engleski

GIS technology as a Tool for Production of Basic Geological Map of the Republic of Croatia, scale 1:50, 000

Implementation of GIS technology in mapping and producing of geologic maps and creating of an accompanying geologic information database has a strong influence on the method of field geologist’ s work because it demands a new way of thinking. The analyses of geological data obtained from classical maps (paper format) are restricted because of the lack of related databases. On the contrary, a digital geologic map can be drawn at a different scale, with different projections and singular geologic features ; for example lithology or age or structural elements as well (JOHNSON et al., 1999). Also, the geologic data from the map can be combined to external databases such as topographic, geochemical, agricultural, and similar ones for queries and analyses with specific requirements. The main goal of the represented project is the production of a lithostratigraphic geologic map, scale 1:50, 000, which will be the basis for developing a geologic model of a digital database. The development of the digital database is based on devising a standard geologic data entry and structure of the database. The model should be easy to use and extendable with any kind of computer data. Several types of data entry will be distinguished: (1) the data collected in the field, (2) additional tables with laboratory results and (3) digitally vectorized geologic map features. A Microsoft Access database form of tables is customized to accept field data. The standardization of geologic data and input form is made by Task Force RaSULiN. The data include a unique identification code - ID, date, x, y, z coordinates, rock description, name of the lithostratigraphic unit, structural measurements, general description and other data. The data are mostly selected from a defined list in the descriptive tables so that the result can be efficiently retrieved. The specialized sub-databases: sketches, photos, lithologies, fossils, sample, paloeotransports and structural measurements are linked to the field database. The graphical data entry is obtained by scanning, georeferencing and vectorizing of spatial geologic and other objects from a geologic map. The geologic features are presented as lines, points, polygons and their attribute tables. A feature may have more than one attribute table. For example: a fault can separate polygons of lithostratigraphic units and continue into other polygons. It consists of three attribute tables: (1) specific fault data, (2) data about the contacts between lithostratigraphic units and (3) data for polygon boundaries of the lithostratigraphic units (JOHNSON et al., 1999). The attribute tables are linked to the related tables, description tables, cartographic tables, field database and sub-database tables. The integration of geologic spatial information and associated tabular data into a logical relation geologic database is made in GIS software ESRI ArcInfo 8.3 (RICHARD, 2004). The data model of this application is a geodatabase. The geologic data and their relationships are controlled by setting domains, subtypes and topology rules in the geodatabase between feature datasets or feature classes of faults, geologic contacts, lithostratigraphic units and field points. The geodatabase could explore the data for a specific purpose by means of thematic layers for a particular geologic data set, water, roads, etc. Geographic information systems allow the manipulation and analysis of tabular and/or spatial geologic data sets. Both of them can be stored, edited, modified, updated and these changes are affected throughout the whole geologic relational database. The implementation and evaluation of the Geographical information systems in geology, especially in mapping technology require some conditions to be met: standardization of topography, standardization of geologic data entry (graphical or tabular), a comprehensive structure of geologic database model and friendly access to spatial and tabular information. A well designed and maintained geologic database could be used for producing various geologic maps, queries and analyses (RICHARD & ORR, 2001).

GIS ; database ; mapping ; basic geologic map ; Croatia

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