Mapping the Globe Flashcards
What is a Geoid?
-The irregular shape of the Earth’s surface under the influence of gravity and rotation
-Simplified to a sphere (small-scale maps) or spheroid (large-scale maps).
What are the types of Spheroids (Ellipsoids)?
-Oblate: wide
-Prolate: tall
What is a Geographic Coordinate System?
-A three-dimensional spherical surface to define locations on the earth.
-Locations are measured using angles from the earth’s center to a point on the earth’s surface.
What is a Projected Coordinate System?
-Defined on a flat, two-dimensional surface.
-Based on a geographic coordinate system that is based on a sphere or spheroid.
What is a Datum?
Defines the position of the spheroid relative to the center of the earth. It defines the origin and orientation of latitude and longitude lines.
What are the Projected Coordinate System Distortions?
Shape, Area, Distance, Direction
What are the Projection Types?
-Conformal: preserves shape
-Equivalent: preserves area
-Equidistant: preserves distance
-Azimuthal: preserves direction
What are the Projection Surfaces?
Cylindrical, Conic, Planar
What is a Spatial Reference Identifier (SRID)?
Created by the Open Geospatial Consortium to uniquely identify a coordinate system (e.g., 4269).
What is Well-Known Text (WKT)?
Unique name for each coordinate system (e.g., NAD83)
What is the preferred spheroid in the US?
GRS 1980
What is the preferred spheroid of the world?/What is the spheroid used by GPS?
WGS84
What is the approximate center of the US?
Meade’s Ranch Triangulation Station, Kansas
What is the North American Datum Conversion Software (NADCON)?
Used for Datum Transformations. Converts Nad27 to NAD83 and vice versa.
What is a Datum Shift?
The difference in coordinates between datums
