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How are filters used for reclassification process?
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GEOG 287 MidTerm
COCC GIS Analysis Midterm
| Question | Answer |
|---|---|
| What are filters? | Apply algorithmic functions to recalculate cell values based on type filter applied. |
| How are filters used for reclassification process? | Apply algorithmic functions to recalculate cell values based on given inputs (edge detection, fragmentation, steepness of slope). |
| What’s the difference between static and roving window filters? | *Static = Block Function (whole Neighborhood) *Roving = Focal Functions (looks at each Kernel makes an evaluation, and moves on to next Kernel) |
| What are higher-level objects? | Important to the computer to understand x, y coordinates (Nodes). Importance for a future evaluation. |
| Give two examples of higher-level objects for each of the following feature classes: Points, Lines, Polygons | *Points- Centroid, Node *Lines- Edge, Borders, Networks *Polygons- Regions (multi-part), Island |
| Explain why the analysis piece of GIS is often the most abused aspect and give an example to support your explanation. | *People not applying the right tools or evaluating the data to know if outputs make sense. *An example is using Jenk’s Natural breaks as the default classification, although the data may not be normalized for natural breaks, |
| What is slope? | Rate of Change as you move through space |
| How is slope implemented in a vector data model? | Using TIN- Triangular irregular networks (TIN) functions |
| How is slope implemented in a raster data model? | Using a Filter, roving window of the neighborhood. |
| What are Map Algebra functions? | * Formulating command statements that perform cartographic analysis. Creates new grids * Raster Calculator tool contains the functions and is used to perform them |
| Name, explain and give an example of Local functions | *Looks at single cell/kernel. The value in the output is contingent only on the input cell at that location. * An example: Highest Position (conditional finds the highest point) |
| Name, explain and give an example of Focal functions | *Classifies per neighborhood. Output value results from neighborhood of the input. * An example is: Focal Statistics |
| Name, explain and give an example of Global functions | *Evaluates the entire grid. *An example: high/low value |
| Name, explain and give an example of Block functions | *Aggregates neighborhoods to evaluate a value as a block. Blocks don't overlap, value in block computed and written to all cells of the block. * Example Block Statistics-Mean (finds the mean of each neighborhood) |
| Name, explain and give an example of Zonal functions | *Evaluates value Per zone. All output cells get the same value. *An example is Zonal Area |
| What are the four basic reasons used to define a buffer distance? (I.E. what drives you to establish a buffer distance of 50?) Describe them. | * Arbitrary - random * Causative – function about what is going on, movement * Measureable – measuring out (or in) from a feature for informational purposes * Mandated – buffer given by organization |
| Provide two methods to measure dispersion of a set of data. Explain each. | * Range = Highest – lowest value. Shows the spread of the values * Standard deviation = the average difference between frequencies |
| Give an example of a simple reclassification that aggregates two or more classes together into single class. | * Reclassify slopes: 0-10 degrees = 1, 10-20 = 2, etc to a new value |
| What is intervisibility analysis? | Determines what you can see from a location (cell) |
| What is a viewshed? | Output of what you can see in intervisibility analysis |
| How does one calculate a viewshed in vector? | Using TIN- Triangular irregular networks (TIN) functions |
| How does one calculate a viewshed in raster? | Using the extended neighborhood function |
| Describe some uses of intervisibility analysis. | LOS for fire watch tower, location of cell tower |
| What is the purpose of Euler numbers? | To measure the degree of fragmentation as the amount of perforation |
| What factors influence a feature having a particular Euler number? | Number of Holes and Fragments |
| Why is it important to be able to isolate, identify, count and separately tabulate and display individual items? | First Steps in order to perform analysis |
| When measuring the distance between two features one could use âsimple distanceâ Explain what that means. Give Examples. | Simple Distance (Euclidian) is a straight line, regardless of barriers or impedance, direction and cost. o Euclidean/isotropic o Straight line distance o Doesnât matter the direction you measure * No factors adding to cost of movement |
| When measuring the distance between two features one could use âFunctional distanceâ Explain what that means. Give examples. | Functional Distance is a distance based on path, in one direction, with the least calculated cost. o Anisotropic o Measures in a specific direction o Least cost paths * Slope, friction, barriers, etc |
| What are some similarities and differences from simple and functional distance? | *Similarities: Both try to determine a distance between two points. *Differences: Euclidian simple straight line regardless of barriers or impedance. Functional determines the best path best on cost inputs. |
| What is absolute frequency? | Absolute values within a dataset |
| What is Relative frequency? | Relative Frequency is the percentage of the values |
| What is/are the dimensions associated with points, lines and polygons? | *Point-zero, none *Line-one, length *Poly- two, length and width |
| What are three different measurements you could make on a line feature? | *Sinuosity *Length *Orientation |
| What are three different measurements you could make on a polygon feature? | *Area *Perimeter *Angles |
| What is the main difference between an isotropic and an anisotropic surface? | Direction. We use Isotropic (example walking up and down a hill, use same cost value) |
| What are the differences between a Bar Chart and a Histogram? | Bar charts represent Qualitative categories not contiguous (touching bars) Histogram represents Quantitative Continuous Numeric values of a single category (Bars must touch) |
| Make sure to review graphic of categorical distribution types (was on test). | *Top left-Natural Breaks *Top right- Algorithimic progression *Bottom left- Standard Deviation *Bottom right- Equal or Quantil Interval |
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Sevcav
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