6 2 gis e book by GEORGE DIAMANDIS

6.2.1 GEOGRAPHIC INFORMATION SYSTEMS 1. INTRODUCTION 2. HISTORY 3. BASICS OF MAPPING 4. Definition of GIS 5. SOFTWARE gvSIG 6.2.2 REFERENCE SYSTEMS 1. INTRODUCTION 2. THE DATUM 3. GEODETIC REFERENCE SYSTEM 4. COORDINATE SYSTEMS 5. EPSG CODES 6.2.3 MAPPING THE DATA 1. INTRODUCTION 2. DATA TYPES: vector and raster 3. VECTOR DATA 4. RASTER DATA 5. THE SDI AND SERVICES WMS

6.2.1 GEOGRAPHIC INFORMATION SYSTEMS

1. INTRODUCTION The great complexity of the territory requires a series of tools that allow us to have a thorough knowledge of it for later use. The Geographic Information Systems, GIS onwards have been made in recent years as one of the most important working tools for researchers, analysts and planners, etc…, in all its activities whose input handling and analysis of a wealth of information (databases) related to various levels of spatial or territorial aggregation, which is creating the need for spatial information these users know about this technology. Although GIS Geographic Information Systems have strong analytical skills, they can not exist by themselves, must have an organization, personnel and equipment responsible for implementation and support, in addition it must meet an objective and be guaranteed the resources for maintenance.

2. HISTORY

The 60’s

Despite being a relatively new discipline, the early GIS back to the sixties, but in the fifties some interesting background succeeded (COMAS Y RUIZ, 1993). You could say that GIS, as such, emerged during the '60s when the first GIS was made in Canada called CGIS (Canadian Geographic Information System), in order to facilitate the work of conservation of natural resources available to the country. Alongside other similar projects developed in the United States, becoming the country where GIS will be more experimentation, both between public and private institutions, and therefore will be in this country where larger applications and importance to develop .

The 70’s

The first conference on GIS was organized by the IGU (International Geographical Union) and during this decade four agencies stand, one university, Harvard University two in the group of public institutions, United States Census Bureau (held in the seventies USCB) and United States Geological Survey (USGS), and finally, a private company, Environmental System Research Institute (ESRI).

During this decade, the National Center for Geographic Research and Analysis (NCGIA) whose purpose was to "develop basic research on geographic analysis using GIS” was created.

The 80’s In the early 80 `s, both in the U.S. and Europe, GIS had become a fully operational system, as the computer technology was perfected, it became less expensive and enjoyed greater acceptance. Currently are rapidly installing these systems in government agencies, laboratories or research institutes, academic institutions, private industry and the military and public facilities. The European Commission estimated a contribution to European industry more than 150 million Euros and two million jobs. The 90’s In the late eighties and throughout the nineties saw the further development of GIS in Spain to introduce beginning itself widely in public institutions and private companies. In the late nineties, in 1989, the Spanish Association of Geographic Information Systems (AESIG) was created in order to promote, support and enhance the use, development and analysis of GIS and Spatial Information and applications for a broad spectrum of users. From then until now a large number of public agencies have developed projects using GIS technology. XXIst Century There has been a dramatic evolution of geospatial systems (satellites, digital cameras, gps, etc ...) It began publishing in Internet mapping, the agency Open Geospatial Consortium (OGC) has developed a series of protocols and standards that provide the technological framework for achieving interoperability between different systems which favors the creation of Spatial Data Infrastructures (SDI). 3. BASICS OF MAPPING

Cartography

Science that deals with the study of the representation of the Earth's surface or part of it, through the use of maps, plans or charts and topographic, geodetic or photogrammetric data. Map

And measuring graphical representation of a portion of generally on a two dimensional surface area, but sometimes is spherical as in globes. The maps must emphasize the importance of scale, defined as the ratio between the size of the map and the actual dimensions of the surface is represented.

Remote sensing

Technique for obtaining information about a physical object or a phenomenon of the land surface without any direct contact with it.

Photogrammetry

Technique for planimetric and altimetric representation of the terrain through photographs of it obtained from an aircraft and under specific conditions.

Stereoscopy

Watching a pair of field images prepared perspective offered separately to each eye of the observer, for a space or raised image. In cartography, the art is able to collect, process and represent spatial information in three dimensions imitating the physical principle of vision.

4. Definition of GIS

Today the term GIS is widespread, especially among professionals working in planning or solving economic and environmental problems, which is why there are many definitions of it. Some emphasize its database component, other functionalities and others emphasize the fact that a support tool in the decision making, but all agree to refer to a GIS as an integrated system to work with spatial information.

