3 introduction gis

An Introduction to GISLand Information Systems

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Silvia Franceschi

Friday, September 10, 2010

An Introduction to GIS - Land Information Systems

Silvia Franceschi

Objectives:

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Land Information Systems (LIS)

Geographic Information Systems (GIS) ‏

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Definition: There is not a precise definition for the meaning of GIS

The definition depends on the “cultural context”

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Silvia Franceschi

Definition: There is not a precise definition for the meaning of GIS

The definition depends on the “cultural context”

The proliferation of specialised slang

Difficulties in understanding between professionals

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Information System:

Set of tools, procedures, and people that have the task to organise, select, archive, and communicate the data regarding the activities of an organisation (public or private).

Its objective is to make available to the decision makers all the information necessary to make the best possible choices.

“Set of procedures, founded on the use of information technology, used to archive and process georeferenced data” (Aronoff 1989)

“Set of tools to acquire, extract, process, archive, and REPRESENT spatial data from the real world” (Burrough 1986)

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Originally developed in Canada, GIS soon spread all over the world. They

are mainly used by public bodies to manage land data.

The use of GIS has grown greatly in the last ten years as an essential tool

for urban planning, and the management and planning of environmental

resources.

Their diffusion is due, mainly, to the great capacity to save, recover,

analyse, model, and map large areas by means of very large amounts of

spatial data.

GIS are now widely used in the environmental field and in research

because of the possibility to access different data correlated by their

position in space.

History

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Information System:GIS are information systems dedicated to the study and management of

geographic data. By means of these tools it is possible to:

- collect;

- model;

- manipulate;

- analyse; and

- present

geographically referenced data or, to put it better, GEOREFERENCED data.

GIS allows the superposition of various levels of information regarding an

area. It is therefore possible to obtain a better understanding of the

processes that affect the area and the factors that characterise it. 7



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Information System:

Immagine non modificabile.



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GIS – What is it?Geographic Information

Information relating to the position of an object on the surface of the Earth

Knowledge of “what is in a certain place at a certain time (we must not forget

the time factor)”

Geographic Information Technologies

Technologies for working with these data

Global Positioning Systems (GPS) ‏ Remote Sensing (RM) ‏ Geographic Information Systems (GIS) ‏

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GIS – Geographic Information System

1. Complete tool suitable for land

representation and the processing of

data associated with georeferenced

objects.

2. To each object (points, lines, areas)

spatial coordinates are assigned that

are congruent with the cartographic

base reference.

3. GIS integrates the characteristics of various types of software.

To use a GIS is not limited to just using a software tool, but rather it

means adopting a working method.

CAD DATABASE

ImageProcessing

GIS

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What a Geographic Information System (GIS) is not.The most common error when referring to GIS is to confuse the

Geographic Information System with one or more of its component

technologies. - cartographic base

- GIS is not a digital cartography

- the cartographic base is simply one of the starting

points upon which a GIS is developed

- GIS is not a more or less developed software package

- it is a system that requires the existence of a well-

defined project by the end user

- it is a MODEL REPRESENTATION OF THE REAL

WORLD and, therefore, a working method 11



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Application Fields- Agriculture (land use)‏- Economics (market analyses) ‏- Defence (logistics, planning) ‏- Ecology and landscape conservation

- Utility networks (water, gas, power)‏- Civil Protection

- Natural Resource Management

- Land Registry

- Forestry

- Public Health (epidemiology) ‏- Education

- Geography

- Oceanography

- Real Estate Management

- Earth Observation

- Telecommunications

- A d m i n i s t r a t i v e D a t a

Management

- Infrastructure Management

- Preparation of Maps and

Databases

- Mining and Extraction

- Surveying and Topography

- Transportation and Logistics

- Urban Planning

- Research

...

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How does a GIS work?

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Using Data

GIS allows for the organised archiving of data used in analytical and

management activities.

The geographic data can be correlated with each other, organised into

structures and according to needs.

Generally, the data that can be imported are:

- graphic elements (points, lines, areas) ‏- images

- attribute data associated with the preceding elements

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Position: What is there in ...?

Conditions: Where is ...?

