Ch.2 Portraying Earth

Globe

A true representation of Earth.

Maps

Flat representations of Earth that portray distance, direction, size, and shape two-dimensionally.

Thematic Maps

Maps that focus on specific themes or subjects.

Essentials for a Map

Title, date, legend, scale, direction, location, data source, and projection type.

Isoline

A line that joins data points of equal value of something on a map.

Characteristics of Isoline

Always closed lines that cannot cross each other.

Interval

Change gradient shown by spacing of isoline lines.

Elevation Contour Lines

Connect points of equal elevation on topographic maps.

Isotherms

Connect points of equal temperature.

Isobars

Connect points of equal atmospheric pressure.

Isohyet

Connect points of equal quantities of precipitation.

Isogonic Lines

Connect points of equal magnetic declination.

Map Distortions

All maps have distortions; no map can be perfectly accurate.

Map Scale

The relationship between distance measured on the map and actual distance on Earth's surface.

Graphic Scale

A line marked off in distances representing actual surface distance.

Fractional Scale

Conveyed with a fraction or ratio.

Representative Fraction

A scale expressed as a fraction.

Verbal Scale

A word scale that describes the distance relationship in words.

Large Scale

A relatively large fraction showing a small portion of Earth's surface in great detail.

Small Scale

A small representative fraction showing relatively large areas with limited detail.

Cartographer

A person who creates maps.

Map Projection

A system by which Earth's curved surface is transformed for display on a flat surface.

Equivalence

A correct size ratio of corresponding areas maintained over the entire map.

Conformality

Maintains proper angular relationships across the entire map.

Compromise Projections

Neither equivalence nor conformal; balances accurate shapes with accurate areas.

Cylindrical Projections

Wrap the globe in a cylinder tangent to the equator.

Mercator Projection

A conformal cylindrical projection designed for oceanic navigation.

Loxodrome

A line on a sphere crossing all meridians at the same angle, representing a constant compass direction.

Gnomic Projections

Obtained by projecting a globe onto a flat surface at a single point of tangency.

Orthographic Projection

A view of the Earth from space.

Conic Projections

Projecting the globe onto a cone wrapped around a portion of the surface.

Pseudocylindrical Projections

A mix of conformal and equivalent, near football-shaped maps.

Goode’s Interrupted Homolosine Projection

An equivalent projection that maintains shapes of continental coastlines.

Digital Elevation Model

Computer-generated images derived from precise elevations compiled in detailed databases.

Global Navigation Satellite System

A system of satellite technologies providing precise location data.

GPS

Global Positioning System in the US.

GLONASS

Russia’s global navigation satellite system.

Galileo

Europe’s global navigation satellite system.

Beidou

China’s global navigation satellite system.

Triangulation

A method for calculating three-dimensional coordinates.

Wide Area Augmentation System (WAAS)

A network of ground-based reference stations for GPS signal correction.

Continuously Operating GPS Reference Station (CORS)

A system of permanent GPS receiving stations managed by NOAA.

GPS Modernization Program

Newer satellites with greater accuracy and civilian broadcast signals.

Remote Sensing

Measurement by a device not in contact with Earth’s surface.

Aerial Photographs

Photographs taken from the air for mapping purposes.

Photogrammetry

The science of making measurements from photographs.

Orthophoto Maps

Distortion-free photographic maps prepared from aerial photographs.

Visible Light and Infrared Sensing

Utilizing wavelengths of electromagnetic radiation for sensing.

Color Infrared

Uses sensors to detect near-infrared wavelengths, showing vegetation in red.

Thermal Infrared

Measures radiant temperature and yields photographic-like images.

Multispectral Remote Sensing

Detects and records many bands of the electromagnetic spectrum.

Landsat

A series of satellites originated at NASA for Earth observation.

Earth Observing System

Satellites like Terra and Aqua that collect a range of data values.

Commercial High-Resolution Satellites

Small, lower-cost satellites providing very high-resolution imagery.

Radar

A system using radio waves for detection and ranging.

Sonar

Sound navigation and ranging technology.

Lidar

Uses reflected laser light to measure distance.

Geographic Information System (GIS)

Computer systems designed