As a model of the real world: “A computer model of the real world described in a system of reference earthbound established to meet requirements of specific information in response to a specific set of questions” (Rodriguez Pascual, 1993)

As a set of tools: “A system of hardware, software and procedures to facilitate the collection, management, manipulation, analysis, modeling, representation and display of spatially referenced data for solving complex planning and management” (National Center for Geographic Information and Analysis of the U.S.A., 1991)

As database: “A GIS is a database system in which most d these are geographically indexed, and on which a set of procedures to answer questions about spatial entities of the database is operating” (Smith et al 1987)

5. SOFTWARE gvSIG

There are several developed software for working with GIS technology , some have business license and other free license. In this case we will work with Free Software (Open Source ) called gvSIG has been developed by the Government of Valencia. Although gvSIG showed the public through its website www.gvsig.gva.es first time in 2004, his birth could be at the end of 2002 . The public tender dossier 2003/01/0090 and "Development of GIS applications for COPUT using Free Software" , calling for the implementation of a pilot project that would allow the selection of both the company and the programming language , so the pilot should be both C and Java. The winner was the company IVER Information Technologies , SA , and selected the Java language. So , the first version of gvSIG 0.2 was published in October 2004. During the development of the project have been constantly being published new versions with new features, up to the present, the gvSIG is oriented to manage geographic information and characterized by a friendly interface tool, being able to access the most common formats agile, both raster and vector, can be integrated into a view of both local and remote data. It is an open source application with free GPL ( General Public License or GPL ). It has placed particular emphasis since its inception in gvSIG is an extensible

project so that developers can extend the functionality of the application easily and develop completely new applications from the libraries used in gvSIG ( provided they meet the GPL license) .

6.2.2 REFERENCE SYSTEMS 1. INTRODUCTION When understood as holding the spatial representation of the earth's surface on a plane you need to have some clear concepts. The graphical representation of vector data that make up a GIS is always calculated according to a reference system based on this representation change the coordinate values. The sciences that study Earth representation systems are the Surveying and Geodesy. Topography is the science that studies the set of methods available to determine the position of a point on the surface of the earth , both in planimetry and altimetry, based on a framework. This framework established Geodesy, the science that deals with measuring and representing the figure and gravity field, as well as other celestial bodies and their variations over time. Geodesy is the narrow shape of the earth, and it gets two auxiliary reference surfaces, which are the geoid and the ellipsoid.

Fig 1 â&#x20AC;&#x201C; Geoid and ellipsoid on the Earth's Surface

The geoid is a geometrical figure representing the mean sea level at the surface if the water flowed beneath the continents. This is the figure that most closely approximates the actual shape of the Earth. This figure is not valid for the calculation of positions (coordinates), however if they can be considered as the reference surface altimetry. To calculate the planimetric positions ellipsoid is used, defined as the solid generated by rotating an ellipse around one of its axes. Ellipsoid parameters are chosen so that this as much as possible fits surface of the geoid. Since the geoid is an irregular figure, because of the distribution of the masses of the planet and its lack of homogeneity, is to be replaced, when you do the math mapping to use in their transformations, by a regular shape, an ellipsoid. Cartography has been looking at all times, even surfaces that best fit the surface. This search has led to different datums or "Reference Systems".

2. THE DATUM The different mathematical models to represent a specific point on a map with their coordinate values is called datum or "Reference System", which is specific to each reference ellipsoid. The datum defines therefore the reference ellipsoid and the distance between the ellipsoid and the geoid. There are global reference systems such as WGS84 (World Geodetic System 1984) and ITRF (International Terrestrial Reference Frame) and local datums, optimized for a specific region, such as the European Middle Datum 1950 (European Datum 1950) for all Europe and individual variants adjustment for countries or member groups such as the European Datum of 1950, official reference system for Spain and Portugal until 2007.

3. GEODETIC REFERENCE SYSTEM

The Geodetic Reference System Officer, currently existing in the Iberian Peninsula and the Balearic Islands is the Reference System ETRS89 (European Terrestrial Reference System 1989) and in the case of the Canary Islands REGCAN 95.

4. COORDINATE SYSTEMS

The different systems existing coordinates used in cartography we will serve to define the position of the points of the earth's surface, so that we can know the exact situation in an unambiguous way. At present, the maps using two main types of coordinate systems, and projected coordinate geographical coordinates.

