Spatial Analysis and Modelling - Assignment Example

Questions:- 1. Differentiate how a network is represented in (a) vector and (b) raster data structures. Which one is more suitable for applications involving a pizza delivery system? Why? (You can state your own assumptions, if needed.) ANS: - Vector data network is more suitable than a raster model for analysing correctly defined paths. A vector data, the geometry in a network is represented by linked lines. The vector network will by now have a topological agreement, related to all elements vector model. Raster network modelling takes a completely different approach to the topological linked. Vector data is more suitable for applications involving a pizza delivery system, as the data can be represented at its matchless resolution and form without simplification. Network analysis in GIS is frequently related to finding solutions to transportation problems. In a GIS the actual world is represented by one of two spatial models, vector-based or raster based 2. Refer to figure 8.6 of the study book. Locate the optimal road choice and explain your reason by providing the resulting values of ‘resistance’ for all possible route options. Discuss why the shortest distance is not always the best distance to take when travelling from one point to another. Explain this idea using network analysis in a GIS context. ANS:-The optimal road choice starts form starting point through 101 node number to the finishing point (102 node number) network. These resulting values meaningful, that the optimal road has less time delay. One of the most vital measures that can be found around a network is the not the longest distance between pair of locations For egg:-Intersection that would lie on the shortest path between a fire station and a fire is blocked, the firemen would like to know the next shortest path to their target. 3. How does fuzzy logic different from Boolean logic in a GIS context? Provide your own example. What are the different methods/ways in defining the fuzzy membership functions? In your own words, describe the characteristics and a possible application of a sigmoid membership function. ANS:-Boolean logic uses only “And, Not, or and nor”. Whereas Fuzzy logic is a superset of usual logic, it is renowned as TRUE and FALSE values. A very best example of both Boolean and Fuzzy logic is imagining walking diagonally, the tree line from the forest into the meadows. You will recognize that there is no pointed border like a "tree line"; the change is rather smooth or soft. Figure 1: S-curve (Source: www.vac-amps.com) 4. Explain the relative strengths and limitations of distance calculations/measurements for (a) vector and (b) raster data structure. Give an example (application) where distance calculation/measurement is better implemented in vector data (rather than raster data). Draw and discuss an example of a distance calculation in raster data. ANS:-In a raster system the correctness and complicatedness of the measurement information is restricted by the size of the raster cells and the structure of the database. And in vector system the natural topology mechanically permits a range of elegant measurement operations. The river is in fact slimmer than a cell, but the entire cell can be implied as river, so the river appears wider but it is not really true. So that, the distance calculation will be incorrect. And in the vector data the river does not appear different as in actual life and the distance calculation will be not being incorrect as it in actual life. FIGURE 2 (Source: - www.ioc.unesco.org) Measuring a distance in a raster GIS involves the following formula: • For horizontal or vertical distance: Distance = cell size x number of cells • For diagonal distance: Distance = cell size x number of cells x 1.414. (1.414 is the distance between two cells in diagonal form) 6. In the GIS context, explain the meaning of the ‘smallest-scale rule’? Provide examples. What possible reason(s) can you cite for ignoring (i.e. not adopting) this rule? Explain. ANS: - The not considering of area covered, the accuracy of the project is determined by smallest practical scale. Higher accuracies from larger scales will not improve the lowest accuracy data. Initially, we cannot take this rule if we are looking for lower accuracy or obscure calculation, only we take it for view purpose. The other reason is, if we look for data which is not changing too much as geological data. 7. Spatial models can be integrated with GIS using three different strategies: loose integration, tight/close integration and fully integrated GIS system. Briefly explain each of them. Discuss why loose integration strategy is most often adopted in practice. ANS: - The three levels of ‘coupling’ or “integration” are as follows: 1. Loose integration: This integration uses file exchange system where GIS and models are linked. 2. Tighter integration: This integration exchanges file with a common user interface and user-transparent. 3. Fully integrated GIS system: This integration uses common tile structure with shared memory. Loose integration strategy is often taken in practice, because loose integration uses very common and simple language programming which helps us to keep loose integration simple than tighter and full integration which not a lower level language used. The loose coupling is supple and a large number of models can be integrated. As, the cost of loose integration also, plays very important role of espouse loose than others which are not very cheap and is more expensive. 8. Refer to Selected Reading 6 The Most Beautiful Formulae in GIS, by Water (1995). If you are working on a site suitability assessment for an airport location, which three of the ten spatial formulae will you use most? Provide your own assumptions, if needed. ANS: To know the recovery time of GIS analysis for time and space recovery of the system, Kobe Water Bureau proposed a formulae. Now presently GIS includes distribution of pipe lines, damage sites, damaged sites of transmissions. 1. The initial spatial formula is the not new of all of them. The analyst uses this formula to advise the optimum allocation for a facility, such as a fire station or a fast food restaurant in the airport. Location allocation modelling is one of the most useful applications of GIS. 2 The other spatial formula is the Intersection of Two Lines. The analyst uses this formula to help for choose an area far-away of residential areas, hospitals and colleges, etc by using buffering around airport. 3 The final spatial formula is Estimating Slope and Aspect. The analyst uses this formula of estimating the slope and aspect, and airport have to be on a flat area. To know the recovery time of GIS analysis for time and space recovery of the system, Kobe Water Bureau proposed a formulae. Now presently GIS includes distribution of pipe lines, damage sites, damaged sites of transmissions. 5. Discuss the key problems and issues associated with the accuracy (related to location, distance and area) of raster data. Illustrate the concepts by using your own diagrams. How can you avoid or minimise the problem(s) that may arise in measuring area using a raster data? ANS:- The actual real world distance between two features in adjacent cells can very significantly, either very close together, to the outside edges of the cell, or even to opposite slanting corners. Uncertainty does not become so lower when measuring across cell. However, the raster distance is two cells because the cell is the smallest amount measuring unit. The other problem is area capacity; area size is also generalized. A display measure of one cell unit is shown. The standard triangle measures some square units, but requires some cells in this low resolution raster format. The amount of error can be reduced by extensively not a lower resolution. There is also a problem in measuring distance between horizontal and sloping cells. Definite distance between the centres of slanting cells is 1.4 times that of horizontal or vertical distance. However, because distance calculation in raster is based on cell count, the distance either horizontally or diagonally is reported simply as two cells. If the cell is 1 km on a side, the distance is noted as 2 km, but the real ground distance could be 2.8km. This variation and inexactness could enlarge if the there are hundreds to thousands of cell occupied. REFERENCES:- 1. www.vac-amps.com. October 17, 2007. < http:\ www.vac-amps.com.html > 2. www.ioc.unesco.org. October 17, 2007. < http:\ www.ioc.unesco.org.html > 3. Advancing Mitigation Technologies and Disaster Response for Lifeline Systems - page no 39. 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