Geographic Information Systems (GIS) Vocab

The vocab from my GIS class

Geographic information systems (GIS)

Computerized systems used for storing, retrieving, manipulating, analyzing, and displaying geospatial data

Geospatial technology

Various high-tech systems that process location-based data

Remote sensing

Measuring an object’s characteristics from a distance using reflected or emitted electromagnetic energy, includes satellite images and aerial photography

Global positioning system (GPS)

Uses signals from satellites in Earth’s orbit to acquire real-time location information

Geography

The study of spatial variation (how and why things differ from place to place on the surface of the Earth)

Cartography

The science and art of making maps

Datum

A reference surface of the Earth from which a coordinate system can be calculated

Geographic coordinate system

Models the Earth as a 3D object and uses latitude and longitude, measured in degrees, as its unit of measurement

Planar coordinate system

Models the Earth as a 2D surface, like a map; the units of measurement vary, but often are in meters or feet

Lines of latitude (parallels)

Run east-west and give the location of points north or south of the Equator (which is 0 degrees N/S)

Lines of longitude (meridians)

Run north-south and give the location of points east or west of the Prime Meridian (which is 0 degrees E/W)

Graticule

The latitude/longitude grid

Conformal

A projection type that preserves shapes and angles

Equivalent/equal area

A projection type that preserves area (size of objects)

Equidistant

A projection type that preserves relative distances between points on the Earth’s surface

Azimuthal (“true direction”)

A projection type that preserves direction from a central point

Compromise

A projection type that attempts to optimize Earth’s features by limiting major distortion, but by doing so, does not preserve any specific features

Developable surface

Geometric shapes which Earth’s shape is projected onto; can be conic (a cone), cylindrical, or planar (azimuthal)

Aspect

The relationship between the axis of the Earth and axis of the projection; can be equatorial (“normal”, oriented N-S), transverse (oriented E-W), oblique (neither N-S or E-W); and polar (centered on a pole)

Contact

How the surface “touches” the reference globe; determines the point of least distortion

Tangent contact

Developable surface touches the Earth along a single line or point

Secant contact

Developable surface touches the Earth at 2 lines or points

Geographic scale

The real-world size or extent of an area

Map scale

The relationship between measurements made on a map and their real-world equivalents