The present geographical information system GILES was developed particularly for the assessment of the potential of the land for agriculture and its need for conservation measures to sustain agricultural productivity in developing countries and additionally to establish a land resource database.
There was a pronounced need of a computerized, fast, flexible system, capable of a high level of detail, for multipurpose map retrieval and overlay to fulfill above mentioned requirements.
This led to the development of GILES: GILES now presents an interactive, grid-cell based, low-cost, easy-to-handle GIS system with strong emphasis on map overlay, particularly for agricultural planning purposes, for the output of raster or plot maps and transfer of maps and statistics via translation files into other software systems. Printer for various scales outprint, plotter and digitizing tablet are supported, less attention is given in the present version to automated cartography. It runs on any 'compatible' micro-computer with DOS system and with a harddisk. GILES is completely menu-driven and supported by help menus; queries by users will be responded immediately.
GILES as any GIS is scale independent (see App.10 for areas and scales in Ethiopia where GILES is applied; p.257). But main advantage of GILES is the answer for improvement and sustaining of agricultural productivity, the land evaluation aspects of GILES, which can be carried out better at a medium (detailed or semidetailed) scale than at small scale.
Part of GILES is this Manual with the general description of GILES and its main facilities, a user's manual with a tutorial that leads through the sample evaluation, background information on land evaluation, instructions for installing and for interfacing to commercial databases.
Computer, GIS and land evaluation system brought with them a considerable amount of jargon. For those not familiar with these new technologies, two Glossaries of terms used in this Manual, are given at page 279-289.
GILES facilities consist of two components:
a) 'Geographical Information System component', for thematic map retrieval, entry, modification and (general) manipulation of spatial data. The theoretical background and some technical aspects are discussed in this part (see Section 2.2; p.20).
b) 'Land Evaluation system component', for specific processing of physical environmental maps for the assessment of agricultural suitability and of conservation need for planning the most appropriate land use (see Section 2.3; p.;29).
Before use can be made of the advantage of a computerized geographical information and land evaluation system, some change of the methodology applied and some investment in hardware and training have to be done (see Sections 2.4-2.6; p.33).
Four components make up any kind of computerized processing such as GILES (see App.5; p.203):