Geography 140
Introduction to Physical Geography

Lecture: Map Symbolism

IV. Map symbolism has become pretty standardized through the centuries, so
that even foreign maps are not all that hard to read. The important
requirement for map symbols is that they be readily recognizable and
suited to the scale of the map. We can group map symbolization into
three major categories: pictorial symbols, colors symbolism, and value
symbols.

A. Pictorial symbols involve using neat little pictures to express what
is found at a particular place on a map, such as a building, a well or
spring, or a mine (these are such small entities that only a
relatively large scale map would bother including them). The United
States Geological Survey (USGS) puts out all sorts of beautiful and
communicative maps, and their pictorial symbols are typical of the
sort. I am going to send you to two large files at the links below,
which are the left and right side of the key to pictorial symbols that
the USGS uses. Make sure to have a look at both of them to get an idea
of common symbols:

Left side of key
Right side of key

B. Color symbolism has settled into pretty common usage.

1. Blue is used to show water features: rivers, springs, lakes,
playas, oceans, reservoirs, canals.

2. Green is used to represent vegetation (both natural and human-
maintained): forests, marshes, scrublands, orchards, vineyards.

3. Brown is often used to show topography or terrain.

4. Black is used to show human artifacts, such as individual
buildings, including schools, churches, cemeteries, homes,
outbuildings, railroads, pipelines, power lines, oil wells, and
tanks.

5. Red is also used to show many larger human artifacts, such as
highways, roads, townships, and urban built-up areas on relatively
smaller scale maps where it wouldn't make sense to show every
building.

6. The USGS also uses purple to show the same things that would
normally be shown in red when they revise a map, in order to
highlight changes since the last time they revised it. So, you can
see how Southern California has grown over the last few decades by
looking at all that purple!

Here's a map showing some of these for Iowa City, IO. Note the
elevation contours, the red areas for older urbanization, and the
purple areas showing more recent urbanization:

http://www.lib.utexas.edu/maps/united_states/iowa_city_io_1983.jpg

C. Value symbols not only identify something and show its location, they
also tell us something about the amount of that something in
that location. The need to represent values as they change across
space has led to a variety of different map types:

1. Dot maps tell you how much of something is found somewhere through
concentrations of dots. Each dot might stand for one individual or
one case, or it could stand for multiples (e.g., each dot stands
for 10 hectares planted in wheat; each dot stands for 1,000 head of
cattle). Usually, only one distribution is shown as dots against a
skeletal location map. Sometimes, you may see two distributions,
shown by different colored dots, on a simple location map.

Here is a simple dot map of EPA Superfund cleanup sites in the U.S.:

http://www.scorecard.org/env-releases/land/

Here's a dot map of zebra mussel sightings (zebra mussel is a very
problematic invasive exotic species of shellfish that originated in
the Black Sea, the Caspian Sea, and Lake Aral. It has created
ecological mayhem in the American Great Lakes and clogs water
supply pipes for hydroelectric ... and nuclear power plants. This
critter is major bad news). The map shows two kinds of patterns.
The known aquatic distribution in the Great Lakes and the
Mississippi and St. Laurence drainages is shown with red dots. The
dryland sightings (mainly larvae attached to boat hulls that were
being driven across country) are shown with yellow stars:

http://nas.er.usgs.gov/taxgroup/mollusks/zebramussel/maps/current_zm_map.jpg

2. Graduated symbol maps allow you to draw your reader's eye directly
to really big concentrations of your distribution by showing them
as circles or squares or rectangles that vary in size in some way
that is proportionate to the concentration in an area. A very
common example of such a map is a population map, where small towns
are shown as dots and large towns and cities are shown as graduated
circles. Here is one showing the relative size of shopping centers
in the Atlanta, Georgia, area, with the key to their square footage
in a legend:

http://go.owu.edu/~jbkrygie/krygier_html/geog_353/geog_353_lo/geog_353_lo06_gr/simplemap.jpg

Here's another, showing the relative availability of hotel rooms in
and around the Quad Cities (Illinois and Iowa), in case you were
planning a convention of a particular size. This map puts the data
(number of rooms) in the graduated symbol, rather than in a legend.