Trends: What has changed ...?

Spatial distribution: What spatial distribution is there?

Modelling: What happens if ...?

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What questions can be answered?



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Position: What type of soil can be found at these coordinates? Or near

this type of structure?

Conditions: Identify the areas which fall within the temporal buffer

zone (60 days) for water wells

Trends: What type of vegetation has undergone changes in comparison

with the 1950 map?

Spatial distribution: Is there a correlation between vulnerable areas

and nitrate pollution?

Modelling: What happens if the public wells of Milan are polluted?

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Examples



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Main Functions• Entering and verifying data

• Data transformations: set of operations used to correct and homogenise

the data set (coordinate transformation, editing,...)

• Data storage: in an appropriate DBMS

• Analysis: application of conceptual models that reproduce the physical

phenomenon being studied, with new data being created as a

consequence

• Output of results: in various forms (digital, cartographic...) ‏• Models of geographic data: the data of a geographic data base are made

up of three components:

• Spatial aspect: geometry/topology

• Quality aspect

• Semantic aspect: alphanumerical, numerical, and statistical attributes



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A MAP can be simply defined as a graphic representation of the real

world. Maps are only a representation, it is not possible to include in a

map all the complexity of reality.

Maps can be used to visualise cultural and physical aspects of an

environment.

Topographic maps are those that represent general information, such

as the disposition of roads, land use, altitude, rivers, water bodies...

However, there are also maps that represent non-geographical

elements, such as the maps of meteorological evolution, temperature,

pressure... The use of these maps is decidedly more specialistic than

that of topographical maps.

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Cartography



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Set of: coordinates associated to elements (points, lines, polygons) ‏ relationships between elements attributes of the elements

It can be seen as the reverse of traditional paper mapping: traditional mapping: drawing coordinates digital mapping: coordinates drawing

The content and uses of digital mapping are greater than those of

traditional mapping (in fact, the latter can be derived from the

former).

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Cartography



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The concept of SCALE may seem redundant in digital mapping because

it is possible to view and print the data at an magnification, given that

the coordinates are absolute.

However, the scale depends on the precision of the coordinates.

Nominal scale: scale at which the map print has the same metric

requirements of the traditional map (precision, graphical error).

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Scale



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There are three types of relations between elements: : spatial topological proximity

Directional relations: they depend on the orientation of the map opposite north on the other side south above east below west

and combinations of orientations.

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Spatial Relations between Elements



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EQUIVALENCE

PARTIAL EQUIVALENCE

CONTAINMENT

ADJACENCY

SEPARATENESS 22

Topological Relations



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These indicate, QUALITATIVELY and QUANTITATIVELY the distance

between objects: qualitative:

near far in the vicinity of .. quantitative: d=1532 m

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Proximity Relations



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In digital cartography the information layers can be separated (very

often they need to be).

HYDROGRAPHIC NETWORK

SETTLEMENTS

PRIMARY ROAD NETWORK

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Information Layers



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Spatial data is traditionally divided into two classes: RASTER and

VECTOR

FIELDS or RASTERS: objects defined almost everywhere within the domain of

interest, very often continuous. For example, temperature, pressure, altitude.

They are represented in discrete form with regular matrices of attributes

(matrix models or georeferenced rasters), triangular irregular networks (the TIN

model), or with contour lines.

ELEMENTS or VECTORS: discrete and discontinuous objects that are precisely

defined. For example, buildings, administrative areas, road networks.

They are represented with vectorial models, that may also be topological, with

associated tables of attributes.

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Data: Elements and Fields



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FieldsAltitude (DTM: Digital Terrain Model) ‏

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DTM

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Raster



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"Digital Elevation Model" (DEM): it represents the elevations of a

particular surface. When using a DEM, the reference surface must

always be stated.

"Digital Terrain Model" (DTM): it represents the elevations of the

surface of the Earth, that is to say the terrain. A DTM is a specific case

of a DEM where the surface represented is that of the Earth.

“Digital Surface Model” (DSM): it represents the elevation of the surface

of the Earth, including those elements that are above the surface.

