Vector And Raster Data In Gis Computer Science Essay

Vector And Raster Data In Gis Computer Science Essay A Geographical Information System (GIS) is a method of spatially storing, analysing, manipulating, managing and displaying geographical data. GIS data represents real objects such as roads, rivers, urban areas, place names, railway, places of interest, town names etc. with digital data determining the mix. A geodatabase is a database that is in some way referenced to locations on earth. Traditionally, there are two broad methods used to store data in a GIS; raster images and vector. Ordnance Survey Ireland (OSI) data is supplied in both Vector and Raster format. In both cases the data is geo-referenced. VECTOR AND RASTER DATA Vector data is split into three types; polygon, line (or arc) and point data. Vector is a method for storing spatial data involving assigning coordinates for each entity; an X,Y, Z for a point, a pair of such points for a line and a series of such lines for a polygon. This method is very useful for modeling discrete physical features. Different geographical features are expressed by different types of geometry: Points A point is a zero-dimensional abstraction of an object represented by a single X, Y co-ordinate. It is normally used to represent a geographic feature too small to be displayed as a line or an area (e.g. location of a building on a small scale map or, for example, cities on a map of the world might be represented by points not polygons). No measurements are possible with point features. Figure 1- Vector representation Source: http://www.geom.unimelb.edu.au/gisweb/GISModule/GIST_Vector.html Lines or polylines A set of co-ordinates that represent the shape of geographic features that are too narrow to be displayed as an area, such as, county boundary lines or contours. At small scales geographic features may have no area, e.g. streams or streets and may be represented as linear features rather than as a polygon. Line features can measure distance. Polygons Polygons are used to represent areas. Such as lakes, park boundaries or land uses etc. Polygons convey the most amount of information of the file types and can measure perimeter and area. Rigaux et al. (2002:p.38) states, A point is represented by its pair of coordinates, whereas more complex linear and surfacic objects are represented by structures (lists, sets, arrays) on the point representation. These geometries can be linked to a row in a database that describes their attributes. For example, a database that describes lakes may contain a lakes depth, water quality, pollution level. Different geometries can also be compared and the GIS could be used, for example, to identify all wells (point geometry) that are within one kilometre of a lake (polygon geometry) that has a high level of pollution. Vector data can be displayed at any scale and individual layers (e.g. roads, buildings, etc) can be displayed or omitted (see Appendix A). Raster Ellis states that raster is a method for the storage, processing and display of spatial data. There are three types of raster datasets; thematic data, spectral data and pictures. Raster data consists of rows and columns of cells, with each cell storing a single value. Raster data can be images containing individual dots with colour values, called cells (or pixels), arranged in a rectangular evenly spaced array. Each cell must be rectangular in shape, but not necessarily square (Ellis 2001). Each cell within this matrix contains location co-ordinates as well as an attribute value. The spatial location of each cell is implicitly contained within the ordering of the matrix, unlike a vector structure which stores topology explicitly. Areas containing the same attribute value are recognised as such, however, raster structures cannot identify the boundaries of areas such as polygons. Raster data is an abstraction of the real world where spatial data is expressed as a matrix of cells or pixels with spatial position implicit in the ordering of the pixels. With the raster data model, spatial data is not continuous but divided into discrete units. Ellis states that this makes raster data particularly suitable for certain types of spatial operation, for example overlays or area calculations. Raster structures may lead to increased storage in certain situations, since they store each cell in the matrix regardless of whether it is a feature or simply empty space. Additional values recorded for each cell may be a discrete value, such as land use, a continuous value, such as temperature, or a null value if no data is available. While a raster cell stores a single value, it can be extended by using raster bands to represent RGB (red, green, blue) colours, colour maps (a mapping between a thematic code and RGB value), or an extended attribute table with one row for each unique cell value. The resolution of the raster data set is its cell width in ground units. Anyone who is familiar with digital photography will recognize the Raster graphics pixel as the smallest individual grid unit building block of an image, usually not readily identified as an artifact shape until an image is produced on a very large scale (see Appendix B). A combination of the pixels making up an image colour formation scheme will compose details of an image, as is distinct from the commonly used points, lines, and polygon area location symbols of vector graphics. Aerial photographs and satellite images are examples of raster images used in mapping. Figure 2 Aerial Photo Digitally scanned and ortho-rectified raster colour photography. The ortho-rectification process removes distortions caused by camera tilt and topographical features to produce a scale accurate image. Source: OSI Raster data is stored in various formats; from a standard file-based structure of TIF, JPEG, etc. to binary large object data stored directly in a relational database management system. Raster v Vector There are some important advantages and disadvantages to using a raster or vector data model to represent reality: Vector graphics are usually more aesthetically pleasing. Raster data will appear as an image that may have a blocky appearance for object boundaries (depending on the resolution of the raster file). Vector data is simpler to update and maintain, whereas a raster image will have to be completely reproduced (e.g. a new road is added). Vector data allows much more analysis capability, especially for networks such as roads, rail, telecommunications etc. Distances and areas can be calculated automatically. With raster data it is difficult to adequately represent linear features depending on the cell resolution. Therefore, network linkages are difficult to establish. Vector files require less disk storage space than