USING THE G.I.S. INSTRUMENTS TO OPTIMIZE THE DECISIONAL PROCESS AT THE LOCAL COMUNITIES LEVEL
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USING THE G.I.S. INSTRUMENTS TO OPTIMIZE THE DECISIONAL PROCESS AT THE LOCAL COMUNITIES LEVEL

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A G.I.S. is an information management tool that helps us to store, organize and utilize spatial information in a form that will enable everyday tasks to be completed more efficiently.

A G.I.S. is an information management tool that helps us to store, organize and utilize spatial information in a form that will enable everyday tasks to be completed more efficiently.

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USING THE G.I.S. INSTRUMENTS TO OPTIMIZE THE DECISIONAL PROCESS AT THE LOCAL COMUNITIES LEVEL Document Transcript

  • 1. USING THE G.I.S. INSTRUMENTS TO OPTIMIZE THE DECISIONALPROCESS AT THE LOCAL COMUNITIES LEVELMihai Valentin Herbei – Ph. D. Eng., University of Agricol Sciences and Veterinary Medicine of BanatTimisoara – Faculty of AgronomyUlar Roxana - Univ. assist. Ph. D. student, Eng. University of Petrosani, Faculty of MineABSTRACT: "Every object present on the Earth can be geo-referenced", is the fundamental key ofassociating any database to G.I.S. Here, term database is a collection of information about things andtheir relationship to each other, and geo-referencing refers to the location of a layer or coverage inspace defined by the co-ordinate referencing system. G.I.S. is a system of hardware and software used forstorage, retrieval, mapping, and analysis of geographic data. Practitioners also regard the total G.I.S.as including the operating personnel and the data that go into the system. Spatial features are stored in acoordinate system (latitude/longitude, state plane, UTM, etc.), which references a particular place on theearth. Descriptive attributes in tabular form are associated with spatial features. Spatial data andassociated attributes in the same coordinate system can then be layered together for mapping andanalysis .G.I.S. can be used for scientific investigations, resource management, and developmentplanning.1. Introduction and data presentation for administrative support or for decision support. (Fig. 1. and 2). G.I.S. differs from CAD and other graphicalcomputer applications in that all spatial data isgeographically referenced to a map projection in anearth coordinate system. For the most part, spatial datacan be "re-projected" from one coordinate system intoanother, thus data from various sources can be broughttogether into a common database and integrated usingG.I.S. software. Boundaries of spatial features should"register" or align properly when re-projected into thesame coordinate system. Another property of a G.I.S.database is that it has "topology," which defines thespatial relationships between features. The fundamentalcomponents of spatial data in a G.I.S. are points, lines(arcs), and polygons. When topological relationshipsexist, you can perform analyses, such as modeling theflow through connecting lines in a network, combiningadjacent polygons that have similar characteristics, andoverlaying geographic feature. The main purpose forintroducing the G.I.S. technology consists in increasingthe efficient possibilities for maintaining and updatingthe data. In the narrow sense, a G.I.S. consists of asystem for data input in vector form, in raster form andin alphanumeric form, a CPU containing the programsfor data processing, data storage and data analysis andof facilities for visualization and hard copy output of thedata. In a broad sense, a G.I.S. includes the data, whichare managed by an administration or a unit conducting aproject for the purposes of data inventory, data analysis Fig. 1 The sketch of G.I.S.
  • 2. Fig.2 Concept of a G.I.S.2. Structure of a G.I.S. application necessary quality, in conditions of maxim efficiency. Into the fig. 3 it is presented a general scheme of The G.I.S. technology is used in all fields for which principle of sources that can be taken into considerationthe spatial information is relevant, that means in all for making the digital map.fields that use the geographical map for stocking, Acquisitioning the data is the process of conversionanalyzing and representing the data which are of the data for the shape in which it is exists in one thatprocessed. can be used by a G.I.S. No matter what is the field, any G.I.S. application The first aspect we may take into account here is theincludes a spatial data base (a digital map) and a soft map precision standard of 0,2 mm that depends on thewhich exploit these data bases. scale assures the G.I.S. data to have a precession like The digital map must contain the spatial data into the following table:specific to any field whose it is designated to thisapplication. In order to furnish some useful information, Table 1this data base must be actual, which means it must CARTOGRAPHIC CLASSIC ACCURACYrepresent correctly the terrain (geographic space) that is ACCURACY MAP OF G.I.S.always under changing. SCALE DATA This exploitation soft is made from many functions 1: 25000 5mof analyzing the spatial data contained into the digital 1: 10000 2mmap and of visualizing the resulted information, specific 1: 5000 1m 0,2 mmto the application field. 1: 2000 0,4 m 1: 1000 0,2 m3. Accomplishing the digital map 1: 500 0,1 m The digital map must be made by vaporizing all the In order that the spatial data can be obtained from aexistent resources based on a good analyze of these great variety of sources, it must be done the differencecontent and the involved costs, following to assure the between acquisitioning new data and of the existent one.
