COCC GIS Analysis Midterm
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| What are filters? | Apply algorithmic functions to recalculate cell values based on type filter applied.
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| How are filters used for reclassification process? | Apply algorithmic functions to recalculate cell values based on given inputs (edge detection, fragmentation, steepness of slope).
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| 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)
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| What are higher-level objects? | Important to the computer to understand x, y coordinates (Nodes). Importance for a future evaluation.
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| 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
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| 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,
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| What is slope? | Rate of Change as you move through space
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| How is slope implemented in a vector data model? | Using TIN- Triangular irregular networks (TIN) functions
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| How is slope implemented in a raster data model? | Using a Filter, roving window of the neighborhood.
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| 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
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| 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)
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| 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
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| Name, explain and give an example of Global functions | *Evaluates the entire grid.
*An example: high/low value
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| 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)
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| 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
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| 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
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| 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
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| 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
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| What is intervisibility analysis? | Determines what you can see from a location (cell)
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| What is a viewshed? | Output of what you can see in intervisibility analysis
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| How does one calculate a viewshed in vector? | Using TIN- Triangular irregular networks (TIN) functions
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| How does one calculate a viewshed in raster? | Using the extended neighborhood function
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| Describe some uses of intervisibility analysis. | LOS for fire watch tower, location of cell tower
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| What is the purpose of Euler numbers? | To measure the degree of fragmentation as the amount of perforation
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| What factors influence a feature having a particular Euler number? | Number of Holes and Fragments
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| 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
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| 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
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| 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
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| 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.
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| What is absolute frequency? | Absolute values within a dataset
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| What is Relative frequency? | Relative Frequency is the percentage of the values
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| What is/are the dimensions associated with points, lines and polygons? | *Point-zero, none
*Line-one, length
*Poly- two, length and width
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| What are three different measurements you could make on a line feature? | *Sinuosity
*Length
*Orientation
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| What are three different measurements you could make on a polygon feature? | *Area
*Perimeter
*Angles
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| 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)
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| 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)
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| 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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