Color progression Choropleth map

single hue progression

single-hue progressions fade dark shade of chosen color light or white shade of relatively same hue. common method used map magnitude. darkest hue represents greatest number in data set , lightest shade representing least number.

two variables may shown through use of 2 overprinted single color scales. hues typically used red white first data set , blue white second, overprinted produce varying hues. these type of maps show magnitude of values in relation each other.

bi-polar color progression

bi-polar progressions used 2 opposite hues show change in value negative positive or on either side of either central tendency, such mean of variable being mapped or other significant value room temperature. example, typical progression when mapping temperatures dark blue (for cold) dark red (for hot) white in middle. when 1 extreme can considered better other (as in map of life expectancy) common denote poor alternative shades of red, , alternative green.

complementary hue progressions type of bi-polar progression. can done of complementary colors , fade each of darker end point hues gray shade representing middle. example using blue , yellow 2 end points.

blended hue color progression

blended hue progressions use related hues blend 2 end point hues. type of color progression typically used show elevation changes. example, yellow through orange brown.

partial spectral color progression

partial spectral hue progressions used map mixtures of 2 distinct sets of data. type of hue progression blend 2 adjacent opponent hues , show magnitude of mixing data classes.

full-spectral color progression

full spectral progression contains hues blue through red. common on relief maps , modern weather maps. type of progression not recommended under other circumstances because color connotations can confuse map user.

value progression

value progression maps monochromatic. although color may used, archetype black white intervening shades of gray represent magnitude. according robinson et al. (1995). best way portray magnitude message map audience. understood user , easy produce in print.

usability

when using of these methods, there 2 important principles: first darker colors perceived being higher in magnitude; second that, while there millions of color variations, human eye limited how many colors can distinguish. generally, 5 7 color categories recommended. map user should able identify implied magnitude of hue , match legend.

additional considerations include color blindness , various reproduction techniques. example, red–green bi-polar progression described in section above cause problems dichromats. related issue color scales rely on hue insufficient variation in saturation or intensity may compromised if reproduced in black , white. conversely, if map legible in black , white, prospective user s perception of color irrelevant.

color can enhance communication between cartographer , audience, poor color choice can result in map neither effective nor appealing map user. simpler better.

a choropleth map (top) , dasymetric map (bottom) of population of san francisco bay area in 2000.