earth

Portraying Earth

JASON SCOTT

CHAPTER 2 MCKNIGHT ’S TEXT

Maps & Globes? Map - is a flat representation of Earth, shown reduced in size with only selected features or data showing.

Maps portray… • Distance

• Direction

• Size

• Shape in their horizontal (that is, two-dimensional) spatial relationships.

Map Scale •The scale of a map describes the relationship between distance measured on the map •Distance represented on

Earth’s surface

•Significance? •Maps are smaller than

the size of the earth

• Provides a visual & measurable

Map Scale Types •Scale Types: • Fractional map scale - conveys the

relationship between distance measured on a map

•Distance that represents on Earth with a fraction or ratio.

• Ex. 1:250,000 or 1:10,000

•Verbal map scale - the relationship between the distance on the map and the actual distance on Earth’s surface

• “one centimeter to ten kilometers” or “one-inch equals five miles.”

Large Scale & Small Scale Maps •Large Scale - relatively large representative fraction, means the denominator is small. • 1/10,000

•Visual of smaller proportion region, but attributes well defined & visible.

•Small Scale - representative fraction •One with a large denominator

• 1/10,000,000

•Visual of larger proportion of landscape, not as well defined

Map Projections •Map projection - is a system in which the spherical surface of Earth is transformed for display on a flat surface. • Imagine taking a flat

piece of paper & wrapping it around a globe...

•Accurate portrayal or no?

Families of Map Projections •Cylindrical Projection • Effect of “wrapping” the globe

with a cylinder of paper in such a way that the paper touches the globe only at the globe’s equator.

•Mercator Projection (most famous of all map projections) – • Conformal map projection

designed to facilitate oceanic navigation

Isolines • Isolines – any line that joins

points of equal value of something

• Contour lines – connects points of equal elevation on topographic maps

• Isobar – line joining points of equal atmospheric pressure

• Isotherm – line joining points of equal temperature

Global Navigation Satellite System - GNSS • Since the 1970s satellite

technology caused mapmaking to go digital

•Global Positioning System (GPS) – Created by the U.S. Dept. of Defense (1970s).

•Remote Sensing - any measurement or acquisition of information by a recording device that is not in physical contact with the object under study—in this case, Earth’s surface.

Geographic Information Systems (GIS) •GIS – computer systems designed

to analyze & display spatial data.

• Collect, store, retrieve, reorganize, analyze & map data from the real world.

•Overlay Analysis – two or more layers of data superimposed or integrated.

•GIS software has become more user friendly & accessible for everyday decision makers

•Organizations

•Governments

Aerial Photographs (Remote Sensing) •Orthophoto Maps –

multicolored, distortion-free photographic map.

•Visible Light & Infrared Sensing – wavelength radio waves, colors seen in a rainbow (human eye most sensitive to viewing)

• Thermal Infrared Sensing – sensed with conventional digital cameras. Supercooled scanners are needed

•Measures radiant temperature of objects