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Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 1/22
Introduction to GIS
Paolo ZatelliDipartimento di Ingegneria Civile, Ambientale e Meccanica
Università di Trento
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 2/22
System: set of resources and procedures
Information: it is based on an information system
Geographic: all the information has a spatial reference
Geographic Information System
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 3/22
Resourceshumaninfrastructuresdata
Procedures
acquisitionarchivingprocessingpresentationtransmission
data
System
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 4/22
GISs are based on information systems and procedures:• generic• proprietary
Current systems use generic/standard hardware and software wherever possible (es. DBMS).
The choice of the right system depends on the purpouse.
Information System
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 5/22
All the features are spatially referenced
the basis for GISs is the numerical cartography
The system manages• geometry• topologyand their relationships with attributes (database).
Geographic Information System
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 6/22
Data are the most precious part of a GIS (except for HR!):• high production cost;• need of updates;• impossibility of recover (if data are lost and the objects they describe have changed).
They consists in• geometry;● attributes;● metadata.
Data
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 7/22
Numerical surveydesigned for the use of output data in a GIS
Pre-existing datafor non-GIS use
Traditional survey techniques• topographic• photogrammetric
Modern survey techniques• remote sensing• GPS• laser scanning• SAR
Existing documents• cartography• “data base”
Dipartimento di Ingegneria Civile e Ambientale Università di Trento
Data production
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 8/22
Acquisition
Primarymeasurements and data processing
Secondarydigitazingscanningattribures encoding
Data
geometryvectorrasterdigital image
attributes database
Data acquisition
Numerical surveydesigned for the use of output data in a GIS
Pre-existing datafor non-GIS use
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 9/22
Modeling External
Conceptual
Logical
Internal
external to GIS
modeling of the problem
data, tables, maps structure
file structure, ecc.
Data modeling
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 10/22
Map• geometric features (points, lines, areas)• attributes• legend (links attribures to features)
Non-spatial attributes are represented with symbols, colors, etc.
Planimetry is separate from altimetry (height=attribute of points or lines, contour levels).
Traditional cartography
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 11/22
Local and global knowledge of a region
Detection of the mutual relationships between features
Relationships between features are detected by the reader of the map, this process must be coded and made automatic for numerical cartography, to apply algorithms using these relationships.
Use of the map
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 12/22
A set of• coordinates associated to features (points, lines, areas)• relationships between features• features' attributes
It can be seen as mirror situation with respect to a traditional map tradizional map: drawing coordinates
numerical cartography: coordinates drawing
Numerical cartography contains more information and allows a broader range of use with respect to the traditional map (which can be created from numerical cartography, anyway).
Numerical cartography
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 13/22
The concept of scale seems to be useless in numerical cartography because it possibile to display/print a map with an arbitrary zoom factor, since coordinates are absolute.
Actually, in cartography,scale depends on the coordinates' accuracy.
Nominal scale: scale corresponding to a traditional map with the same metric requisites (accuracy accuracy of the plotter, usually 0.1-0.2 mm).
Scale
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 14/22
Qualitative content of a map depends on the scale
Large scale → drawingSmall scale → symbol
Most of the current GISs do not automatically select the way a feature is displayed as a function of the scale (generalization).
Generalization
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 15/22
Relationshipsdirectionaltopologicalneighborhood
Directional relationships: depend on map orientation.
facingon the other sideabovebelow
northsoutheastwest
and combinations
Spatial relationships between features
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 16/22
Equivalence
Separation
Proximity
Containment
Partial equivalence
Topological relationships
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 17/22
they evaluate in quantitative and qualitative ways the distance between features:
Qualitative•near•far•close to
Quantitative
d=1234m
Neighborhood relationships
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 18/22
In numerical cartography features layers are usually separate
hydrography
settlements
primary roads
Layers
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 19/22
In the environmental field, main uses are:• to create thematic maps, displaying the spatial distribution of phenomena (e.g. avalanche locations, population distribution, etc.)• to setup models of phenomena occuring on a region (e.g. a model of the risk of avalanche, a model of distribution of fauna).
Use of GISs
GISs are used whenever information has a spatial component (i.e. information is directly o indirectly connected to coordinates).
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 20/22
Thematic map – population by country
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 21/22
Avalanche risk model
Sup.criticaPascolo
Bosco rado
Bosco denso
Improduttivo
Introduction to GIS Introduction to GIS
Paolo Zatelli | Università di Trento | 22/22
This presentation is © 2014 Paolo Zatelli, available as
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