Summary
Summary Geomatics Second Year First Semester
- Institution
- University Of Cape Town (UCT)
Includes everything mentioned in Year 2 Geomatics Lectures, and notes. Extremely detailed.
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Chapter 1: IntroductionWhat is GIS? A Geographic Information System (GIS) is a system of hardware, software and procedures designed to support the capture, management, manipulation, analysis, modelling
and display of spatially – referenced data for solving complex planning and management problems.
GIS History
• GIS in digital form have been around since the 1960’s.
• GIS developed with the development of maps which generalize the earth’s surface and provide information for various types of analysis.
• Records of the Babylonian land rights mapped in clay tablets are the oldest known maps in existence and date back to 2300 BC.
• Cadastral Maps, or maps of property rights, were also recorded in the Nile Valley by ancient Egyptians.
• For the Egyptians, it was necessary to record and demarcate agricultural allotments in the valley every year due to annual seasonal flooding.
• In early 1800’s, Napoleon implemented a Cadastral system based on classifications of land use in France for land taxation purposes in the aftermath of the French Revolution and the demise
of the feudal system of land tenure.
• Manual GIS systems evolved from the discipline of cartography.
Any GIS is an integration of 5 basic components:
• People: Most important component of a GIS.
People must develop the procedures and define the tasks of the GIS.
People can overcome shortcomings in other components of the GIS, but the best GIS software and hardware cannot compensate for people’s incompetence.
• Data: The availability and cost of data has a huge impact on the success of a GIS project.
Data is the basis upon which all later analysis and subsequent decision-making is based, hence data accuracy and integrity need to be properly assessed.
• Hardware: Hardware capabilities affect processing speed, ease of use, and the type of output available.
• Software: This includes not only actual GIS software, but also database drawing, statistical, imaging and other software that might be utilized.
• Analysis / procedures: Analysis requires well-defined, consistent procedures to produce accurate, reproducible results.
Modelling is common for an analysis of GIS.
GIS Functions
• Planning: Includes digitizing or scanning, layer identification, organizing, and decision-making.
• Data Capture: Geographic (spatial) and attribute (non-spatial) data can be captured by various methods. E.g. digitizing, scanning, importing, manual data entering, etc.
• Data Storage and Management: GIS are useful for storing and managing spatially related datasets in a spatial database. There are 2 data models: raster & vector.
• Data Manipulation / Editing: Cleaning and editing of data (e.g. addresses), edge-matching, adjacent sheets, layering, georeferencing.
• Data Display: Visualization tools that can display geographic and attribute data using a variety of symbology.
• Data Analysis: Spatial and attribute query, buffering / proximity analysis, network analysis, overlay analysis, 3D simulation.
• Modelling: Multi-criterial analysis, multiple query, simulation, forecasting, scenario building.
• Data Output: Communicating the solution to the problem via tables, maps, reports, graphs, etc.
, Benefits to using GIS:
• Presentation Capabilities: Presenting Data in a more exciting and spatially relevant way.
• Geographic Search: Asking questions about the location of data.
• Spatial Analysis: Creating ‘new’ data via operations such as overlay.
Distance Calculations.
Buffer Zones around features.
• Data Integration: Storing & managing a diverse range of geographically based datasets (a spatial library).
Reliable and consistent data management.
• Modelling: Aids in understanding phenomena and in predicting the outcomes of similar events. E.g. wild fires.
• Visualization: Assessing the impact of new developments.
Environmental impact assessments.
3D applications.
• Other Benefits: Time saving.
Optimizing costs through process automation.
Project Monitoring.
Decision Support.
Accuracy Improvement.
Typical Challenges Associated with GIS:
Cost: Costs of hardware and software rarely exceed 20% of the total system cost.
Software maintenance and upgrade fees quickly exceed initial cost.
Database development makes a large component of the total system cost.
Biggest cost of a GIS = Data capture costs.
Responsibility: Privacy: GIS technology can be used to build detailed information databases on individual citizens, thus threatening individual privacy.
Decision Making: GIS can be used to make reliable decisions based on good data or unreliable decisions based on bad data or inappropriate methods of analysis.
Uncertainty: A discrete data model does not always suit reality.
Difficulties arise in depicting phenomena that lack clear physical demarcation, such as soil types, population densities, or prevailing temperatures.
Conceptual Generalization: When points, lines, and polygons are selected as the geometric representation of objects, this results in a generalization of the real world.
Need to divide objects into classes also results in a generalization.
E.g. An area of forest that is mainly coniferous, with some deciduous, will often be generalized and classified as coniferous, not as a combination.
Workplace: Reliance on technology increases the vulnerability of businesses to power, hardware and software failures, as well as changes to hardware and software.
GIS is a specialized field requiring a skilled workforce, something that is difficult to acquire and maintain.
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