Geodetic or geographic coordinates

It is mainly used for very large geographic representations - continents, globes, etc.. -, However, not be straight or have a constant pitch, these coordinates can not be reproduced in any form of projection. They are also not suitable for technical purposes as they makes the process of measuring distances, areas and directions. Geographic coordinates or geodetic coordinates can be considered as spherical coordinates: note the position in degrees and minutes (and seconds) on a spherical surface along parallel (Latitudes N and S) and meridians (Lengths W and E). It is the oldest and most universal of the

reference systems.

Fig 2 – Geographical coordinates of the Iberian Peninsula and the Canary Islands

The Iberian Peninsula is located approximately between latitudes 36 ° N and 43 ° N, and between the meridians 9 ° W and 3 ° E. The Canary Islands are located between latitudes 28 ° and 29 ° N, and meridians 14 ° and 18 ° W. Geographic coordinates are usually expressed in the sexagesimal system: Ej: 41º40’22’’ N, 4º44’2’’ W These same geographical coordinates can be expressed in a decimal system: Ej: 41.6810721406 N, -4.739410356 W

Projected coordinates

Map projections are procedures that allow us to represent the terrestrial spheroid in the plane of the map. The surface of this spheroid is not pop on a plane , so the translation is impossible without mistakes : either deform the contours of the figure projected or falsify the area of the figure . There are three types of projections : cylindrical, conical and perspectives. The main projection used in Spain is the UTM projection. The system of UTM coordinates (Universal Transverse Mercator) is based on a system of transverse cylindrical projections. It is a rectangular or metric system used in Spain since 1968 (National Geographic Institute) and 1970 (Army Geographic Service). Its great advantage is that its unit of measurement is meters , making it simple to use metrics to calculate distances. This system is divided into zones, numbered 1 to 60, each of amplitude 6 . The Iberian Peninsula and the Balearic Islands are located in

the zones 29, 30 and 31, and the Canary Islands in the 28 (and 27). In addition, each zone is divided into 20 transverse bands, numbered alphabetically from point C to point X. The Iberian Peninsula is included in the S and T bands (Canary R).

Fig 3 â&#x20AC;&#x201C; Universal Transverse Mercator in the world

Fig 4 â&#x20AC;&#x201C; Universal Transverse Mercator in the Iberian Peninsula and the Canary Islands

5. CODES EPSG

Codes EPSG (European Petroleum Survey Group) are a standardized way to encode the reference systems and projections. Each code corresponds to a reference system and a type of projection, EPSG codes these are the most used in the Iberian Peninsula: UTM projection (projected coordinates, flat or rectangular) DATUM ED 50

WGS 84

ETRS 89

Zona 28

23028

32628

25828

Zona 29

23029

32629

25829

Zona 30

23030

32630

25830

Zona 31

23031

32631

25831

Geographical coordinates DATUM ED 50

WGS84

ETRS 89

4230

4326

4258

6.2.3 MAPPING THE DATA

1. INTRODUCTION

It is useful to distinguish between data and information, as both concepts are important to achieve geographical knowledge . Firstly we would obtain the data, defined as the "concrete representation of the facts", the second stage consists in gathering this information on what might be called geographic database, in most cases, character digital. In the third phase would obtain the information, the result of an interpretive process generated by the individual who would add value to this information and finally would have the procurement of the knowledge of the phenomenon through the internalization of conceptual information and open the possibility that people to work with this information to extract conclusive reasoning. There are several sources for obtaining map data either through direct data capture from techniques such as photogrammetry or remote sensing, digitizing existing analog data gathering topographic information prepared by third parties, in most of cases public institutions. The map data is an abstraction of reality defined by elements representing the characteristics of real models based on the following components: Space Component : Data are presented in a certain position on the territory. Subject Component: data are associated with a number of key attributes when making such data analysis Temporal Component : defining time data were described

2. DATA TYPES: vector and raster

The map data can be classified into two types: vector and raster model model. Vector model: it represents geographic entities from three basic elements: points, lines and polygons. The relationships between these entities are explicitly defined by the use of topology and descriptive characteristics are characterized by alphanumeric data. Raster model: to represent each surface is divided into rows and columns, forming a regular grid. Each cell in the matrix contains the coordinates of the location as the thematic value. This is an image composed of pixels.

The cell size determines the scale of the image that is being introduced, logically the smaller the cell, the higher the resolution is obtained.

Fig 5- Representation of the vector model and the raster model

The raster-vector integration is relatively recent, were before GIS raster or vector type. Much of the current possibilities of exploitation of a GIS comes from this "new" capacity. The advantages of both formats are: ADVANTAGES VECTOR MODEL

RASTER MODEL

Easy management of your databases

The space is defined in a uniform and highly visual

Provides a compact data structure, takes up less memory

Increased analytical power in the analysis of the space

More effectively encodes the topological relationships between elements.

