geographical information systems (gis) - Битола · pdf fileenviromatics 2008 -...

1Enviromatics 2008 - Geographical information systems GIS

Geographical information systems(GIS)

Вонр. проф. д-р Александар Маркоски

Технички факултет – Битола

2008 год.


Introduction

“A computer based system, consisting of hardware, software, data and application. It provides scientific information considering spatial relation.

A GIS has to offer functions for

– input,

– storage,

– checkup,

– manipulation,

– integration,

– analyzing and

– alphanumeric as well as graphic presentation of spatial data.


Introduction (2)

• The integration of thematic data and information about the spatial situation (which will be presented cartographical),

distinguishes a GIS from a mere cartographic- or CAD-(Computer Aided Design) system.” (Weidenbach, 1999)

• GIS is not only a tool for making maps, it is a system for data analysis!


Other definitions for GIS

• The common ground between information processing and the many fields using spatial analysis techniques (Tomlinson, 1972).

• A powerful set of tools for collecting, storing, retrieving, transforming, and displaying spatial data from the real world (Burroughs, 1986).

• A computerized database management system for the capture, storage, retrieval, analysis and display of spatial data (NCGIA, 1987).

• An information system that is designed to work with data referenced by spatialor geographic coordinates. In other words, a GIS is both a database system with specific capabilities for spatially referenced data, as well as a set of operations or working with the data (Star and Estes, 1990).


Тerm GIS

The term GIS has different meanings.

Depending on the focal point it is:

– a collection of spatial data

– a collection of tools

– a package of hard- and software components

– a technology


Contributions to GIS-development

• Informatics (graphic, visualization, data base, security, system administration),

• geography and related fields (cartography, geodesy,

geomorphology, spatial statistics)

• user (public administration, engineering, location search, planning, geology, mining, forestry, marketing, criminology)


Visualization of Data


Elements of a GIS


The four-components-model of a GIS


Which Operations can be done with a GIS ?

• What is where?

• Where is what?

• What has changed since...?

• How is the spatial spread?

• What happens if...?

GIS uses the spatial allocation as a common key for different data records. Different issues are connected by their

geographic position.


Steps in a GIS project

1. Data acquisition (paper maps, digital files, remote sensing data, satellite data, field work),

2. Data preprocessing (preparation, integration, data conversion, digitising and/or scanning, edge matching, rectification),

3. Data management (variable selection, data definition, table design (performance, usability), CRUD policies/procedures (create: data entry; retrieve: view; update: change; delete: remove)),

4. Manipulation and analysis (address matching, network analysis, terrain modelling: slopes, different aspects),

5. Product generation (tabular reports, graphics: maps, charts).


What should be possible with a GIS?

• Management, analysis, connecting, presentation of geographic

data allows:

• automatic processing of geographic data, for example for making

maps,

• calculation of areas or distances

• calculation of slopes, exposition direction or visibility analyses,

• route planning, traffic management or logistics

• integration of data of different origins and types

• linkage of data to maps, to make complex spatial relations visible

• to answer spatial questions (for example: How many objects are

within a given distance to another object ?)

• the spatial modelling of complex scenarios (risk analysis, route

planning, resource management)


System architecture and components


Data Models

• What should a GIS represent?


Data Models (2)

Discrete Objects have

attributes as

• length

• volume

• land use

• type

Continuous Information for an area has gradients as :

• temperature

• content of water

• distribution of precipitation

• content of contaminants

Depending on the data concept there are raster/Grid-GIS or Vector-GIS. Systems working with both types, are named

hybrid systems.


Data Models


General Structure of a Grid


Vector Data

• The vector-structure is necessary for a object-related data

management in GIS. It is used for the realization of topologic structures and complex data models.

• Objects in Vector-GIS are points, lines, polygons.

• Every GIS-object in a view has a representation in the data

base. The attributes describe the objects and allow

selections and classifications.

• Classification by attribute (above) or selection by attribute

(below) are typical Data Base Management Methods. Selection or classification by spatial relations are typical

GIS-methods.


Vector GIS Objects


Atributes


Selecting objects


Selecting


Vector vs. Raster


Raster vs. Vector


Representation of Vector Data as Raster Data


Modelling topography special features

• Mass points and break lines from surveying,

• Triangulated irregular networks (TIN),

• 2,5-D Visualisation: Hillshading,

• Colour coded digital terrain model (DTM),

• 3-D Visualisation.


Grid data model

• Digital Elevation Model (DEM) in the background, showing the elevation, using graduated colors and shadows for visualizing 3rd dimension. In the foreground houses and water body (river) are shown, using vector data model.


