” Raster is vaster, but raster is faster
and vector just seems correcter.”
The term Geographical Information System (GIS) generally refers to a computer system which allows to obtain geographical information. This technology is very powerful in collecting and processing several aspects of the landscape.
The concept of GIS has originally derived from the experience matured over the years in several fields and disciplines involved in territorial studies, like design and cadastral mapping, aerial photography, geographical and geological mapping, remote sensing, urban and rural planning, and analysis of spatial data.
In the context of these applications, issues have been addressed related to the acquisition, processing and application of spatial data. It is within these functions that GIS operates, able to provide a level of information that improves the understanding of the phenomena and processes, thus increasing our capacity of analysis and actions on issues concerning the landscape.
In the initial phases, vector and raster data and operations were still strictly separated. But things have largely evolved after I made the first raster GIS elaboration of the Province of Rome in 1983-4 and organized a GIS course in Rome for the SIGEA in 1994.
Map algebra as developed by Tomlin was incorporated in the raster MAP package (later MAP2), which in the late 1980s evolved further into the “GeoPackage” program (Geops BV, Wageningen), by adding digitize and presentation facilities, and raster – vector conversion.
Raster & vector formats are now usable and convertible in many programs, but Map algebra still forms the basis of most raster operations.
Map algebra is a simple and an elegant set-based algebra for manipulating geographic data, proposed by Dana Tomlin in the early 1980s. It is a set of primitive operations in a geographic information system (GIS) which allows two or more raster layers (“maps”) of similar dimensions to produce a new raster layer (map) using algebraic operations such as addition, subtraction etc.
Depending on the spatial neighborhood, GIS transformations are categorized into four classes: local, focal, global, and zonal. Local operations works on individual raster cells, or pixels. Focal operations work on cells and their neighbors, whereas global operations work on the entire layer. Finally, zonal operations work on areas of cells that share the same value. The input and output for each operator being map, the operators can be combined into a procedure, script, to perform complex tasks (info Wikipedia).
The latest GIS development is that you don’t even have to copy the various base maps to your computer, but can consult them directly on your software through the WMS (Web Map Service), already made available in some regions of Italy.
At the moment, for a start and beyond, I would recommend as GIS software the Open Source QuantumGIS (QGis), now at version 1.8: easy to use, quickly improving, good vector and raster handling and conversion; raster calculator and more processing tools; although some operations and the graphic output could still improve quite a lot.
For a basic understanding of GIS principles, I recommend the book by Peter Burrough and Rachael A. McDonnell, 1998 – Principles of Geographic Information Systems, 2nd Ed., Oxford University Press.
Book description by Amazon:
This book is a completely new version of the highly successful Principles of Geographical Information Systems for Land Resources Assessment which was first published in 1986. GIS are not just used for electronic map-making but today are major tools for the management of our physical and social environment. GIS are used to assist political decisions and play a part in market research, in the management of utility services, in automated navigation systems and in many other fields. This book presents a strong theoretical basis for GIS, which is often lacking in other texts. Spatial data are usually based on two, dichotomous paradigms, exactly defined entities in space, such as land parcels, or the continuous variation of single attributes, such as temperature or rainfall. Methods for modelling both kinds of phenomena and storing them in spatial databases are described in detail, including the use of geostatistics for interpolating from points to continuous fields. Examples of how spatial data and an analysis of their spatial interactions are used to solve a wide range of practical problems ranging from site-location analysis through land degradation, the optimizing of timber extraction from forests and the redistribution of Chernobyl radioactivity by floods are explained clearly and in detail. Much attention is paid to the problems of data quality and how statistical errors in spatial data can affect the results of spatial modelling based on the two paradigms of space. Fuzzy logic and continuous classification methods are presented as methods for linking the two spatial paradigms. The book concludes with an investigation of current developments in providing spatial data for the whole world over the Internet. As such the new volume provides a comprehensive and concise introduction to the theory and practice of Geographical Information Systems (GIS). Targeted at undergraduates, graduates, and professionals in disciplines such as physical and human geography, hydrology, geology, environmental science, cartography, epidemiology, radioecology, agriculture, spatial planning, land tenure, and land evaluation the book explains why spatial data and the information systems based on them are important in the modern world.