Geographic Information Systems (GM/LA 282) Practice Flashcards

A complete set of vocabulary flashcards derived from the GM/LA 282 lecture notes on Geographic Information Systems, covering historical foundations, data models, spatial analysis, and technical procedures.

Geographic Information Systems (GIS)

A computerized system for managing digital data that has coordinates ($x, y, z$ location) and provides means to link scientific 이해 to digital maps for resource management.

Dr. John Snow

An English Physician who, in 1854, performed the first documented GIS analysis by plotting cholera cases on a map of London to relate spatial and non-spatial data.

Free Open Source Software (FOSS)

GIS software distributed free of charge that can be modified to suit user needs, developed often by organizations to reduce licensing costs.

Geospatial Data

Any digital data that has coordinates ($x, y, z$ location); also referred to as geo-referenced data.

Toolbox Definitions of GIS

Definitions that describe GIS as a powerful set of tools for capturing, storing, retrieving, transforming, and displaying data from the real world.

GIS Components

The five primary elements required for GIS: hardware, appropriate software, organizational context (skilled personnel and procedures), and networks.

Data Transformation

A GIS function involving stages to remove errors, match data, or perform analysis such as calculating quantities, changing projections, or changing map scales.

Points

The most fundamental spatial geometric primitive without any extension, used to represent features such as wells, survey pillars, or electric poles.

Lines

One-dimensional objects used to represent linear features such as roads, rivers, contours, and powerlines.

Polygons

Geometric primitives used to represent area features or surfaces, such as lakes, buildings, farms, or land uses.

Continuous Surfaces

A concept applied to represent objects that occur continuously in space and time without definite boundaries, such as topography, temperature, or precipitation.

Attributes

Data which describe objects but have no spatial structure or location information, such as ownership names, material types, or cost.

Nominal Attribute

A classification that distinguishes between locations without ranking or arithmetic potential, such as telephone numbers or land use class IDs.

Ordinal Attribute

A classification that implies a ranking (e.g., Class 1 is better than Class 2), though arithmetic operations do not make sense.

Interval Attribute

Attributes where differences between measurements are meaningful, such as Celsius or Fahrenheit temperature scales or elevation above sea level.

Ratio Attribute

Attributes where it makes sense to divide one measurement by another, characterized by an absolute zero and the absence of negative values.

Cyclic Attribute

Measurements representing directions or cyclic phenomena where distinct points like $0^\text{o}$ and $360^\text{o}$ can be equal.

Vector Data Model

A spatial model that represents reality through points, lines, and polygons, storing accurate coordinates and discrete boundaries.

Sliver Polygons

Small polygons along shared boundaries created when the edges of two polygons do not meet properly during overlay or digitizing.

Undershoots

An error in vector data quality where a line feature does not meet another line feature of the same kind at an intersection.

Overshoots

An error in vector data quality where a line feature crosses and extends beyond another line feature it should connect to.

Raster Data Model

A model representing phenomena as a series of grids or cells in columns and rows, ideal for continuously varying data like topography.

Rasterization

The GIS process of converting vector data into the raster data format.

Vectorization

The GIS process of converting raster data into the vector data format.

Euclidean Distance

The straight-line distance computed based on Cartesian coordinates using the formula $d = \text{SQRT}((x_2 - x_1)^2 + (y_2 - y_1)^2)$.

Spherical Distance

Long distances on the surface of the Earth computed through spherical trigonometry using angular distance ($\text{psi}$) and the mean radius of Earth ($R$).

Overlay

A GIS operation that places one map layer on top of another to create a third map, modifying original features or their attributes.

Point-in-Polygon

An overlay operation where point data is combined with polygon data to determine, for example, which district a specific well is located in.

Map Algebra

The use of mathematical operators ($+$, $-$, $/$, $\times$) or logical operators (AND, OR, NOT) to combine different raster layers.

Interpolation

The procedure for estimating unknown quantities at unsampled sites using known quantities from neighboring locations.

Buffering

The process of creating one or more zones around a feature at a specified linear Euclidean distance, resulting in polygon features.

Connectivity (Topology)

A topological rule stating that arcs connect to each other at points known as nodes.

Arc

In topological terminology, a line segment connected to two endpoints; it includes a starting from-Node and an ending to-Node.

Planar Network

A network where all junctions (e.g., roundabouts or T-junctions) are on the same plane and nodes exist at every intersection.

Non-planar Network

A network where junctions are on different planes, such as overpasses or flyovers, meaning no nodes are allowed at the crossings.

Hybrid Database System

A GIS database system where geometric data and attribute data are stored in separate databases.

Normalization

The process of decomposing a database table into its simplest form to avoid redundancy and facilitate separate updates.

Attribute Data Query

A method of retrieving information from GIS data using expressions, often written in SQL (Structured Query Language).

Manual Digitizing

A technique converting paper maps to digital format using a digitizing surface and a hand-held cursor to trace features.

GPS Space Segment

The part of the Global Positioning System consisting of 24 satellites orbiting at an altitude of $202001,km$ above the Earth.

UTM WGS84 Projection

The Universal Transverse Mercator coordinate system and datum adopted for use by many countries, including Ghana, for modern mapping.