Basic Analysis and Graphing - SAS

420 Creating Maps Chapter 16
Background Maps
Images
Every flat map misrepresents the surface of the Earth in some way. Maps cannot match a globe in truly
representing the surface of the entire Earth. A map projection is used to portray all or part of the round
Earth on a flat surface. This cannot be done without some distortion. Every projection has its own set of
advantages and disadvantages. A map can show one or more, but not all, of the following: true direction,
distance, area, or shape. JMP employs a couple of projections (Albers Equal Area Conic and Kavrayskiy VII)
for its maps. Within Images, you can choose from two built-in map images, or you can connect to a Web
Map Service to retrieve a background image.
Earth Images Installed with JMP
JMP provides two levels of earth imagery; simple and detailed. Both maps show features such as bodies of
water and terrain. However, detailed maps show more precise terrain. And with detailed maps, you can
zoom in farther, and the map features remain clear. Image maps are raster images. The maps wrap
horizontally, so you continue to see map details as you scroll from left to right. The maps do not wrap
vertically. Beyond the -90 and 90 y-axis range, a plain background appears instead of the map.
Figure 16.14 Examples of Simple and Detailed Maps
Simple Earth Image
Detailed Earth Image
As its name suggests, Simple Earth is a relatively unadorned image of the earth’s geography. It does not show
clouds or arctic ice, and it uses a green and brown color scheme for the land and a constant deep blue for
water. Detailed Earth has a softer color scheme than Simple Earth, lighter greens and browns for the land, as
well as variation in the blue for the water. Detailed Earth also has a slightly higher resolution than Simple
Earth. The higher resolution lets you zoom into a graph further with Detailed Earth than with Simple Earth
before the quality of the background image begins to blur.
Another feature of Simple Earth and Detailed Earth is the ability to wrap. The Earth is round, and when
you cross 180° longitude, the Earth does not end. The longitudinal value continues from -180° and
increases. The map wraps continuously in the horizontal direction, much as the Earth does. The
background map does not wrap in the vertical direction.
Simple Earth and Detailed Earth both support a geodesic scaling. In Figure 16.14 on page 420, the Earth
appears as a rectangle, where the width is twice as wide as the height. If we were to take this rectangle and
roll it up, we would have a cylinder. In reality, we know that the Earth does not form a cylinder, but rather a