GPS and GIS Flashcards

Flashcards on Global Positioning System (GPS) and Geographic Information System (GIS)

Global Positioning System (GPS)

Emerged during the 1970s, growing out of space programs and funded by the military for global navigation and guidance.

Global Navigation Satellite Systems (GNSS)

The entire scope of satellite systems used in positioning.

Receiver Position Computation in GPS

Precise distances from satellites to receivers are determined from timing and signal information to compute receiver positions.

Satellite Surveying

Satellites act as reference or control stations, and the distances to these satellites are used to calculate the receiver positions.

Three Parts of the Global Positioning System

The space segment, the control segment, and the user segment.

Space Segment

Consists nominally of 24 satellites operating in six orbital planes spaced at 60° intervals around the equator, with four additional satellites as spares.

Control Segment

Consists of monitoring stations that track the positions and monitor the signals of the satellites over time.

User Segment Services

Standard Position Service (SPS) and Precise Positioning Service (PPS).

Geocentric Coordinate System

Uses a three-dimensional Cartesian coordinate system with the Earth's center as the origin.

Geodetic Coordinate System

Uses latitude and longitude, which are defined relative to a reference ellipsoid and the local vertical.

Geographic Information System (GIS)

Any information management system that can collect, store, and retrieve information based on its spatial location.

Examples of GIS Layers

Parcels of landownership, zoning, floodplains, wetlands, land cover, and soil types.

Geodetic Reference Framework

A network of survey control points in the area, providing spatial location for all data in a common reference system.

Composite Maps (GIS)

Merging two or more different data sets.

Points (Spatial elements in GIS)

Single geometric locations used to locate features such as houses, wells, mines, or bridges.

Lines and Strings (Spatial elements in GIS)

Obtained by connecting points, used to represent roads, streams, fences, property lines, etc.

Interior Areas (Spatial elements in GIS)

Continuous space within three or more connected lines forming a closed loop, used to represent governmental jurisdictions, landownership, etc.

Pixels (Spatial elements in GIS)

Tiny squares that represent the smallest elements into which a digital image is divided.

Grid Cells (Spatial elements in GIS)

Single elements, usually square, within a continuous geographic variable, used to represent slopes, soil types, etc.

Vector Format (Data models of GIS)

A combination of points, lines, strings, and interior areas is used.

Raster Format (Data models of GIS)

Pixels and grid cells are used.

Predominant Coding

Each grid cell is assigned the value corresponding to the predominant characteristic of the area it covers.

Precedence Coding

Each category in the vector data is ranked according to its importance with respect to the other categories.

Center-Point Coding

A cell is assigned the category value at the vector location corresponding to its center point.