Learning About Projections Using ArcGIS

Table of Contents

  1. Learning About Projections Using ArcGIS
  2. Setting Up Your Workspace
  3. Downloading Data from Natural Earth
  4. Adding Data to ArcMap
  5. Symbolizing the Map by Subregions
  6. Exploring Map Projections
  7. Choose Your Projection

Exploring Map Projections

In this chapter, you learned that Earth is spherical. However, maps still managed to represent Earth using a flat plane. A flat representation is made possible by using map projections. A map projection is a geometric transformation of the round Earth onto a flat plane using mathematical equations. The process of transforming a spherical object onto a flat plane distorts area, shape, distance, direction, and continuity. These are known as the five preserved properties because some map projections can maintain one or more of these characteristics with a high degree of accuracy. However, no map projection can retain all five of these qualities at the same time.

In ArcMap, the data frame window displays the map using project-on-the-fly. Even though the layers in the Table of Contents might use different projections and coordinate systems internally, ArcMap tries to line them up on the screen using the coordinate system defined in the data frame properties. What this means is that you can change the projection in the data frame to alter the appearance of the map onscreen without modifying the original data files.

Cylindrical Projections

Cylindrical projections transform the globe onto a flat plane using a cylinder as the developable surface. In this step, you will use ArcMap to explore one of the most commonly used cylindrical projections, the Mercator.

Open the properties for the world map data frame. Navigate to the Coordinate System tab. Expand the Projected Coordinate Systems folder.

An image of the Coordinate Systems tab for countries layer
The Coordinate Systems tab in the data frame properties allows you to choose a spatial reference system from two main folders, Geographic Coordinate Systems and Projected Coordinate Systems.

Scroll down until you see the World folder. Expand the World folder and select Mercator (world). When you are ready, click OK. Click Yes, when the warning appears. On the Tools toolbar, click the Full Extent button, which looks like a globe.

An image of the full extent button for world map
The Full Extent button zooms to the extent of all the data on the map.

Take a moment to review the chapter text regarding the Mercator projection. When done, continue to the next step.

An image of the Mercator projection for world map
The Mercator projection maintains the shape (conformity) of the continents, but the sizes get altered dramatically. Click to view the image in a larger size.

By default, the Mercator projection centers on 0 degrees longitude. However, in ArcMap, you can customize map projections to a certain extent. What you are allowed to do varies by map projection. For the Mercator projection, it is possible to center the map on any longitude you wish. In this step, you will align the map on the opposite side of the globe, 180 degrees longitude.

Open the properties for the data frame and navigate to the coordinate system tab. Double-click on the Mercator (world) projection. When the Projected Coordinate System Properties window appears, change the name to “World Mercator 180.” In the Value field for the central meridian, enter 180. When done, click OK. Then, click OK again to apply the changes to the data frame. Click Yes to close the warning.

An image of the Projected Coordinate System Properties window
Changing the central meridian is the most common parameter you can change. Some projections allow you to edit additional features.

You should immediately notice that the map rotates so that the Pacific Ocean is in the center. You have just created your first customized projection.

An image of the Mercator projection centered at 180 degrees
This image shows the Mercator projection centered at 180 degrees longitude. Click to view the image in a larger size.

Another commonly used cylindrical projection is the Transverse Mercator. Open the properties for the world map data frame. Navigate to the Coordinate System tab. Expand the Projected Coordinate Systems folder. Scroll down until you see the UTM folder. Expand the UTM folder and scroll down until you see the NAD 1983 folder. Expand the folder and choose NAD 1983 UTM Zone 10N.

An image of the Data frame properties window with UTM projection selected
The “TM” in “UTM” stands for Transverse Mercator.

When you are ready, click OK. Click Yes, when the warning appears. On the Tools toolbar, click the Full Extent button.

An image of the UTM projection for world map
The Transverse Mercator projection has a high degree of accuracy along the central meridian. Click to view the image in a larger size.

Take a moment to review the chapter text regarding the Transverse Mercator projection. When done, continue to the next step.

By default, Zone 10 is centered on Northern California. Normally, when you want to use the Transverse Mercator for a different region, you would choose the appropriate zone. However, it is possible to center the Transverse Mercator to a location manually. Using the same methods as before, create a customized Transverse Mercator projection. Change the central meridian to 57. Name the customized projection “Transverse Mercator 57.”

