. This particular projection is suitable for Michigan because it doesn't divide the state into multiple zones, like a State Plane or UTM grid would, as the state encompasses multiple zones of both. Also, as this is intended to be used as a general reference map, the projection is well suited because of its conformal nature, which preserves the distinctive mitten shape of the lower peninsula.