Triangulated Irregular Network

• Base for developing the DEM (above) is a Triangulated

Irregular Network (TIN), based on measured points


1

3D-Presentation of a the

same TIN, example for vector based

representation of a surface

• irregular size of triangles,

• areas with higher and lower

density of knots


2

3D-Presentation of a grid, showing the same area (but different point of view)

• regular cell size


3

Combination of grid model

(surface) and vector model (houses)


Example for high resolution grid


Example: Visualization of water quality data, using polygons


Example: Visualization of water quality data, using polygons (cont.)


Fields of applications of GIS

• Automation of activities involving geographic data like map

production, calculation of areas, distances or route lengths,

measurement of slopes, aspect, view shed, logistics, route

planning, vehicle traffic, traffic management, land use

management, environmental planning, flood control, resource management, and others.

• Integration of data hitherto confined to independent domains (e.

g. Property maps, air photos).

• tying data to maps permits the succinct communication of complex spatial patterns (e. g. environmental sensitivity).

• providing answers to spatial queries.

• performing complex spatial modelling (e. g. scenarios for

transportation planning, disaster planning, utility design, risk

modelling).


Use of GIS in practical and researchfields

• Environmental and resource management (Watershed management, soil conservation, air pollution control,

agriculture, water harvesting, water supply),

• Urban planning, management and policy (Land

acquisition, environmental impact assessment),

• Surveying,

• Facility management (Infrastructure, telecommunication),

• Transport, Traffic, Logistics,

• Research and development (Environmental modelling, simulation and optimisation of energy, soil, water, climate,

etc. for risk assessment and decision support).


Scientific and engineering contributors to GIS

• Geography (provides techniques for conducting spatial analysis),

• Cartography (maps have been a major source of information input for GIS, long tradition in map design which is an important output from GIS),

• Remote sensing (images from air and space are major sources of spatial data, low cost and consistent update of input data),

• Photogrammetry (source of most data on topography used in GIS, uses aerial photographs for making accurate spatial measurements, IR photographs),

• Surveying (provides high quality data on positions of land boundaries, buildings, etc.),


Scientific and engineering contributors to GIS (2)

• Geodesy (high accuracy positional control for GIS, uses

GPS technology),

• Statistics (statistical techniques used in GIS analysis,

important to understand issues of error and uncertainty in GIS data),

• Operations research (optimising techniques used in GIS applications such as routing),

• Computer Science (GIS uses computer aided design

(CAD) technologies, computer graphics and visualisation, DBMS).


Software for GIS

• ArcInfo (Originated commercial GIS, clear market leader),

• Intergraph (Strong in design and facilities mapping, running hard

to match ArcInfo, its main modular GIS environment evolved from

its older CAD products, development of a new generation product of ist own code named Jupiter based on NT and object

technology)

• Bentley Systems (Originally developed the PC-based Micro-Station product GeoGraphics in cooperation with Bentley

Systems, but split in 1995, have very successfully continued to

develop and sell MicroStation GeoGraphics)

• Autodesk’s AutoCAD Map (Dominant CAD supplier and software company, fully topological AutoCAD Map since 1996,

illustrates convergence of CAD/GIS, many industrial applications

of AutoCAD for mapping)


Software for GIS (2)

• Graphic Data Systems (Originated as McDonnel-Douglas in-

house system, industrial applications, visualisation of technical products, now mapping the environment)

• ERDAS/Imagine, ER MAPPER, PCI, Envi (Origins in remote

sensing raster and vector data, new satellite data products, ER

MAPPER originating in Australia, PCI originating in Canada)

• GRASS (Public domain software, raster oriented with some vector

routines, but 1996 end of development and support announced),

• SICAD (Comparable with ArcInfo, powerful GIS with a lot of

functionalities for raster and vector data, object oriented

database)

• IDRISI (Comparable with ArcInfo, but not so powerful),

• MapInfo (Small GIS, useful for planning purposes, easy to

handle)


Problems in GIS practice

Up to now, there is no system that could solve all possible

tasks a GIS normally is confronted with:

• there is no unique data model that serves well for all GIS applications,

• there are no fully compatible geodata,

• there are no scale-independent geodata,

• there are no fully compatible/applicable commercial systems of data formatting,

• there are still severe problems with data exchange,

• there are some deficits in standardisation of GIS.


GIS Application Example:Hydrological Modelling using ArcView

• 1. Creating a DEM from point data file

• 2. Creating river network

• 3. Creating sub-catchments and pour points

Example is based on ArcView 3.x, with Spatial Analyst, 3D-Analyst and Hydro-Modeling Extension


Creating a DEM from point data file


Hydro-Modeling


Flow direction


Flow accumulation


sub-catchments


Questions?

geographical information systems (gis) - Битола · pdf fileenviromatics 2008 -...

Documents