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DTM/DEM



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The DTM and DEM describe a continuous surface by means of a

finite number of three-dimensional points (x,y,z values) in space

(x,y,z). The xyz triplets are usually distributed irregularly because

they have been obtained by different measuring methods. These

irregular points are generally put into a regular grid (usually square

with the same amplitude in the x-direction as in the y-direction) by

means of various interpolating methods (e.g. kriging, spline, least

squares,...). Each triplet (x,y,z) of the DTM/DEM represents,

therefore, an area, that is to say, a square of the grid. The squares

are called CELLS or PIXELS (= picture elements).

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DTM/DEM



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DTM



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TIN - (Triangular Irregular Network) ‏

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Contour Lines



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Contour Lines



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Elements: Points, Line, and Areas



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The elements are made up

of:

geometric primitives: point curve surface

topological primitives: node edge face

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Elements



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Rasterisation of the Elements

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Rasterisation of the Elements



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Vector

advantages memory use explicit topology “resolution”, precision

of the coordinates

disadvantages some operations are

taxing overlay is complicated

Raster

advantages algebra on maps operations are simple

and intuitive for the

user

disadvantages memory operations implicit topology

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Comparison: Raster - Vector



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Raster - Vector



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Raster - Vector



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Raster - Vector



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Topological relations are relations between objects that are independent

of the orientation of the map, and invariant to elastic or continuous

deformations (e.g. change of reference system and/or coordinate

system). These relations are used to express congruity constraints

between objects.

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Topology




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These are based on frames with which space is divided into regular shapes

and sizes.

Each element is defined by its row and column numbers (2D) and layer

number (3D).

The position of the origin of the reference system must be defined.

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Raster Geometric Primitives



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GRID: regular distribution of

points defined by the nodes of the

grid, derivable from a 2D structure.

They are completely defined by

row and column numbers.

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PIXEL: two-dimensional geometric

primitive, corresponding to the

basic element of a 2D structure.

Raster Geometric Primitives - 2D



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NODE: 0-dimensional primitive. It can be connected (by an edge) or

isolated.

EDGE: 1-dimensional topological primitive. It represents an orientated

connection between two nodes (that may coincide).

FACE: 2-dimensional geometric primitive, described by an external ring

(a closed set of edges that do not cross) and either none or many

internal rings.

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Topological Geometric Primitives



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The most common vector file format is undoubtedly the shapefile

format: .shp.

A shapefile is made up of a family of files which, specifically, includes: .shp contains the information related to the form of the features .shx contains an index of the position of the features to speed up the

queries made .dbf contains the attributes related to the features .prj contains the information related to the coordinate system and the

projection of the data .shp.xml contains the metadata linked to the features

Other formats supported by the vast majority of GIS are: tab, dxf, dwg,

E00, ..., ascii.46

Vector File Formats



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The most common are:

• TIFF

• GIF

• JPEG

• ASCII

The raster files of images that can be viewed with a GIS need to contain

information relating to the coordinate system and the projection. Files

such as TIFF files, therefore, need to be georeferenced. That is to say,

they must be GEO-TIFF files. The information relating to the projection

can be included within the TIFF file itself or it can be written to a

separate file, usually with extension TFW (or JGW).

ASCII files contain all information relating to the region and the

localisation of the data. 47

Raster File Formats



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•The most widespread GIS in the field of open source GIS are:

-GGRASS: the oldest of the open source GIS. Originally developed by the United States Department of Defence, it is very powerful in raster analysis (www.grass.itc.it)

-JUMP: viewer which offers the possibility of vectorial data analysis (http://openjump.org)

-GVSIG: viewer which offers the possibility of vectorial data analysis. There is also an integration of raster components but not sufficient for raster analysis (www.gvsig.gva.es)

-QGIS: considered the simple graphic interface for GRASS (www.qgis.org)

-JGRASS: GIS dedicated to environmental analysis, it allows the viewing and analysis of raster and vector data (www.jgrass.org)

-uDig: vectorial data and image viewer (http://udig.refractions.net)

