Bad map vs. Good map

BAD MAP!

Map generated July 4, 2009.

http://www.cpc.ncep.noaa.gov/products/stratosphere/uv_index/gif_files/uvi_usa_f1_wmo.gif will give you a map for today.

The UV index is an international standard measurement of the strength of ultraviolet (UV) radiation from the sun, used as a forecasting tool for the public to help protect against UV overexposure. The index is an open-ended linear scale, with an index of 10 corresponding to midday sun on a clear-sky day.  Higher index values represent a higher risk of skin damage from UV exposure.

This is a bad map because of the color scheme chosen.  The steps can be hard to distinguish, and the rainbow order is misleading.  One might expect the bright orange to red areas to represent the areas with the highest UV radiation levels, instead of less than midday sun intensity.  Further, when the World Health Organization (WHO) standardized the UV index, they suggested standard colors and graphics for printed media, which are not used here.

GOOD MAP!

http://en.wikipedia.org/wiki/File:Somalian_Piracy_Threat_Map_2010.png

Aside from the typo (Ethiopia), I like this map. The proportional symbols for major ports and trade routes are simple (even if Singapore is a little distracting) and give just the right amount of geographical information. The expanding range of pirate attacks shown in gradational bands by year captures the chronology of data.