Addressing some map-related misconceptions

^ date reposted to this blog
Feb. 01, 2022: originally posted to my old blog

Our planet is spheroidal in shape, which means its surface is curved. So making a map of the Earth's surface involves taking something that is curved and projecting it onto something flat (such as a piece of paper or a computer screen). But this flattening inherently causes some distortion from reality. It is not possible for any one map projection to preserve all of the following: 1.) direction, 2.) shape, 3.) area, and 4.) distance. So when a cartographer chooses a particular map projection, they are choosing to preserve one or more of those traits at the expense of others.

Maps of the 48 states often use the Lambert Conformal Conic projection. Even if you are not familiar with that term, it is a map projection with which we are all quite familiar; many cartographers use it because it is a great choice for mapping the 48 states. It preserves shape well, and it comes reasonably close to preserving area and distance too. However, all map projections must distort something, and in the case of the LCC projection, the thing that gets distorted most is direction. Most maps of the 48 states omit graticules, and perhaps for that reason many people are not aware that directions are not consistent on an LCC map. The image below shows a conic map with graticules, and it serves to illustrate that the cardinal directions for a point on one side of the map have different angles than those same directions on the opposite side of the map:

That also illustrates the fact that an LCC map should never include a north arrow! But since LCC maps usually omit graticules too, people tend to assume north is... well, just "up". As a result, I would say the following are the biggest misconceptions about direction in the U.S.:

• California is not as far west as many people think;
• Texas is not as far south as many people think;
• Florida is not as far east as many people think;
• Maine is not as far north as many people think, but...
• Maine is farther east than many people realize.

In an attempt to correct those last three misconceptions, I created the infographics below. These images cannot be considered "maps", although they do resemble maps in the sense that the graphic elements are arranged geographically; and also some things have been distorted in order to emphasize certain truths.

For the first one, this is essentially what I did:

• Each of the northern tier states (i.e. those along the Canada border) were plotted as bars on a graph. These bars illustrate the north-south span of each state (according to latitude).
• Selected cities within each state were plotted as dots, again according to their latitude.
• The states were then arranged geographically (from west to east). The states were not moved north or south, so all latitudes remained accurate across the graph. For example, the image indicates that Boise, Idaho, is at the same latitude as Portland, Maine, and that is correct.
• More to the point, it is also true that parts of six states extend further north than anywhere in Maine.

(You may have to tap on the images below in order to bring up a more legible version)

This second graphic was done in essentially the same way, although it is slightly more complicated:

• Each state east of the Mississippi River was plotted as a bar on a graph. These bars illustrate the east-west breadth of each state, based on longitude west of Greenwich (or the Prime Meridian).
• Selected cities within each state were plotted as dots, again according to their longitude.
• The states were then moved north or south in order to display the information legibly (most neighboring states have at least some east-west overlap, so they could not be arranged side-by-side). This resulted in further distortion of the direction and distance between cities and states. However, the states were not moved east or west, so all longitudes remained accurate. For example, the graphic indicates that Myrtle Beach is due south of Buffalo, and that is true.
• More to the point, it is also true that ten entire states (as well as parts of five other states) are further east than anywhere in Florida.
• Florida is not due south of New York or Pennsylvania; rather it is most closely aligned with Ohio.
• Also, notice that Maine extends much farther east than every other state.

I could have illustrated these same points with a map that uses a cylindrical projection (such as Mercator), but sometimes extraneous information (like state lines and coastlines) can obscure the main point. The method used here makes it easier to visually compare latitudes and longitudes of the selected states and cities.