Faster evaluation of various mathematical problems involving combinations

Best possibilities when creating maps with great appeal

Easier to insert satellite imagery in GIS

DISADVANTAGES VECTOR MODEL

RASTER MODEL

It has a data structure more complex than raster

Requires powerful computers and a great capacity for virtual memory and hard drive

Overlay operations are more difficult to obtain

The maps are less "aesthetic", the limits are more rude. This phenomenon can be overcome by reducing the size of the pixel, but greatly increases the volume of file

The representation of maps with high variability is inefficient Management and improvement of digital images and satellite can not be done in an effective manner

3. VECTOR DATA

In the vector model geographic features from coordinate pairs or trios if the coordinate system has three dimensions are represented. With a pair of coordinates (X, Y) a point is defined by a sequence of pairs of coordinates and a line is generated with an array of closed polygons are generated lines. This type of representation supports geometric operations such as calculating lengths and areas, identification of overlaps and intersections, as well as search for entities that are adjacent or nearby. The three types of objects handled are: Points: are one-dimensional shapes that represent too small to be lines or surfaces (a well, an electric pole, etc ...) geographic entities. Are stored as simple X, Y (Z) with associated attributes. Lines: they are one-dimensional shapes that represent geographic features too narrow to define an area (axis of roads, waterways on small scales), or entities that have length but no area (contours, for example). They are stored as an ordered set of coordinates X, Y (Z) with attributes. The segments that define the lines may have different, straight, elliptical, circular, etc forms. Polygons: are two-dimensional shapes that represent geographic entities consisting of a series of segments that enclose an area (nation, land, soil types, for example)

Fig 6 - Representation of points, lines and polygons using vector structure

4. RASTER DATA

The raster model is suitable for representing spatially continuous variables (temperature, precipitation, etc. ...) in a series of discrete elements by means of layers with cells space. Each cell has associated:

- Implicitly, a value (x, y) in a coordinate system - Explicitly, the value of a variable (altitude, relative humidity, biomass, etc ...) This model can represent specific elements: a point is represented by a cell line with a sequence of cells and a polygon aligned in a grouping of contiguous cells.

Fig 7- Representation of a point, line and polygon in the raster model

Unlike the vector model, the raster model is explicit content while limits are marked implicitly.

The cell size (spatial resolution) must be in accordance with the frequency of variation of the variable to be represented, as if over the level of detail is lost. The model structure is raster matrix, ie each location is represented as a cell in an array, arranged in rows and municipalities. This structure is commonly referred as Grid. Raster types:

- Spectral: store information on the amount of energy reflected by the surface of the Earth. They are used as support for the data captured by remote sensing techniques.

- Theme: the value of each cell or pixel represents a variable. For example, in the case of a Digital Elevation Model raster will be a regular grid whose pixels contain the values of altitude.

- Photographs: are a type of raster data stored spectral reflected radiation in the visible spectrum.

5. THE SDI AND SERVICES WMS Spatial Data Infrastructures (SDI) is a set of technologies but also about a number of policies and institutional arrangements to ensure that geographic information can be distributed by the government through a series of tools and applications. Thus, initiatives such as the U.S. NSDI, INSPIRE in Europe or in Spain IDEE (developed by the National Geographic Institute ) to try to standardize the discovery and access to information produced by multiple government have emerged. The SDI is set by both networks as authentic publishing geographic information systems in many different ways but always following the same set of standards, the OGC standards , of which we have spoken above. The use of defined standards allows for integration of information from multiple sources in visual web known as geoportals . A geoportal is a web application to find information by accessing metadata servers and display it on the website itself using oriented protocols for this purpose . The Spatial Data Infrastructure of Spain (IDEE) aims to integrate the Internet data , metadata, services and geographic information type that is produced in Spain , making it easier to all potential users to locate, identify, select and access to such resources , through the IDEE geoportal (http://www.idee.es) that integrates the nodes and resources geoportals SDI producers of geographic information at national, regional and local levels and with all types of data and geographic information services available in Spain.

