Friday, April 18, 2008

Apple #311: Maps

Yesterday I woke up thinking about maps. Don't ask me why, I just was.

Here's what I was thinking: maps give you so much information. But they represent the three-dimensional world in a two-dimensional format, so by necessity they have to leave some things out. They can't tell you everything about a particular location because that would just be a reproduction of that place; they have to choose only certain things to tell you. The question then becomes, what certain things does the map-maker think are the most important things for you to know?

Consider the treasure map. On your typical treasure map, you usually get mountains (noted with little upside-down v's), maybe a river or some other body of water, a dashed line showing you where to walk from where you are standing to the place where the treasure is buried, and then a gigantic X. The X, clearly, is the most important thing on the map. Everything else is there to tell you how to find that X. It's thus-and-so far from the mountains, you have to cross this river, find this type of tree and dig under it, etc.

Map drawn of the Lost Dutchman mine, believed to be in Arizona near the Superstition Mountains. Hundreds of people have tried to find the gold which is supposedly somewhere near the Needle, but the gold's exact location remains a mystery. Apparently this map wasn't as good as it could have been.
(Map posted by the Superstition Mountain Museum)

There might be all sorts of other trees, or other rivers than the ones noted on the map but only those on the map are the important ones because they somehow indicate the position of the treasure.

So a map a selective instrument, but an extraordinarily useful instrument precisely because of its selectivity.

Hey, and before you decide maps are boring, consider this: "87 percent of Internet users have done online mapping, leading all other online activities including news, e-commerce and gaming." (Source: Pittsburgh Post-Gazette)

  • The science of map-making is called cartography.
  • If you're making a map of anything on the earth, it will inevitably be distorted to some extent. This is because the earth is a sphere, and your map is flat.
  • To this, some people would say, that's why globes rule! And I like globes, too. But you can't fold up a globe and put it in your pocket.
  • The unavoidable distortion inherent in maps has been the subject of great controversy among map makers for several decades.
  • The main method of making maps (that's a lot of M's) since the 1500s was the Mercator projection method. It's based on the grid of latitude and longitude, and it's supposed to have been especially useful for people sailing across the ocean because it gave an accurate indication of how to set your compass to get to a particular location.

Map drawn using the principles of Mercator projection
(Image from Matt Rosenberg's article)

  • However, the distortion created by the Mercator method made places like Greenland and the South Pole look enormous, and it also made Europe look much larger than it actually is. So lots of people called Mercator maps "racist" or "colonialist" or "Eurocentric," etc.
  • An alternative method was proposed in the 1970s by a journalist named Arno Peters. This map was also based on the longitude and latitude grid, but he had a poor understanding of the mathematics of cartography, so his resulting map was even more distorted than Mercator's, just in a different way. But he said that his map was "non-racist" and "fairer" to the third world and so on, and lots of people bit based on that description alone.

Map drawn using the Gall-Peters projection method
(Image from Matt Rosenberg's article)

  • In the 1980s, organizations like the National Geographic Society and others began using maps which balance the latitude-longitude projection with less distortion of places at high latitudes (close to the poles). The shapes are not as accurate, but the sizes are more accurate relative to locales closer to the Equator. These types of projections are more commonly used on maps made today.

Map made according to the Robinson projection method, and probably the way most world maps you see today will look.
(Image from Matt Rosenberg's article)

  • People who really care about how maps are made say that the Mercator and Peters types of maps shouldn't even be sold any longer, and these people are scandalized that some companies are even still selling Mercator and Peters maps.

But all that is really getting into the nitty and the gritty about maps. I'm more interested in the kinds of maps. And there are probably about as many types of maps as there are things in the world that you'd want to tell people about.

  • Political maps -- these indicate boundaries of countries, states, and cities, bodies of water, and maybe other details like major roadways, but generally there's really big blocks of color on these maps.

Political map of Africa, with the colors signifying different countries. Capitals are noted with red dots and named in lower-case letters. Countries are named in upper case.
(Map from Maps of

This political map is of the State of Texas, so in this case, the unit of measure isn't by country but by county.
(Map from Texas Maps)

  • Road maps -- these are like what you get from AAA or at the gas station, and their primary feature is roads: highways, expressways, two-lane roads, railroads, bridges, overpasses and exit ramps, etc. Road maps will also show the borders of states or counties, but the real reason you want this map is for the roads.

Road map of downtown Chicago. Sorry it's so huge, but when I reduced it, it was too small for you to tell what it was. Road maps are what most people want on a regular basis. They want to know how to get to their friend's house, or to that new restaurant they've never tried, or to their new job, or to the nearest train station, etc. Road maps can help you do all of those things.
(Map from

  • Physical maps -- these use color and shading to show the physical features and elevation of an area. Mountains are in brown and they look bumpy, water is blue and deeper water is darker blue, lower elevations are in green, and so on. There might also be some indication of boundaries or cities mixed in with the physical depiction, but the main thing going on here is the colors.