http://www.chicagocarto.com/images/quadcities.jpg

3. A divided circle map shows the relative value of something or other
by the size of the graduated symbol but then breaks that symbol up
in a way that allows you to see, not just relative size, but
composition. Here is a map of relative industrial activity in
western Germany (back when it was called "West Germany"), where the
importance of an industrial center is implied by the size of the
circle representing it. The map divides these circles into pie
slices showing the proportion of each city's businesses that fall
into particular categories (e.g., iron and steel, electrical
engineering, chemicals, etc.), so you get a sense of the economic
"personality" of the town. This way, you get two different kinds
of information from the map with one symbol
that is easy to interpret.

http://www.lib.utexas.edu/maps/europe/west_germany_ind_1972.jpg

4. Bar chart maps can similarly show the relative local importance of
various categories by the relative height of the bars (or you could
just subdivide one bar proportionally). Here's an example that
shows educational attainment in the Census tracts around Boston.
It's a little "busy" with seven classes, and the height of the
different columns is a little hard to interpret, but it does
illustrate the possibilities of visualizing data spatially in this
way:

http://www.gsd.harvard.edu/gis/manual/normalize/ed_attainment.jpg

5. Other graduated symbol maps are possible, which can convey three or
more ideas simultaneously. Here's a map entitled, "Life in Los
Angeles." It was done at CSU Northridge by Dr. E. Turner and Mr. R.
Doss in the late 1970s and showed four aspects of urban population
geography in various parts of the City of Los Angeles by a "face"
symbol (happy faces were all the rage back then). Affluence was
shown by the roundness of the face (a round face meant high income,
a slender face meant middle income, and a skinny face meant low
income); unemployment rate by whether the mouth was upturned,
downturned, or a straight line; "urban stresses" by whether the
eyes had raised, straight, or scowling eyebrows; and racial
structure of the population by three shadings of the face. At a
glance, you could see the correlations among race, income,
unemployment, and quality of the urban environment through the
variations in this one graduated symbol pattern.

http://www.csun.edu/%7Ehfgeg005/eturner/gallery/lifeinla.GIF

6. Flow maps can show the origin(s) of some flow (e.g., water in
rivers or in managed water systems, money, oil, migration of
animals or humans), its desination(s), and its magnitude by arrow
symbols which point from some places to others and vary in
thickness. Here is one showing the global flow of crude oil in
1997:

http://www.eia.doe.gov/emeu/security/oilflow2.gif

7. Cartograms are bizarre-looking maps, in which the areas of spatial
features themselves are distorted in proportion to the value of an
attribute. The features generally don't preserve the shape of the
areal units being mapped, but you know which one is which by its
relative position. So, you could have North American populations
by country shown as three rectangles, with the huge rectangle
standing for the USA being underneath the much smaller one for
Canada and above the intermediate tall rectangle for Mexico.
People are experimenting with animating these, too! A wonderful
example was done by the New York Times of the 2004
elections. It is interactive, in the sense that you pick whether
you want to see the data faithful to the geography (resulting in a
red-blue choropleth map) or see the data weighted by the states'
populations (which gives you a sense of the popular vote):

http://www.nytimes.com/packages/html/politics/2004_ELECTIONRESULTS_GRAPHIC/

Here's another cartogram of the 2004 presidential contest by Suresh
Venkatasubramanian, but this one is broken out by county, not
state:

http://www.personal.psu.edu/cab38/GEOG321/14_multivariate02/Suresh_cartogram_purple.jpg