An image of the Transverse Mercator projection centered at 57 degrees
The Transverse Mercator is now centered on the opposite side of the globe. Click to view the image in a larger size.

Conical Projections

Conical projections transform the globe onto a flat plane using a cone as the developable surface. In this step, you will use ArcMap to explore one of the most commonly used conical projections, Lambert Conformal Conic.

Open the properties for the world map data frame. Navigate to the Coordinate System tab. Expand the Projected Coordinate Systems folder. Scroll down until you see the Continental folder. Expand the Continental folder, then expand the North America folder. Choose North America Lambert Conformal Conic. When you are ready, click OK. Click Yes, when the warning appears. On the Tools toolbar, click the Full Extent button, which looks like a globe.

An image of the Lambert Conformal Conic projection for world map
The Lambert Conformal Conic maintains the shape (conformity) of the continents, but only at mid-latitudes.

Take a moment to review the chapter text regarding the Lambert Conformal Conic projection. When done, continue to the next step.

This version of the Lambert Conformal Conic projection is centered on North America. Using the same methods as before, create a customized Lambert Conformal Conic projection centered Japan. Change the central meridian to 140. Name the customized projection “Japan Lambert Conformal Conic 140.”

An image of the Lambert Conformal Conic projection for Japan
The Lambert Conformal Conic maintains the shape (conformity) of the continents, but only at mid-latitudes. Here it is centered on Japan. Click to view the image in a larger size.

Planar Projections

Planar projections transform the globe onto a flat plane using a plane as the developable surface. In this step, you will use ArcMap to explore one of the most commonly used planar projections, the Stereographic.

Open the properties for the world map data frame. Navigate to the Coordinate System tab. Expand the Projected Coordinate Systems folder. Scroll down until you see the Polar folder. Expand the Polar folder. Choose, North Pole Stereographic. When you are ready, click OK. Click Yes, when the warning appears. On the Tools toolbar, click the Full Extent button.

An image of the Stereographic projection for world map
The Stereographic projection is conformal and commonly used for maps of polar areas and star maps. Click to view the image in a larger size.

Take a moment to review the chapter text regarding the Stereographic projection. When done, continue to the next step.

This projection is obviously centered on the North Pole. If you wanted a map centered on the South Pole, you could choose the South Pole Stereographic. However, customizing the North Pole Stereographic provides an opportunity to change a different projection parameter, the Latitude of Origin.

Using the same steps as before, open the Projected Coordinate System Properties for the North Pole Stereographic projection. Change the Latitude of Origin from 90 to -90. This step will flip the map so that it is centered on the south pole. Name the customized projection “North Pole Stereographic Flipped.”

An image of the Projected Coordinate System Properties for Stereographic
Instead of changing the central meridian as before, you change the latitude of origin.

When you are ready, click OK. Click Yes, when the warning appears. On the Tools toolbar, click the Full Extent button.

An image of the Flipped Stereographic projection for world map
Flipping the North Pole Stereographic creates the same projection as the South Pole Stereographic. Click to view the image in a larger size.

Another commonly used planar projection is the Azimuthal Equidistant. Open the properties for the world map data frame. Navigate to the Coordinate System tab. Expand the Projected Coordinate Systems folder. Scroll down until you see the Polar folder. Expand the Polar folder. Choose, South Pole Azimuthal Equidistant. When you are ready, click OK. Click Yes, when the warning appears. On the Tools toolbar, click the Full Extent button.

An image of the Azimuthal Equidistant projection for world map
The Azimuthal Equidistant projection is commonly used in world maps for aviation where the center of the map is located at a specific airport.

Though it is a planar projection and also centered on the south pole, it appears entirely different than the stereographic projection from the previous step.

Take a moment to review the chapter text regarding the Azimuthal Equidistant projection. When done, continue to the next step.

Compromise Distortion Projections

Compromise distortion projections do not try to preserve any of the map projection properties. Instead, they are designed to appear aesthetically pleasing, balancing shape and area. Using what you have learned, change the data frame projection to Robinson (world). It is located in the World folder under Projected Coordinate Systems. Change the Robinson projection so that it is centered on Humboldt County (central meridian -124). Name the customized projection “Robinson Humboldt.”

An image of the Robinson Humboldt Projection
The Robinson projection does not use any of the standard developable surfaces. Instead, this type of projection is known as a pseudocylindrical projection.

Take a moment to review the chapter text regarding compromise distortion projections. When done, continue to the next step.