| Term | Definition |
|---|
| Georeferences | the act of assigning locations to atoms of information |
| Metric georeferences | georeferences based on various kinds of measurements (longitude & latitude, coordinate systems) |
| Placenames | limited use as georeferences, meaning can be lost through time |
| UTM | Universal Transverse Mercator |
| USPLSS | US Public Land Survey System (metric georeferencing) |
| Prime Meridian | an accurate north-south line |
| Latitude | the location of a place on Earth north or south of the equator (angular measurement in 0 - 90 degrees) |
| Longitude | the location of a place on Earth east or west of a north-south line called the Prime Meridian (angular measurement in -180 to 0 to 180 degrees) |
| Cylindrical projections | analogous to wrapping a cylinder of paper around the Earth, projecting the Earth's feaetures onto and then unwrapping the cylinder |
| Azimuthal projections | analogous to touching the Earth with a sheet of paper |
| Conic projections | analogous to wrapping a sheet of paper around the Earth in a cone |
| Projection | detail lost and distortions happen when Earth is flattened |
| Conformal property | ensures that the shapes of small features on the Earth's surface are preserved on the projection, the the scales of the projecton in the x and y directions are always equal |
| Equal area property | ensures that areas measured on the map are always in the same proportion to areas measured on the Earth's surface |
| Graticule | when the lines of latitude and longitude map onto the projection in a distorted grid |
| Uncertainty | problems that arise out of imperfect GIIS-based representaions of the real world |
| Measurement error | differences between observers or between measuring instruments (omission of road accessibility or omitting employment status) |
| Accuracy | difference between reality and our representation of reality |
| Direct indicators | bear a clear correspondence with a mapped phenomenon (ie detailed household income figures) |
| Indirect indicators | used when the best available measure is a perceived surrogate link with the phenomenon of interest (incidence of central heating amongst households or rates of multiple car ownership) |
| Error propagation | measures the impacts of uncertainty in data on the results of GIS operatons |
| Ecological fallacy | inappropriate inference from aggregate data about the characteristics of individuals (ie: chinese, shoe factory, unemployment rate) |
| COTS | Commercial off the shelf |
| Shareware | usually intended for sale after a trial period |
| Liteware | shareware with some capabilities disabled |
| Freeware | free software but with copyright restrictions |
| Public domain software | free with no restrictions |
| Open source software | the source code is provide and users agree to limit the distribution of improvements |
| GUI | graphical user interfaces (menu-driven, simiplified user interaction) |
| Three-tier architecture | from the information systems perspective, GIS has three key parts: the user interface, the tools, and the data management system |
| LAN | Local Area Network |
| WAN | Wide Area Network |
| Desktop GIS | three software tiers are all installed on a single piece of hardware |
| Centralized desktop GIS | data files are held on a centralized file server but the data server functionalit is still part of the desktop GIS |
| Client-server | users interact with a desktop GIS GUI on their desktop but the database management software and data may be located on another machine connected over a network |
| Centralized server | all GUI and business logic is hosted on application server, users on remote machines access software over LAN o WAN |
| Data model | a set of constructs for describing and representing parts of the real world in a digital computer system |
| Layer | a collection of entities of the same geometric type (dimensionality) |
| CAD data model | real-world entities are represented symbolically as simpe point, line and polygon vectors |
| Graphical data model | simple mapping (non-topological) |
| Image data model | Image processing and simple grid analysis |
| Raster/Grid data model | uses an array of cells or pixels, to represent real-world objects (field conceptual data model) |
| Vector/Georelational topological data model | each object in the real world is first classified into a geometric type (discrete object view) |
| Network data model | special type of topological feature model (model the flow of goods and services) |
| Object data model | collection of geographic objects and the relationships between the objects |
| Object | a self-contained package of information describing the characteristics and capabilties of an entity under study |
| Class | a template for objects |
| Encapsulation | each object packages together a description of its state and behavior |
| UML | Unified Modeling Language |
| CASE | computer-aided software engineering tool, a software application that has graphical tools to draw and specify a logical model |
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