Here's an animated cartogram that cycles through global data on
population, elderly population, net immigration, tourist
destinations, and refugee origins:

http://www.sasi.group.shef.ac.uk/images/cartogram_animation.gif

D. Choropleth maps are really simple maps, as simple as dot maps. You
set up a few categories of something you're interested in (e.g., rock
types, soil types, vegetation types, types of agriculture, climates,
or such human phenomena as language areas, dominant religions,
population density, wealth and poverty, numbers of executions). You
then assign colors or ink patterns to indicate each category on your
map (e.g., sandy, silty, clayey, or loamy soils; high income, medium
high income, medium income, medium low income, and low income). Then,
you fill the right areas on the map with the appropriate color for
that area. These maps, if shaded properly (good contrast among a
small number of categories and a consistent transition from lighter to
darker to express values from lower to higher or higher to lower), are
easily interpreted by most readers. They do have the problem of
coloring an entire area with one color, even if the underlying
distribution might vary a lot within that one area. The advent of
Geographical Information Systems (GIS) has made this one of the most
popular map types around (because choropleth maps are really easy to
make in a GIS) and caused a reduction in the use of some other map
types that might be better able to communicate in certain situations.
That said, one nice new development is that of the animated choropleth
map for use on the Internet.

Here is a map of, er, animal waste concentrations among the 50 states
(note the evocative color ramp the Scorecard folks used -- eeeeeuw):

http://www.scorecard.org/env-releases/aw/index.tcl

This is an animated choropleth map showing the countries with bee
industries affected by the varroa mite. The varroa mite is a spider-
like parasite on honeybees. As many of you may have heard, bee
colonies all around the world have been struck with "colony collapse
syndrome," in which the worker bees never return to their home hives
to feed the queen and "baby bees." No-one knows what is going on, but
it threatens world agriculture, because many crops depend on bee
pollinators. There are all kinds of hypotheses, but one is that the
varroa mite might be partially responsible.

http://www.agric.wa.gov.au/ikmp/images/beemap.gif

E. One of the more sophisticated map types is the isoline map (sometimes
isolines are called isarithms or isopleths). Isolines are any line on
a map, which connects all places having the same value of "something
or other," whether it be rainfall receipt, air pressure, elevation,
or .... latitude and longitude! Meridians are isolines of longitude,
and parallels are isolines of latitude. So, you've already bumped
into this concept. Well, it can be used for all sorts of other
"stuff" than latitude and longitude and it very effectively conveys a
third dimension in a two-dimensional map.

1. Some types of isolines include:

a. Isohyets connect all places in an area having the same
precipitation, whether on the same day or averaged out over a
long time. This map shows 12-month rainfall totals in
Australia:
http://www.bom.gov.au/cgi-bin/climate/rainmaps.cgi?page=map&variable=totals&period=12month&area=aus

b. Isotherms connect all places having the same temperature (e.g.,
the same daytime high or nighttime low on a given day or the
same average annual temperature or the same average January
nighttime low). This map illustrates the concept by showing
mean maximum temperatures over the course of a year in
Australia:
http://www.bom.gov.au/cgi-bin/climate/tempmaps.cgi?page=map&variable=tmaxav&period=12month&area=aus

c. Isobars connect all places having the same barometric or
atmospheric pressure. Here is one showing a high pressure and a
low pressure center near New Zealand and Australia:

https://home.csulb.edu/~rodrigue/geog140/isobarsnewzealand.gif

d. Isogons connect all points having the same compass deviation.

i. True north is not the same as magnetic north: They're
presently misaligned by about 1,600 km (1,000 mi.), which
puts the magnetic north pole in Canada, at Prince of Wales
Island in the far north of the country.

ii. This can mess you up if you are using a compass to navigate
around when you're hiking, especially if you're in an area,
where the angle between your location, the North Pole, and
the magnetic north pole is fairly wide (that angle is
called magnetic declination).

iii. Some maps, especially USGS and similar maps, show magnetic
declination as an angle formed by two arrows, one pointing
true north and the other pointing to the magnetic north
pole. The magnetic declination is normally stated in
degrees and a date given (because the magnetic north pole
wanders a bit through time, just to mess you up some more).
You lay the map down under your compass and fiddle with it
until the magnetic north pole line aligns with the compass
arrow. Then your map will be aligned so that north on the
map points to north in the landscape you're in. You can
now take some decent bearings to get yourself un-lost and
back to camp before sunset!

iv. There are maps of magnetic declination that show you what
the typical difference between true north and magnetic
north is in a particular area. They connect places having
the same delination with isolines called isagons.

v. So, please visit the map linked just below vi and figure
out about how many degrees east magnetic north would be
from true north in our Los Angeles-Long Beach area
(interpolate between the two isagons that bracket Our Fair
City).