Here's a physical map of North America. Country borders are shown, but states and cities are not indicated. Instead, you get mountain ranges, major bodies of water, and land masses like the Great Plains or the Coastal Plain. Colors indicate changes in elevation (brown = higher, green = lower).
(Map from Free World Maps)

  • Climate maps -- these maps are also similar to physical maps, but in this case, the colors are used to indicate temperature and precipitation. Places that get lots of rain are represented in green; places where it's almost always icy are in white; deserts are light brown, etc.

Climate map of Africa. Boundaries are drawn to show countries within Africa and major cities are indicated, but the real focus is on the varying colors, used to indicate different climate regions on the continent. I always thought of Africa as mostly desert, which this map does show. However, it also says that lots of Africa is tropical. In fact, according to World Book, Africa has the largest tropical region of any continent. That's news to me.
(Map from World Book Online)

  • Topographical maps -- these are like physical maps in that they use color but instead of making mountainous areas look bumpy like mountains, they'll use parallel lines drawn close together to indicate areas of higher elevation. Often the lines of latitude and longitude will be included too, as well as principal roads or other major landmarks. The military uses these kinds of maps, and so do people who plan where to build things or dig things, and people who do a lot of camping or hiking. Personally, I find these maps really hard to read.

Topographical map showing the region around Mt. Evans in Colorado. Gad, I have looked through this site's several maps and photos of the mountain and its three smaller peaks nearby, and I cannot figure out where anything is. If you want the Apple Lady to go hiking with you, don't give her the topographical map.
(Map by National Geographic Society and posted by the 14ers)

  • Nautical charts -- these maps are made specifically for people who will be boating or sailing in particular bodies of water. Nautical charts can include tons of information helpful to a boater, such as water depths (often indicated in plain numbers by themselves), distance a boater must keep away from the shoreline, overpasses with clearance heights, location and signaling times of buoys, the position of hazardous objects, rise and fall of the tides, and more. If you're going boating, better get yourself a nautical chart of the area.

Nautical chart of coastal Massachusetts, as generated by NOAA's fancy MassGIS database. The numbers by themselves indicate water depths. Purple and green markers indicate buoys. Lines around the coast indicate areas too close to the shore for cruising. Note the lines onshore, which indicate topographical elevation.
Please do not use this image for navigation purposes, but get an updated chart.

  • Economic or resource maps -- these maps will show you major political boundaries, but the real focus of the map is to show you where certain resources are concentrated. For example, you might see a map of the United States that shows which areas grow lots of corn, where beef and dairy cattle are raised, where people grow lots of soybeans, etc. In elementary school, I used to find maps like these sort of boring -- I wanted to get to the hard facts! Tell me where the capitals are! Don't waste my time with these little pictures! -- but now, I think these kinds of maps are my favorite.

This resource map shows where all the beef cattle were raised in the U.S. in 1997. I had no idea that beef cattle lived pretty much all across the country.
(Map from USDA 1997 Agricultural Atlas)

Judging from the availability of apples in pretty much every grocery store around the country, you might think apples were grown in lots of places around the country, wouldn't you? Not so, says this map. Chances are, a good apple has traveled some distance to get to you.
(Map from USDA 1997 Agricultural Atlas)

See how much there is to learn from resource maps? Here are some more:

The resource highlighted in this map of Oklahoma is wind. The darker red, the better the wind for the purposes of generating power. Right now, there are tons of resource maps on the Internet showing locations ripe for alternative power sources, from wind and solar energy to buried forest material.
(Map posted by the University of North Dakota Energy & Environmental Research Center)

This is just a portion of a resource map that Dr. Steven Huffman made. In this case, the resource is language. Dr. Huffman re-categorized all known human languages into broad groups and then mapped those groups using a couple of different computerized mapping programs. The above is the kind of thing you can see if you download the world map. He has other, more detailed maps as you drill in closer to any given region. Really fascinating stuff. Hey, I wonder if you can make any conclusions by overlaying that climate map I posted above with this language map of Africa...

Want more maps? Maybe topographical maps of Mars? How about historical maps of the Battle of Gettysburg? Or the whereabouts of phytoplankton? New maps and new mapping discoveries are being made all the time, and Map Watch News is ready to keep you posted.

Matt T. Rosenberg, "Peters Projection vs. Mercator Projection,", Geography
Fact Monster, World Geography, Types of Maps
USGS Explorers, Special Topics, Maps and Images
Office of Coast Survey National Ocean Service What is a Nautical Chart
Boat, Chart Reading 101

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