raster data. Raster data allows easy implementation of overlay operations, which are more difficult with vector data. Raster data structure allows simple spatial analysis procedures An outline of the application of vector and raster data by OSI in Ireland is included in Appendix C. Non-spatial data Relating the spatial component along with the non-spatial attributes of the existing data e.g. census figures (see Appendix D) enhances the users understanding and gives new insights into the patterns and relationships in the data that otherwise would not be found. Non-spatial data can be stored along with the spatial data represented by the coordinates of vector geometry or the position of a raster cell. In vector data, the additional data contains attributes of the feature. In raster data the cell value can store attribute information, but it can also be used as an identifier that can relate to records in another table. Software is currently being developed to support the solutions to spatial problems being integrated with solutions to non-spatial problems. This will result in non experts using GIS to integrate spatial and non spatial criteria to view solutions to complex problems and to assist in decision-making. Data capture The processes of data collection are also variously referred to as data capture, data automation, data conversion, data transfer, data translation, and digitizing. The two main types of data capture are: Primary data sources e.g. those collected in digital format specifically for use in a GIS project. Secondary sources, digital and analog datasets that were collected for a different purpose and need to be converted into a suitable digital format for use in a GIS project. For vector data capture the two main branches are ground surveying and GPS. Survey data can be directly entered into a GIS from digital data collection systems on survey instruments. Positions from a Global Navigation Satellite System like Global Positioning System (GPS), another survey tool, can also be directly entered into a GIS. New technologies allow creating maps as well as analysis directly in the field and as a result projects are more efficient and mapping is more accurate. Remotely sensed data also plays an important role in data collection and consists of sensors (e.g. cameras, digital scanners) attached to a platform which usually consist of aircraft and satellites. The majority of digital data currently comes from photo interpretation of aerial photographs. Workstations are used to digitize features directly from stereo pairs of digital photographs. These systems allow data to be captured in two and three dimensions, with elevations measured directly from a stereo pair using principles of photogrammetry. Photographs are collected by analog or optical cameras before being entered into a soft copy system, but as high quality digital cameras become cheaper this step will be eliminated. Satellite remote sensing provides another important source of spatial data. Remote sensing collects raster data that can be further processed to identify objects and classes of interest, such as forested areas. The disadvantages are that the resolution is often too course or sensors are restricted by cloud cover. Entering data into GIS usually requires editing, to remove errors, or further processing. For vector data it must be made topologically correct before it can be used for some advanced analysis. For example, in a road network, lines must connect with nodes at an intersection. For scanned maps, blemishes on the source map may need to be removed from the resulting raster. To ensure that the data is specific and reliable and that represents as closely as possible the spatial world we live in, it requires a quality insurance process to manage completeness, validity, logical consistency, physical consistency, referential integrity and positional accuracy of data. Raster-to-vector translation Vectorisation is the process of converting raster data into vector data. For example, a GIS may be used to convert a satellite image map to a vector structure by generating lines around all cells with the same classification, while determining the cell spatial relationships. One of the biggest problems with data obtained from external sources is that they can be encoded in many different formats. Many tools have been developed to move data between systems and to reuse data through open application programming interfaces. Therefore, a GIS must be able to convert geographic data from one structure to another. CONCLUSION When data is captured, the user should consider if the data should be captured with either a relative accuracy or absolute accuracy, as this could not only influence how information will be interpreted but also the cost of data capture. Vector data can be manipulated, layers can be turned on and off, data can be edited or deleted and additional data can be added in. Raster data is usually used as a background map. Raster is not as intelligent as Vector, Rigaux et al. (2002: p.39) states the structure is unfortunately not powerful enough to ensure the correctness of the representation. It is more useful as a display map for brochures, internet and power point presentations. Oosterom Van, P.J. (1993:p.vii) states the ever increasing availabilitiy of hardware such as digitizers, scanners workstations, graphic displays, printers and plotters for the input, processing, and output of geographic data only partly explains the growing interest in GISs. GIS allows us to view, understand, question, interpret, and visualise data in many ways that reveal relationships, patterns, and trends in the form of maps, globes, reports, and charts. GIS helps one answer questions and solve problems by looking at data in a way that is quickly understood and easily shared. Figure 3 GIS continues to evolve Source: Cummens 2010 ERSI Many forces are converging transforming how we work and improving efficiency and decision making (see Fig. 3 above). GIS Is becoming Mainstream Technology going beyond focused applications (Cummens 2010). GIS is helping citizens, business and Government by improving planning, management, communications and decision making. REFERENCES Cummens, Patricia (2010) Geographic Information Enabling a Smarter Government and Economy at the SCS Conference 2010. ESRI. Ellis, F. (2001) Introduction to GIS. Melbourne: University of Melbourne. Oosterom Van, P.J. (1993) Reactive Data Structures for Geographic Information Systems. New York: Oxford University Press. Rigaux, P., Scholl, M., Voisard, A (2002) Spatial Databases with Applications to GIS. San Fransisco: Morgan Kaufmann Publishers. http://www.osi.ie/en/academic/third-level-and-academic.aspx?article=4bf958eb-bf0b-4b28-a0d9-24586fadbaab Accessed 27/10/2010