  • 3. Each data source presumes the existence of somespecial programs that are used for transforming the datainto a shape of the digital map. Fig. 4 Point, line and area objects Fig. 3 Data sources for G.I.S.4. Models of data from the digital map There are two important components of geographicdata: its geographic position and its attributes orproperties. In other words, spatial data (where is it?) andattribute data (what is it?). Geographic position specifiesthe location of a feature or phenomena by using acertain coordinate system. The attributes refer to theproperties of spatial entities such as identity (e.g., Fig. 5 Vector formatmaize, granite, lake), ordinal (ranking, e.g., class 1,class 2, class 3, and so on), or scalar (value, e.g., water A vector format represents the location and shape ofdepth, elevation, erosion rate, and so on). They are often features and boundaries precisely. Only the accuracyreferred to as non-spatial data since they do not in and scale of the map compilation process; the resolutionthemselves represent location information. of input devices; and the skill of the operator inputting Spatial features in a G.I.S. database are stored in data limit the precision.either vector or raster form. G.I.S. data structures In contrast, the "raster" or "grid-based" formatadhering to a "vector" format store the position of map generalizes map features as cells or pixels in a gridfeatures as pairs of x, y (and sometimes z) coordinates. matrix (Fig. 6). The space is defined by a matrix ofA point is described by a single X-Y coordinate pair and points or cells, organized into rows and columns. If theby its name or label. A line is described by a set of co- rows and columns are numbered, the position of eachordinate pairs and by its name or label. In reality, a line element can be specified by using column number andis described by an infinite number of points. In practice, row number, which can be linked to coordinatethis is not a feasible way of storing a line. Therefore, a positions through the introduction of a coordinateline is built up of straight line segments. An area, also system. Each cell has a attribute value (a number) thatcalled a polygon, is described by a set of coordinate represent a geographic phenomenon or nominal datapairs and by its name or label, with the difference that such as land-use class, rainfall or elevation. Thethe coordinate pairs at the beginning and the end are the fineness of the grid or, in other words, the size of thesame (Fig. 4,5). cells in the grid matrix, will determine the level of detail at which map features are represented. There are advantages to the raster format for storing and processing some types of data in G.I.S..
  • 4. Fig. 6 Raster format The "raster" or "grid-based" format generalizes map Fig. 8 Attribute linksfeatures as cells or pixels in a grid matrix (Fig. 7). In both models the geographic data of a certain territory are organized on many layers or thematic coverage (Fig. 9.). The digital map is a special territory is represented by the sum of all layers that have been defines. A derived map will be constituted from a layer or a certain combination of layers from the existent ones. One of the main problems that should be solved inside the project of informatics system will be to define the layers that form the digital map and to establish the entities that belong to each layer. Fig Fig. 7 Vector-raster relationship The vector or the raster data are also linked (Fig. 8)to non-graphic information specifying place names andobject numbers, which in databases may further belinked to a great variety of coded or alphanumericalattributes (e.g. owners of a parcel, inhabitants of ahouse, characteristics of a utility feature, statistical datafor a defined area). Fig. 9 Layers in a Digital Map 5. Spatial analyses
  • 5. requires both geographic and other information (as well The most important feature of a G.I.S. consists in its as specific models).capacity to make spatial analyses, which means to The main spatial operations are as follows:process the spatial data (geographical data) with the • Operations on a single layer;purpose to obtain information (reports) regarding the • Operations on multiple layers;studied area. With this feature of spatial analyze is • Statistic analyze;different the software dedicated to G.I.S. over the • Network analyze;software like the CAD. The processing of spatial data is • Analyze of the surfaces – making the digital modelmade based on some algorithms specific by using own of the terrain.operations for these such data. A geographic information system must include some 6. Examples of spatial analysesfacilities for answering to the following 5 generalquestions: 6.1. Operations on a single layer  LOCATION: "What is at….?"The first of these questions seeks to find what exists at a These operations are called also operations on theparticular location. A location can be described in many horizontal. For the vectorial maps it is necessary that theways, using, for example, place name, postcode, or layers should contain only the graphic primitives ofgeographic reference such as longitude/ latitude or x and same type, so it will be used the group of operations ony. many layers.  