vi. Which major American city would have its compasses pointing
true north? Which one would have the most seriously
misaligned compasses? San Francisco? New York? Boston?
Chicago? New Orleans? Seattle?

http://www.gly.fsu.edu/~kish/field/projects/p4/isogon2.gif

vii. Just to drive you nuts, some folks use the word, "isogon,"
to mean an isoline of constant wind direction and others
use it to describe an equilateral polygon in geometry. Oh,
well.

e. Contours connect all points having the same elevation. You can
see how they are constructed in the cross-section below, where
every place at the same elevation on a mountain is sliced with
an imaginary plane at that elevation. If we imagined a line
being left on the mountain showing the slice, we could then turn
the image over so that we're looking directly down on the
mountain and see the slice lines as a series of concentric
circles coming together around the peak of the mountain!

f. Isochron maps connect all places the same time interval from or
to some reference point. For example, you could map how long it
takes for the primary waves from a particular earthquake to
reach various seismic recording stations. Here is a map showing
how long it would take to go from Cambridge (or get to
Cambridge), England, using the British railway system.

http://www.mysociety.org/2006/travel-time-maps/rail-cambridge-1500px.png

g. You can even combine two isoline maps in one, if you're really
careful about color use. Here is a really nifty map that
superimposes isobars as solid lines on top of isotherms shown as
the boundaries between colors that imply hotter or colder. This
is updated each day:

http://ww2010.atmos.uiuc.edu/(Gh)/wx/cwp/prods/current/sfctmpslp/sfctmpslp_N.gif

2. Isoline maps convey a lot of precise information by letting you
infer what the values of any particular spot are by noting how far
it is to the two nearest isolines and interpolating its exact value
by its relative distance to each of them. So, a point one fourth
of the way from an air pressure reading of 1016 millibars to one of
1020 millibars could be read as having an air pressure that time of
1017 mb. You engaged in this kind of interpolation when you
figured out the magnetic declination in Long Beach (~15°E of
true north).

3. A contour map can be turned into a shaded relief map, which puts in
shadows and bright areas as though the map were being lit from one
spot. It makes the map look more suggestive of a real terrain,
with the third dimension sort of popping out at you. Here's a nice
example of Pike's Peak in Colorado from MindBird Maps & Books:

http://www.mindbird.com/2f770f2f0.jpg

4. Sometimes people combine the third dimensional virtues of the
isoline map with the easy interpretability of the choropleth map by
shading in the areas between key isolines. So, for example, you
can shade contour line maps so that really high elevations are red,
high elevations are brown, medium elevations are yellow, low
elevations are chartreuse, and really low elevations are dark
green, or you can use any other continuum of colors to do the job.
The colors you use to represent different elevation ranges are
called "hypsometric tints." By adding hypsometric tints, you have
the precision of isoline maps (you can interpolate any location's
elevation, for instance) and the visual generality of color. Your
eye is immediately drawn to the high spots and the low spots,
without needing to sit around and interpolate. Here's a nice
example from up in Idaho:

http://www.uidaho.edu/biogeochemistry/images/mickey_hs_contour.gif

5. A newer development involves combining these hypsometrically-
tinted maps with the idea of shaded relief at the same time. These
can really create a stunning effect if the hypsometric tints are in
a narrow color range, from green to brown, so that the map looks
like a realistic landscape.

Here's a nice example of a hypsometrically-tinted contour map of
Southern California:

http://geology.com/news/images/shaded-relief-map.jpg.