The Writitng of Ambrose Bierce Essay -- Papers Writing Style Amrbose B

The writing style of Ambrose Bierce can simply be described as bitter. Almost all of his stories had some sort of irony or plot twist that made his stories interesting. Events in his life have shaped his view on the world. This viewpoint extends into his writing when he looks at the bitter side of the world in most of his stories and also the aspect of death. In the stories An Occurrence at Owl Creek Bridge and A Watcher by the Dead, he uses irony and examines death. Along with his patented irony, Bierce uses death in many of his popular stories, possibly as a wish for himself. His lonely and tragic life caused him to be the bitter writer we know today. Ambrose Gwinett Bierce was born on June 24, 1842 in a log cabin in Meigs County, Ohio. He was the youngest of nine children and was born into a poor family with an odd father. Bierce did not enjoy his childhood and ended up hating his entire family except for one brother. His preference for aristocratic heroes probably came from his troubled childhood and class status. His future bitterness may have come from the difficulties he had when he was a child (Fadiman XI). Before he started his writing career Bierce served in the army during the Civil War, first as a drummer boy. By then end of the Civil War he was promoted to the rank of lieutenant, being wounded only once in the war. There is no evidence that he agreed with the aims of the North, but there is some evidence that he sided more with the aristocratic planter culture of the South. While he was in the army, Bierce was considered a man that possessed qualities of leadership that promoted him through the ranks. Bierce joined the war at a very young age, and seeing the worst of mankind of that time could hav... ...his experiences with the elite of San Francisco. He always hated the way he was brought up and how he was poor as a child. Many of his stories use characters that are opposite of how his childhood in reality was, in order to create a false past. All of his stories used at least one of these aspects (Epstein 87-89) Ambrose Bierce can be considered one the greatest cynics of all time. It is obvious that the events in his life caused him to be the bitter, cynical person we see in his stories. In an article relating to how Ambrose Bierce started the cynical, ironic writing in America, Joseph Epstein says, â€Å"If the Civil War may be said to have put the blackening on Bierce’s outlook, his career in journalism supplied the polish (Epstein 86).† Every event in his life, from his troubled youth, to his Civil War experience, led him to the writer he is known as today.