Overview of Open Source Desktop GIS


http://www.grass.itc.it

http://www.grass.itc.it

http://openjump.org

http://openjump.org

http://openjump.org

http://openjump.org

http://www.qgis.org

http://www.qgis.org

http://udig.refractions.net

http://udig.refractions.net


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I most widespread GIS in the field of commercial GIS are:

• ESRI: ArcGIS, Arcview, Arcreader... probably the the biggest family of GIS software in the commercial field (www.esri.com)

• ERDAS-IMAGINE: satellite image management (www.geosystems.de)

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• ERMAPPER: high-resolution image management ( orthorectification, mosaic, reprojection, colour balance and compression)

• MAPINFO: very easy to use; best described as a viewer that manages vectorial data well (www.mapinfo.com)

• AutoCAD Map 2004: advanced management of geographic data along with image management (www.autodesk.com)

Overview of Commercial Desktop GIS


http://www.esri.com

http://www.esri.com

http://www.geosystems.de

http://www.geosystems.de

http://www.mapinfo.com

http://www.mapinfo.com

http://www.autodesk.com

http://www.autodesk.com


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The database is an essential component of the GIS in that it contains all the information that will be viewed and analysed, both with desktop GIS and WebGIS. In the field of proprietary databases, the most widespread are:

• ORACLE: with a spatial extension to support geometries (Oracle-Spatial)• ArcSDE: spatial database by ESRI

• Access: this is not a spatial database but a mechanism can be constructed to link information to geometric features.

The most widespread open source databases are:

• Postgres: the most popular, with spatial extension PostGIS

• HSQLDB: this is not a spatial database, it is only a relational database ...

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GIS Support Databases



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Open Source WebGIS

The two open source development environments for geospatial data

currently used are: GEOSERVER MAPSERVER

Graphic interfaces for these products are available for the production of

WebGIS such as those that are often found on the websites of public

bodies and research centres. Some tools of this type are: Ka-Map Py-WPS ...

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GIS

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Italian Digital Cartography

Immagine non modificabile



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With respect to the purely geometric representation of objects, a GIS

also needs to store and manage the information about the mutual

spatial relationships between the various elements. That is, it must

structure the data and define the topology.

As well as geometric and topological data, the GIS must also allow for

the insertion of descriptive data relative to individual real objects, that

is to say the ATTRIBUTES.

The structure that is capable of saving the spatial and geometric

relations and attributes is referred to as a relational structure.

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GIS Characteristics



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In a GIS, the coordinates of an object are neither stored with respect to

an arbitrary reference system nor with respect to the coordinate system

of the device being used. They are stored according to the reference

system in which the object is really found and with their real

dimensions, not to scale.

The scale of representation becomes solely a parameter used to define

the level of accuracy and the resolution of the graphical information.

Depending on the scale, smaller elements may not be visualised and one

sees only areas of terrain characterised by the same quantity.

GIS allows us to manage the data like 3-dimensional objects in a real 3-

dimensional system. No longer do we need to simply attribute a height

to an object. 55

GIS Characteristics



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Starting from a TIN, a DTM or a DEM it is possible to:interpolate contour lines

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GIS Characteristics



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GIS Characteristics

Starting from a TIN, a DTM or a DEM it is possible to:interpolate contour linescarry out a visibility analysis



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GIS

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Starting from a TIN, a DTM or a DEM it is possible to:interpolate contour linescarry out a visibility analysisgenerate longitudinal profiles

GIS Characteristics



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A partire da un TIN, un DTM o un DEM è possibile:interpolare curve di livelloeffettuare un'analisi di visibilitàgenerare profili longitudinali

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GIS

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Starting from a TIN, a DTM or a DEM it is possible to:interpolate contour linescarry out a visibility analysisgenerate longitudinal profilescarry out slope analysis, exposition analysis...