An SDI is conceived as a geographic information system implemented on the network, and must provide three basic services in the Commission of the High Geographic Council Geomatics: 1. Web Map Services or Web Map Service (WMS) Its aim is to visualize geographic information. Provides a representation, an image of the real world for a given area. This representation can come from a data file of a GIS, digital mapping, orthophoto, a satellite image .... It is organized into one or more layers, which can be displayed or hidden at a time. You can check out some information and the characteristics of the map image. This OGC specification allows visually overlay vector data, raster, in different format, with different reference system and coordinates and different servers. 2. Catalog Service or Catalogue Service Web (CSW) The catalog service standardizes how the metadata of all kinds of geographical information both published by other standards as any geographic resource (scanned photos, paper maps, etc ...) are published This service is the key element in a IDE to offer users the ability to find that information published different actors: companies and especially government. 3. Nomenclator service (WFS-MNE [11]) A Nomenclator service is defined as a service that returns full descriptions of geographical entities selected by consulting their identifiers. The most common use of a nomenclator service is to store a selection of real-world entities with place names that identify them, and allow a user to identify the location of the entity based on its place name. Other services that may contain an SDI are as follows: -

Feature Service or Web Feature Service (WFS) Allows access and view all the attributes of a spatial feature such as a river, a street or a city, represented in vector mode, with a geometry described by a set of coordinates. Usually the data are provided in (another standard OGC) GML format. A WFS allows not only display the information as permitted by a WMS, but also consult and download it freely.

Coverage Service or Web Coverage Service (WCS) This service provides access to raster data without postprocessing. Ie, provides access to the actual data in compressed or uncompressed and a single band or multispectral formats. This makes it possible to publish Digital Terrain Models (DTM) or by standard satellite image.

6.2.1 GEOGRAPHIC INFORMATION SYSTEMS

2. HISTORY

The 60’s

The 70’s

During this decade, the National Center for Geographic Research and Analysis (NCGIA) whose purpose was to "develop basic research on geographic analysis using GIS” was created.

Cartography

Science that deals with the study of the representation of the Earth's surface or part of it, through the use of maps, plans or charts and topographic, geodetic or photogrammetric data. Map

Remote sensing

Technique for obtaining information about a physical object or a phenomenon of the land surface without any direct contact with it.

Photogrammetry

Technique for planimetric and altimetric representation of the terrain through photographs of it obtained from an aircraft and under specific conditions.

Stereoscopy

4. Definition of GIS

5. SOFTWARE gvSIG

project so that developers can extend the functionality of the application easily and develop completely new applications from the libraries used in gvSIG ( provided they meet the GPL license) .

Fig 1 â&#x20AC;&#x201C; Geoid and ellipsoid on the Earth's Surface

3. GEODETIC REFERENCE SYSTEM

4. COORDINATE SYSTEMS

Geodetic or geographic coordinates

reference systems.

Fig 2 – Geographical coordinates of the Iberian Peninsula and the Canary Islands

Projected coordinates

Fig 3 â&#x20AC;&#x201C; Universal Transverse Mercator in the world

Fig 4 â&#x20AC;&#x201C; Universal Transverse Mercator in the Iberian Peninsula and the Canary Islands

5. CODES EPSG

WGS 84

ETRS 89

Zona 28

23028

32628

25828

Zona 29

23029

32629

25829

Zona 30

23030

32630

25830

Zona 31

23031

32631

25831

Geographical coordinates DATUM ED 50

WGS84

ETRS 89

4230

4326

4258

6.2.3 MAPPING THE DATA

1. INTRODUCTION

2. DATA TYPES: vector and raster

The cell size determines the scale of the image that is being introduced, logically the smaller the cell, the higher the resolution is obtained.

Fig 5- Representation of the vector model and the raster model

RASTER MODEL

Easy management of your databases

The space is defined in a uniform and highly visual

Provides a compact data structure, takes up less memory

Increased analytical power in the analysis of the space

More effectively encodes the topological relationships between elements.

Faster evaluation of various mathematical problems involving combinations

Best possibilities when creating maps with great appeal

Easier to insert satellite imagery in GIS

DISADVANTAGES VECTOR MODEL

RASTER MODEL

It has a data structure more complex than raster

Requires powerful computers and a great capacity for virtual memory and hard drive

Overlay operations are more difficult to obtain

The maps are less "aesthetic", the limits are more rude. This phenomenon can be overcome by reducing the size of the pixel, but greatly increases the volume of file

The representation of maps with high variability is inefficient Management and improvement of digital images and satellite can not be done in an effective manner

3. VECTOR DATA

Fig 6 - Representation of points, lines and polygons using vector structure

4. RASTER DATA

Fig 7- Representation of a point, line and polygon in the raster model

Unlike the vector model, the raster model is explicit content while limits are marked implicitly.

- Spectral: store information on the amount of energy reflected by the surface of the Earth. They are used as support for the data captured by remote sensing techniques.

- Theme: the value of each cell or pixel represents a variable. For example, in the case of a Digital Elevation Model raster will be a regular grid whose pixels contain the values of altitude.

- Photographs: are a type of raster data stored spectral reflected radiation in the visible spectrum.