Internet Does Harm Than Good

The Internet is a web that connects all the computers in the world. It's a good way to connect with people; without the internet people can lose their connections. For me the internet doesn't bring any harm to the world. In contrary with it the people move much faster in every way. Instead i think that is the people that use it are the ones that bring harm to the world . Not only the people but the way they use it. People bring cyber bullying, murders, verbal harm and more to the Internet.In my school there was a case of cyber bullying were one person did an account on facebook; this person put a random name and started insulting people. My grade started to be more away from each other; there were more little groups of people than before. This shows how via the Internet a person broke the unity of a group of people. I do believe The Internet brings more harm than good. There are a lot of people connecting but there is also millions of cases of people being harmed on the Internet. )Th e Internet's definition by wikipedia is a â€Å"network of networks†. The Internet has brought a lot of good points, but as with any tool, I would like to add that misuse has made the Internet bad. Remember, the Internet is a useful tool, but all that glitters is not gold. Firstly, the Internet is a place which is NOT safe for children. This is basically because of threats of pop-ups, pornography and scams that can trick the child. The Internet is not only an unsafe place for children, but also a bad influence to young teenagers.Pornography from the Internet is leading to the rise of a society of perverts, paedophiles and freaks, who are unable to contain their sexual desires. The number of rape cases this year in Malaysia alone has shocked officials and even the Prime Minister. Teenagers are the group targeted by the Internet. 28% of teenagers globally watch pornography. This might be a minority of people, but the way Internet has affected us in such a way is shocking. The b ad effect on the younger generation, our future leaders, is undeniable.Do keep in mind that the presence of â€Å"net-nannies† and safesearch programs does not deter our children as 20% of the so called â€Å"bad† side of the Internet is overlooked by safesearch programs. However, 10% of non-harmful content such as â€Å"breast cancer† on the internet is filtered by the safesearches used to deter pornography. 3)Harm – Visiting inappropriate site. – Involved with E-Bullying. – Privacy is being compromised by the ever increasing storage of personal data on servers. – The Internet can be used for crime as well as legal activities.

Renaissance Beauty and Art essays

Renaissance Beauty and Art essays Renaissance Beauty as Portrayed Through Artwork Donatellos bronze David is a paramount example of Renaissance beauty as portrayed through art. Donatello was one of the most important and influential fifteenth century masters. His bronze rendition of David was an enigma that was unlike Donatellos, or any of his predecessors prior works. It differentiated in its style, which incorporated a new use of aesthetics that had not been seen since antiquity, and also strayed from the idea that the human body was the wellspring of sin. Though the sculpture can be seen as beauty in the grotesque, with foot propped atop Goliaths severed head, the whole nature of David is tame, unthreatening, even homoerotic. Donatellos uses the natural form of contrapposto, shows life like anatomy of the human form, and adds a hint of romantic charm which lies in the hat on Davids head, showing the Renaissance influence on a biblical legend. Vasario said that Donatellos David is a sculpture whose figure is so natural in its vivacity, and in the softness of the flesh, that it seems to the artificers as though it must be cast from life. David is unlike any sculpture before that time for that exact reason. As his works are examined, David stands out simply for its classical style, which was not the usual style of sculpting. Donatellos bronze David is a magnificent celebration of the beauty of the male form, and an immaculate portrayal of Renaissance beauty as portrayed through artwork. ...

What a Fulgurite Is and How To Make One

What a Fulgurite Is and How To Make One The word fulgurite comes from the Latin word  fulgur, which means thunderbolt.  A fulgurite or petrified lightning  is a glass tube formed when electricity strikes sand. Usually, fulgurites are hollow, with a rough exterior and smooth interior. Lightning from thunderstorms makes most fulgurites, but they also form from atomic blasts, meteor strikes and from man-made high voltage devices falling onto the ground. Fulgurite Chemistry Fulgurites typically form in sand, which is mostly silicon dioxide. The melted sand forms a glass that is called lechatelierite. Lechatelierite is an amorphous material that is considered to be a mineraloid, similar to obsidian. Fulgurites come in a range of colors, including translucent white, tan, black and green. The coloration comes from impurities in the sand. Make a Fulgurite - Safe Method Fulgurites occur naturally, but there are a couple of ways you can make petrified lightning yourself.  Dont put yourself at risk of a lightning strike! The best way to make a fulgurite is to be safely indoors when its stormy outside. Check the weather forecast to find out when lightning activity is expected. Radar is good or refers to special maps for your area that record lightning strikes. You must complete preparation for a fulgurite several hours (or longer) before the storm arrives.Drive a lightning rod or length of rebar into the sand about 12 inches to 18 inches and extending up into the air. You can set up colored sand or some granular mineral besides quartz sand if you prefer. There is no guarantee lightning will strike your lightning rod, but you improve your chances if you select an open area where the metal is higher than the surroundings. Choose an area far from people, animals or structures.When lightning approaches, be far away from your fulgurite project! Do not check on whether you make a fulgurite until several hours after the storm has passed.The rod and sand will be extremely hot after a lightning strike. Use care when checking for a fulgurite so that you dont burn yourself. Fulgurites are fra gile, so dig around it to expose it before removing it from the surrounding sand. Rinse excess sand with running water. Rocket Fulgurites You can go the Ben Franklin route making a fulgurite by drawing the lightning down to a bucket of sand. This method involves launching a D model rocket toward a thunderhead that is estimated to be due to discharge. A spool of thin copper wire connects the bucket to the rocket. While said to be quite successful, this method is extraordinarily dangerous because the lightning doesnt just follow the wire back to the bucket. It additionally follows the wire and the area around it back to the trigger used to launch the rocket... and you! Simulated Lightning Fulgurites A safer, though someone expensive method, is to use an xfmr or transformer to force man-made lightning into silica or another oxide. This technique fuses the sand into lechatelierite, although it is much more difficult to achieve the branched effect seen in natural fulgurites.

