Data are facts and figures that are collected, managed and used in most fields of human endeavour; we therefore often hear about population data, rainfall data, employee data, etc. Data that are referenced to a spatial location in geographic space are known as geospatial data; so, data about a road, a forest, an air route, etc are all geospatial since the features concerned are all geographical. Other data are said to be non-spatial, for example data about people's salaries, stock market shares, etc. Information is what results from processing data; for example the coordinates defining the boundary of a land parcel, which are of little interest to the land owner, can be processed into the parcel's area, which is of much meaning to the said owner. An information system is one in which data is input and processed and information is output. Many people are familiar with management information systems that deal with non-spatial data and are used for general administration and business; a good example is the student management information system at the university.
A geographic information system is a computer based information system that enables the input, management (storage, retrieval, updating), analysis, output and dissemination of geospatial data and information. As shown in Figure 1, it consists of computer hardware, appropriate software, data, organizational procedures and people. Data is the greatest asset in any GIS, and consists of geographic feature positions in a coordinate system, attributes and relationships, all kept in an integrated and structured database, which is managed by a database management system (DBMS).
Feature positions describe where a feature is, e.g. the Cartesian coordinates that define a road centerline; feature attributes define what a feature is, e.g. the fact that the road is tarmac, or that it is one way; feature student engineer.indd 19 21/03/2016 4:53 PM 20 The Student Engineer relationships describe how a feature is related to other features, e.g. the fact that a road is connected to another road, or that a factory is within a given land parcel. Construction of a GIS database often takes up more than 70% of the costs in setting up the system. Common GIS software include the industry flagship ARCGIS and the open source QGIS.
Engineering may be most generally defined as the application of mathematical and scientific principles to design, construct and maintain a product. That product may be minute, such as a computer microchip, or massive, such as a high rise building or a highway; the product may be highly visible, such as the Eiffel tower in Paris, but it could also be invisible and intangible, e.g. a computer database. In relation to the latter case, the field of Surveying has been known as geospatial engineering since the late 1990s when all the work involved in all aspects of surveying merged into the design, construction and maintenance of a geospatial database. GIS is now one of the key fields of study in geospatial engineering and many geospatial engineering graduates can be found in GIS practice.
Considering that over 80% of all data are geospatial, GIS as a decision making tool is applied in many diverse areas, including engineering; the only things required are appropriate data and analysis functions. Applications of GIS can be found at all scales ranging from the very local (e.g. precision farming, in which fertilizer application and planting patterns are correlated to previous yields and soil fertility levels) through regional (e.g. determining the best areas in which to grow coffee) to global (e.g. monitoring the worldwide destruction of forests or spread of HIV/ AIDS). The key strength of GIS is its ability to overlay and perform integrated analysis of diverse datasets, enabling quick answers to questions such as "what is at a given location ?", e.g. what is the soil type at a given location along a proposed road corridor?; "where is a given feature?", e.g. show all sewer lines with a diameter of more than 0.25 m; "what is the length, area or volume of a given feature?" e.g. the length of a road, area of a lake, volume of a reservoir; "is a given feature changing, and if so, how?" e.g. in monitoring the rate of deforestation; "what if a certain scenario were to happen (modeling)?" e.g. were a flood to occur, which settlements would be affected and where could they be evacuated to? Specifically, in engineering, some typical applications of GIS include, but are not limited to:
- Civil engineering - site location (e.g.
road or railway route location), works
- Mechanical engineering - spatial location of diverse facilities, e.g. factories and wind farms; pollution monitoring.
- Electrical engineering - spatial location of and monitoring spatial distribution of power line routes, plus associated facilities such as transformers, sub-stations, etc
- Environmental and Bio-systems engineering
- design of irrigation schemes, precision farming, location of waste disposal sites, etc
- Geospatial engineering - design, construction and maintenance of diverse mapping products, including terrain and surface models.
In 1998, Kenya's urban roads were in urgent need of maintenance following devastating El Nino rains. It was soon realized , however, that the only information available on the country's urban roads was in analogue form, kept by diverse agencies (e.g. Ministry of Public Works, Survey of Kenya, city and municipal councils, etc), often on different coordinate systems and of doubtful accuracy. The proposed maintenance works could therefore not be effectively planned using this poor information base, since it was impossible to identify which sections of road needed maintenance and the kind of maintenance required. The Kenya Urban Transport Infrastructure Project (KUTIP) was then set up with the objective of mapping the roads, collecting road condition data and integrating all in a GIS database. The project targeted a total of about 12000 Km or road in the CBDs of 26 towns. The roads were subsequently digitally mapped largely through large scale photogrammetry, and road condition data (kept general as good, fair, poor and bad) were collected using total stations or GNSS, and the mapping and road condition data were integrated into a GIS database. Figure 2 and Table 1 show abstracts from the database for Kakamega roads.
WOnce the GIS was set up, it became much easier and faster for the KUTIP engineers, financiers, town councilors and other interested parties to visualize the scope of the proposed works and to draw up an emergency road maintenance budget for each town. For example, in the digital map, roads could be highlighted in different colours, each colour indicating a different condition and the corresponding maintenance action needed. This was very effective for communicating the scope of the project to lay people like councilors who were keen to see that roads in their electoral areas were considered. For budget estimation, a simple computer program designed to extract data from the attribute table would be able to multiply the readily available length of any road section by the cost per Km of the required resealing, overlaying or reconstruction (as the case may be) and in no time generate a print out of the maintenance cost per road per town and for the whole project. This would take ages using traditional manual methods, resulting in delayed decision making, quite undesirable in an emergency situation.
Through the use of GIS, the roads in most of the towns were quickly restored and economic activity and delivery of services restored. In addition, the GIS remained in place, meaning that it should have been much easier to keep the road maps and attributes up to date, so that should another El Nino happen, the towns would be much better prepared to deal with the emergency. This is a good demonstration of the power of GIS in an engineering application.
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