Here is a really great example generated from the Mars Orbiter
Laser Altimeter data for the planet "next door," with place names
supplied by yours truly. Mars has FAR greater elevational contrast
than anything on Earth, so the green/brown palette will not do it
justice. So, this map uses a huge range of vivid colors from black
to white. It ramps from black/purple/blue for the lowest
elevations up through green, yellow, orange, red, brown, beige, and
white for higher and higher elevations. The result seems to bias
the reader into supporting the arguments that Mars once had oceans
and seas, doesn't it?

https://home.csulb.edu/~rodrigue/mars/MOLAmercatorlabel.jpg

6. There are all sorts of experiments with animated maps, which take
the USGS electronic version of contours (digital elevation models)
as the basis of animated fly-throughs or rotating blocks. So far,
these are more golly gee-whiz special effects than devices for
communicating too much knowledge, but they are pretty cool. If you
have a fast connection and a little time, do check out the fly-
through of the great Martian canyon, Valles Marineris, prepared for
NASA by JPL and Arizona State University:

http://video.google.com/videosearch?q=Valles+Marineris+fly+through&hl=en

F. Haptic maps, or maps that use sound to convey information, are
emerging as interesting augmentations of mapping. They could be used
to allow blind or visually-challenged people to make use of maps
designed around this other sense. Here's an example of a haptic map
for navigating around UC Santa Barbara:

http://soundscapes.geog.ucsb.edu/sound_touch_map/flash/mapinterface3.html

Here is an animated, haptic map of the Coalition casualties in Iraq
from 20 March 2003 until 13 February 2007 created by Tim O'Bleek.
This is a dot map, in that each dot represents one soldier's death and
its haptic equivalent is a soft tick sound, rather like you'd hear on
an old typewriter in a newsroom. Each death is accompanied by a large
red dot which fades over a month through pink until it disappears,
leaving only the black dot. If there is a concentration of deaths in
one area on one day, O'Bleek expresses that by using a more intensely
red dot and a louder ticking sound. The map is also interactive, in
that you can select which Coalition country's casualties to view or
not view, and you can ask to see major place names, too. This is a
heartbreaking cartographic representation of the geography of
soldiers' deaths through time and an affecting memorial to their
sacrifice (and that of their families and friends):

http://www.obleek.com/iraq/

G. Cartography is undergoing many changes now with the increasing use of
computer-aided design (CAD) technologies, mapping packages and other
graphics software, and geographical information systems (GIS).

1. GIS are extremely powerful, fully-searchable relational database
management systems (RDBMS) that handle spatial data and, best of
all, perform all sorts of spatial analyses on them and put out the
results as maps (with tables and graphs, if you so choose). It's
their spatial analytic capacities that set them apart from other
RDBMS and from computerized mapping packages.

2. To imagine what they're capable of, think of a virtual transparency
containing a map of, say, the rivers and water features in an area.
Now imagine another virtual transparency, say, a contour map of the
local topography. Then, another map of vegetation in the area.
What about another virtual map of land use patterns by parcel?
Keep on adding imaginary maps on virtual transparencies to your
heart's content.

3. Now, imagine overlaying all of these transparencies on an overhead
projector or light table to find all the areas that are within 100
meters of a river, on slope angles less than 10 percent,
historically covered with riparian (riverside) vegetation, and that
are not presently developed, so that you can identify riparian
habitat that should be preserved through zoning codes.

4. After overlaying just a few of these transparencies, you probably
would not be able to pick out the areas of interest to your
planning agency, would you? Well, this is what the GIS can do for
you! It can analyze every bit of land for all of that stuff --
dozens of virtual maps -- and create new maps of the results of its
analysis. These things are really cool, and there are some
stunningly well-paid jobs for graduates with solid training in GIS,
cartography, and spatial statistics. You can get that training as
a geography major or by getting our GIS/cartography certificate.

Well, that's enough for your whirlwind introduction to map symbolization (and
maps in general). I apologize for using links to illustrate this lecture.
Some of the images are quite large, so I didn't want you to be sitting there
on your 28.8K or 56K modems, stewing during an eternal download. It's faster
to just send you to one graphic at a time for shorter downloads, but I know it
is a pain to be pointing and clicking.

I hope you come away from this with an appreciation of maps as art and as the
effective communication of scientific and historical content. Later on in the
semester, I'll have a lab on contour mapping. Right now, I want you to focus
on the first exam, which will cover these eleven lectures and the first two
chapters in your textbook. In your studying, focus on major concepts,
definitions, processes, not so much on memorizing facts and figures. Have as
good a week as getting ready for an exam permits!

Geography 140 Introduction to Physical Geography

Lecture: Map Symbolism

Geography 140
Introduction to Physical Geography