Direct advertising Dissertation Example | Topics and Well Written Essays - 3000 words

Direct advertising - Dissertation Example Literature Review Direct Advertising There is a clear need for highly targeted marketing activities within the Internet environment. The Internet is a collection of smaller submarkets where developing and maintaining relationships with online customers generates sales, regenerates sales and subsequently profits (Norwood et al. n.d). However, applying this kind of marketing approach is not as simple as it looks. The online marketers may understand that marketing online only includes one-to-one promotion. The difficulty may be that the statistical data of the online consumers do not favour relationship building: 88 percent own a home computer and 67 percent of Internet newcomers are male, 39 percent have a college degree and 17 percent live in householders with only incomes of $ 80,000 or more (Norwood et al. n.d). Moreover, the reports suggest that the online consumers could be identified as impatient, having no particular allegiance to any particular websites. And more specifically, the on line users can be described as ‘switchers’, empowered to choose which site they want to visit so that when encountered with a barrage of on-line advertising, they simply switch to another website. This could subsequently be said that the on-line consumer may not prefer to enter into a relationship. In addition to that, there is a strong perception that a considerable number of online users and consumers believe that they the promotions through direct advertising cannot be relied as the frequency of fraud cases have enhanced to a dangerous level. Given these circumstances, the task of constructing and maintaining long term on line relationships has become a biggest challenge ever faced by the marketers. The key is to secure customer loyalty which would... This "Direct advertising" essay outlines the usefulness of this type of ad for companies and its effectiveness. Applying this kind of marketing approach is not as simple as it looks. The online marketers may understand that marketing online only includes one-to-one promotion. The difficulty may be that the statistical data of the online consumers do not favour relationship building: 88 percent own a home computer and 67 percent of Internet newcomers are male, 39 percent have a college degree and 17 percent live in householders with only incomes of $ 80,000 or more. The reports suggest that the online consumers could be identified as impatient, having no particular allegiance to any particular websites. And more specifically, the online users can be described as ‘switchers’, empowered to choose which site they want to visit so that when encountered with a barrage of on-line advertising, they simply switch to another website. This could subsequently be said that the on-lin e consumer may not prefer to enter into a relationship. In addition to that, there is a strong perception that a considerable number of online users and consumers believe that they the promotions through direct advertising cannot be relied as the frequency of fraud cases have enhanced to a dangerous level. Given these circumstances, the task of constructing and maintaining long term on line relationships has become a biggest challenge ever faced by the marketers. The key is to secure customer loyalty which would bring increased shareholder value and asset efficiency.

Management principle Essay Example | Topics and Well Written Essays - 750 words

Management principle - Essay Example Leadership is essential in management as it spells out a clear vision that others work towards and formulates the strategies of realising that dream. Management can only be easy and effective if people work together and have the same purpose (Bolman, 2013:78). Efficiency holds time and task into consideration as activities in the organisation are undertaken while effectiveness focuses more on the impact of the activity or the result it has yielded. Efficiency is all about the cost and process under which the task was operated while effectiveness is about the result the activity has produced. In the modern society it would be better for an organisation if it can have both efficiency and effectiveness in its operations but if both can’t be achieved the ‘effectiveness’ is much preferred. This is because in these modern times no one would want to rush things over and end up with a poor result. It would rather be a little bit slow but produce real results. Saving cost should only be if the result is guaranteed and that the reason why technology is expensive but it guarantees good results (Chermack, 2011:55). Centralisation and decentralisation are two opposing business structures based on power to make decisions. In centralised organisations, directives and decisions to the conduct and activities in that organisation are made by a single individual probably the business proprietor like in tiny business while decentralisation is the vesting of power to make decisions and provide management directives on different people in the company such as the departmental managers among others (Chermack, 2011:44). This structural outline varies depending on the business or company. Formal planning is the clearly lucid and well thought-out and prepared ideas about individual or organisational objectives and precisely spelt out methods and procedures of achieving them