GIS Characteristics



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GIS

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Starting from a TIN, a DTM or a DEM it is possible to:interpolate contour linescarry out a visibility analysisgenerate longitudinal profilescarry out slope analysis, exposition analysis...calculate real distance, taking account of the vertical coordinate

GIS Characteristics



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GIS

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Starting from a TIN, a DTM or a DEM it is possible to:interpolate contour linescarry out a visibility analysisgenerate longitudinal profilescarry out slope analysis, exposition analysis...calculate real distance, taking account of the vertical coordinatequery a list of attributes and extract the required values

GIS Characteristics



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GIS

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Starting from a TIN, a DTM or a DEM it is possible to:interpolate contour linescarry out a visibility analysisgenerate longitudinal profilescarry out slope analysis, exposition analysis...calculate real distance, taking account of the vertical coordinatequery a list of attributes and extract the required valuesextract the morphological characteristics of the terrain

GIS Characteristics



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GIS

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Starting from a TIN, a DTM or a DEM it is possible to:interpolate contour linescarry out a visibility analysisgenerate longitudinal profilescarry out slope analysis, exposition analysis...calculate real distance, taking account of the vertical coordinatequery a list of attributes and extract the required valuesextract the morphological characteristics of the terrainprocess quantities relative to the hydrographic network

GIS Characteristics



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GIS

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Starting from a TIN, a DTM or a DEM it is possible to:interpolate contour linescarry out a visibility analysisgenerate longitudinal profilescarry out slope analysis, exposition analysis...calculate real distance, taking account of the vertical coordinatequery a list of attributes and extract the required valuesextract the morphological characteristics of the terrainprocess quantities relative to the hydrographic networkcarry out stability analysis of the catchmentcarry out hydrological analysis at event scale...

GIS Characteristics



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JGRASSThe Research Centre for the development of algorithms implemented in JGrass is the Department of Civil and Environmental Engineering of the University of Trento (Italy) and CUDAM (University Centre for the Defence of Mountain Environments), also at the University of Trento. The Development Centre is HydroloGIS of Bolzano (Italy), although there are other developers at CUDAM in Trento.

The JGrass starting point is GRASS GIS, which currently represents the most important Open Source project in the GIS field. GRASS is slowly evolving towards an attractive solution for the commercial and productive sectors. The biggest obstacle to the commercial blooming of GRASS is without doubt its versatility problem. Many professionals use Windows and Mac-OS as the preferred operating systems, and many businesses do not provide the possibility of using Linux (which is the operating system upon which GRASS development is based). 73



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JGrass, developed to simplify the use of GRASS on different operating systems, has set itself the following objectives:

•versatility - the possibility to run GRASS on Windows, Unix/Linux and Mac-OS indifferently (write once, run everywhere)

•the possibility for anyone, by means of the framework that has been created, to develop with ease additional modules, particular functions, and application oriented interfaces by means of XML scripting

•scripting - the possibility to use a Java-based scripting language in order to automatise certain processes (programmer and scientific - work oriented)

•simplicity of use - menu bars, tool bars and icons aimed at simplifying the interface (end-user friendly)

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JGRASS



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Over the last number of years various attempts have been made to combine the strengths of Java and GRASS. The first of these was the wrapping of the GRASS libraries in Java by Alexandre Sorokine. Shortly thereafter, at the Centre for Environmental and Nuclear Sciences of the University of the West Indies (Jamaica), John Preston began to develop a Java/Swing application for the visualisation of geochemical maps.

At the beginning of 2003 Dr Rigon, of the Department of Civil and Environmental Engineering and CUDAM of the University of Trento, decided to support the Jamaican project in a concrete way by supplying funds and a developer, and coordinating with the research group at ITC, which includes Markus Neteler. In this way the development of JGrass began.

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JGRASS



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At the moment JGrass is an application that can be run locally, although

the future implementation of remote running is planned. It is a Java/

RCP application based on an MDI (multiple document interface) and

provides standardised ways of interaction between the interface and the

GRASS kernel.

Although we are trying to keep JGrass, as much as possible, in "pure

Java", some parts are still written in the native language of GRASS by

means of Sun's API JNI technology.

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JGRASS



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JGrass is a free and open source GIS that can be freely downloaded

from the website:

www.jgrass.org

All the instructions for use are found on the same webpage, along with

documents of the available commands.

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JGRASS


http://www.jgrass.org/





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Thank you for your attention.

G. U

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3 introduction gis

Education

use of gis

meaning of gis

information necessary

land data

use of information technology

land representation

worlssilvia franceschifriday

management of geographic