CONDITION "Where is it..?" These operations on the horizontal are as follows:The second question is the converse of the first and the manipulation of the graphic primitives (operationsrequires spatial data to answer. Instead of identifying over the contours and analyze of proximity), theirwhat exists at a given location, one may wish to find selection (their identification) and their classificationlocations where certain conditions are satisfied (e.g., a (grouping the graphic primitives in classes in order tonon-forest area of at least 2,000 square meters in size, make a statistic analyze).within 100 meters of a road, and with soils suitable for The operations that are made over the contours aresupporting buildings). as follows: selecting a part of the layer (CLIP – coping a  TRENDS: "What has changed since./.?" part of a coverage), removing some graphic primitivesThe third question might involve both of the first two (ERASE), creating some subdivisions (SPLIT),and seeks to find the differences within an area over assembling some adjacent maps (MAPJOIN), removingtime, for example, changes in forest cover or the extent the limits that separate the polygons of same typeof urbanization over the last ten years. (DISOLVE) and eliminating some lines (ELIMINATE).  PATTERNS: "What spatial pattern exists...?” The analyze of proximity represents theThis question is more sophisticated. One might ask this identification some contours at equal distance to graphicquestion to determine whether landslides are mostly primitive (BUFFER)(Fig. 10).occurring near streams, or to find out which are thetraffic points where the accidents occur more frequently.It might be just as important to know how manyanomalies there are that do not fit the pattern and wherethey are located.  MODELLING: "What IF...?""What if…" questions are posed to determine whathappens, for example, if a new road is added to anetwork or if a toxic substance seeps into the local Fig.10 Diagram of simple buffers and a setbackgroundwater supply. Answering this type of question
  • 6. Fig. 11 Geometric spatial queries6.2. Operations on multiple layers In order to accomplish the operations on multiplelayers is needed that all maps involved in this processshould be at the same scale and should have the samesystem of coordinates. These operations are called operations on verticaland they are based on the relations between data ondifferent layers. So, a complex layer may be dissolvedin thematic layers and many layers may be combined.These operations are of type “overlay”, proximityanalyze and analyze of spatial correlations. The overlay analyzes (Fig. 10) creates somecombinations between graphic primitives on differentlayers and built links between data based on somelogical conditions imposed of type: AND, OR, XOR, Fig.12 Example of Polygon-overlay analyzeNOT (negation). These operations are as follows: UNION andINTERSECT (intersection). UNION makes that two ormany layers should overlap and should result a newcoverage. It uses the logic operator OR and it does notthat the layers should contain the same type of graphicprimitives. INTERSECT uses the logic operator AND,the result being a coverage that contains the commonpart from the layer and data from the second layer. Inthis situation the layers must be at the same type ofgraphic primitive. This operation is more used on layers that containonly polygons. Fig.13 Example of Raster-overlay analyze
  • 7. execute responsibilities, and respond to request from6.3. Generating and interpreting the digital model of citizens, potential developers and other clients. the terrain To accomplish the digital maps and to introduce the G.I.S. systems into local community sectors will increase the level and quality of their decisional process. Being very used in different fields, and starting from the information necessary to any citizen and till environment protection, from the marketing strategies to resources administration, the G.I.S. marked a revolution in solving the problems. The quality information means quality decisions. And G.I.S. offers this possibility, transforming some simple information in real information and offering the interactive access to them. 8. References 1. DUMITRU, G. „Geographic Information System”, Ed. Albastra, 2001 Fig. 14 The 3D model of the surface 2. HERBEI M. - “Performing a Geographic Information System into the areas affected by the mining exploitations by using modern techniques and technologies” - Doctorate thesis, Petrosani, 2009 3. HERBEI O., HERBEI M. – “Geographic Information Systems. Theoretical and applications”, Ed. Universitas, Petroşani, 4. KONECNY, G. – “Geoinformation”, London, 2003 Fig.15 Example of map of Slope7. Conclusions A geographic information system is an informationmanagement tool that helps us to store, organize andutilize spatial information in a form that will enableeveryday tasks to be completed more efficiently. Sinceits rapid growth over the last two decades, G.I.S.technology has become a vital element for us tomaintain and integrate information. G.I.S. software, andthe hardware required to operate it, have become muchmore affordable and easy to use. This has resulted in theability to develop a G.I.S. without making largeinvestments in software, hardware and the support staffthat were once needed to implement it. With theimplementations of G.I.S., we will see dramaticimprovements in the way we access information,