GEOGRAPHIC INFORMATION SYSTEMS
Learning outcomes of the course unit
The course aims to: make known the territorial information systems showing their usefulness in concrete applications of environmental and territorial nature, to develop the student's ability to apply an engineering approach to problem solving. To this end, approximately 50% of the teaching hours are spent on laboratory activities.
Specifically at the end of the activities the student is asked to provide proof of:
- know the characteristics and peculiarities of spatial data, including acquisition techniques and their tolerances, with particular reference to Digital Land Models and Orthophotos;
- know the geodetic-cartographic reference systems (SdR), in which these data are expressed and what are the limits of use of the transformation parameters stored in the GIS;
- know how to associate the SdR and/or the cartographic representation to the data;
- know how to import, export and convert data in raster and vector format between SdR and different cartographic projections;
- know the characteristics of the vector and raster data structures and the information needed for their georeferencing;
- know the techniques of spatial interpolation and georeferencing of raster data;
- know the basic concepts of databases and their query;
- be able to conduct spatial and attribute queries using the search tools implemented in GIS;
- be able to schematize a problem and identify the most appropriate GIS tools to solve it;
- know a significant spectrum of basic GIS applications in civil and environmental engineering.
Basic concepts of cartography, geodetic datums, statistical data
processing and analysis, computer literacy.
Course contents summary
Geographic Information Systems (GIS) or SIT (Territorial Information Systems) are IT tools capable of managing and crossing the great variety of information sources and types of data that must be considered in the decision-making and management processes in the governance of the territory. They allow the import, processing, storage and representation of spatial data of various kinds.
The entities stored in a SIT, in addition to the specific information to be processed, have always associated the geographical position, so the SIT have the ability to manage data provided in different geodetic / cartographic reference systems and carry out searches and selections based on relationships of spatial proximity, as well as thematic queries.
The course presents the characteristics of spatial data in digital format and the techniques for processing them in SIT.
To this end, the fundamental concepts of geodetic reference system and cartographic representation are referred to.
The main data acquisition techniques for SITs and their characteristics and accuracy are then illustrated.
Then we introduce the raster and vectorial data, paying particular attention to Digital Terrestrial Models (DTM) and orthophotos.
Then there is the structure of Numerical Cartography and its evolution into topographical DBs. Finally, SITs are first introduced with an operational approach that favours the ability to use the various types of functions for importing, selecting, searching and processing raster and vectorial data. Subsequently, the phases of the design of a SIT are mentioned, in particular the definition of conceptual and logical models. Finally, the databases at municipal, regional and national level are reviewed.
In the laboratory exercises, this knowledge is then applied to a series of practical cases, taken from engineering issues, on the QGIS open source platform.
Geodesy: geodetic datum definition. Coordinate transformations. Transformations between reference systems.
Cartography: conformal and equivalent maps; map contents and map generalization; tolerances; italian topographic and technical maps.
Information on data acquisition techniques and technologies for Digital Terrestrial Models, orthophotos, Digital Maps and Geographical Information Systems.
The Digital Terrain Models (DTM). Components of a DTM. Interpolation methods. TIN and GRID data structures. Operations on the DTMs. Testing of the DTMs.
Digital orthophotos. Advantages and disadvantages compared to numerical mapping. Generation of orthophotos. Testing of orthophotos. Digital maps: definitions and differences with respect to traditional maps.
Contents of digital maps. Information coding.
Raster data: spatial and radiometric resolution. Raster data acquisition.
Rasterization of maps; georeferencing and mosaicking.
Vector data: geometric and topologic primitives. Vector data acquisition.
Cartographic editing and consistency checks.
Geographic information systems: fundamental components and
Metadata. Manipulation of raster and vector data: queries; processing of raster data; visualization and representation of results.
Use of software for DTM generation (Surfer): comparisons between interpolation methods, residuals calculation, visualization methods, terrain profile extraction, multi-temporal comparisons, volume calculation.
Presentation and use of the QGIS open-source sw: data import, definition of the SdR, data export, editing operations on geometry and attributes of vectorial data. Queries, joinings and spatial and tabular selections. Calculation of field statistics. Georeferencing of raster data. Using the raster computer. Vector and raster data processing in environmental engineering applications.
C. Jones. Geographic Information Systems and Computer Cartography,
Prentice Hall. – Not available at the “Biblioteca politecnica di Ingegneria e Architettura”.
Course material (slides of the lectures, exercices, sample data etc.) can be found at SISTEMI INFORMATIVI TERRITORIALI, available online on the Uni e-learning platform. Registration to the course
All the material is usually available at the beginning of the course, but it is also updated during the lessons, especially as regards the data to be used in the exercises.
The course is divided into a first part dedicated to DTMs and orthophotos in which frontal lessons of theory and laboratory exercises alternate. This is followed by a part mainly devoted to completing the theoretical foundations of GIS. The last part of the course is then held entirely in the laboratory. Overall, the proportion of hours of lecture and workshop practice is about 1:1.
The introduction to the different sw and functions available in each is guided by simple examples. Once the fundamental tools have been acquired, the teacher presents a problem (clarifying the objectives and the available data) and the students are invited to propose a solution strategy, discussing the alternatives in a group and then working autonomously to implement them.
Assessment methods and criteria
Oral interview with questions about the theoretical contents, followed by simple exercises of
processing, displaying, querying data to the computer via programs
Surfer and QGIS.
The questions count for about 60% of the score and verify the theoretical-methodological knowledge base, the processing exercises with software for the remaining 40% and verify the ability to apply knowledge and self-learning ability. The list of skills required to use the software (indispensable for passing the exam) is available on the teaching material website.