Raster Analysis: Zonal Functions Quiz
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Questions and Answers

What defines zones in raster analysis?

  • Zones are based on specific attributes (correct)
  • Zones are always contiguous
  • Zones can only exist within one layer
  • Zones are flexible and do not require any attributes

    • Which of the following operations is typically associated with zonal functions?

  • Generating area calculations for the entire raster
  • Analyzing neighborhood influence
  • Assigning unique values to groups of cells (correct)
  • Calculating global statistics

    • In raster analysis, which function exclusively treats the entire raster as a single unit of analysis?

  • Focal Functions
  • Local Functions
  • Zonal Functions
  • Global Functions (correct)

    • What is one limitation of calculating area and perimeter in zonal functions?

    <p>Less accurate for irregular shapes unless aligned with raster orientation</p> Signup and view all the answers

    Which of the following is an example of a calculation performed in zonal statistics?

    <p>Summarizing attribute values for specific zones</p> Signup and view all the answers

    What is a primary feature of map algebra?

    <p>It integrates various raster operations for complex analyses</p> Signup and view all the answers

    Which of the following best describes a local function in raster analysis?

    <p>Depends only on the value of the same cell in input layers</p> Signup and view all the answers

    What type of function would use tools like the raster calculator in ArcGIS?

    <p>Map Algebra</p> Signup and view all the answers

    What is the primary purpose of zonal functions in raster analysis?

    <p>To operate on groups of cells treated as single units</p> Signup and view all the answers

    Focal functions depend exclusively on the same cell in one or more input layers.

    <p>False</p> Signup and view all the answers

    What is one method used for parceling in zonal functions?

    <p>Reclassification or converting polygons to rasters</p> Signup and view all the answers

    Zonal statistics calculations may include determining the ______ area.

    <p>land cover</p> Signup and view all the answers

    Match the following types of raster functions with their descriptions:

    <p>Local Functions = Depend on the same cell in input layers Focal Functions = Depend on neighboring cells Zonal Functions = Operate on groups of cells treated as single units Global Functions = Applies to the entire raster as a single unit</p> Signup and view all the answers

    Which operations can be performed using map algebra?

    <p>Combines local, focal, zonal, and global operations</p> Signup and view all the answers

    Global functions are typically used for analyzing individual cells in a raster.

    <p>False</p> Signup and view all the answers

    What computation method can be used in zonal statistics?

    <p>Mean, maximum, or standard deviation</p> Signup and view all the answers

    Calculating area and perimeter in zonal functions is less accurate for ______ shapes.

    <p>irregular</p> Signup and view all the answers

    Which of the following best describes global functions?

    <p>They apply to the entire raster as one unit.</p> Signup and view all the answers

    Study Notes

    Raster Analysis: Zonal and Global Functions

    • Raster functions categorize operations based on how they process cells
    • Local functions: New cell values depend on the same cell in one or more input layers.
    • Focal functions: New cell values depend on neighboring cells.
    • Zonal functions: Operate on groups of cells (zones) treated as single units.
    • Global functions: Treat the entire raster as one unit of analysis.

    Zonal Functions

    • Definition of Zones: Homogeneous areas based on specific attributes; zones can be connected or unconnected.
    • Basic Operations:
      • Parceling: Assigns unique values to clusters of cells with similar attributes.
      • Reclassification: Conversion from polygon to raster layer to achieve zone identification
      • Example: Assigning unique values to different bodies of water like lakes in a raster.
    • Area & Perimeter Calculations:
      • Calculates the area and perimeter of zones based on the cell dimensions in the raster
      • May be less accurate for irregular shapes, if raster resolution doesn't align perfectly with the shapes.
      • Calculations less accurate if zone shapes don't align with the raster orientation.
    • Zonal Statistics: Calculations like mean, maximum, or standard deviation per zone.
      • Analysing specific attribute values within each zone
      • Examples include finding land cover area per zone or analysing attribute values within a zone. This includes calculations like mean, maximum, minimum and standard deviation.

    Global Functions

    • Operate on the entire raster as a single unit.
    • Examples: Calculating global statistics like mean, maximum, or standard deviation for the whole dataset.
    • Found in software like ArcGIS.

    Map Algebra

    • Combines different kinds of functions (local, focal, zonal, global) for complex analyses.
    • Works by using tools like Raster calculator in ArcGIS software.
    • Example: Combining focal statistics from one layer with local operations on another.

    Key Takeaways

    • Understanding the differences between local, focal, zonal, and global functions is crucial.
    • Zonal and global operations are important for real-world applications and often serve as inputs for further analysis.
    • Mastery of these concepts enables effective use of GIS tools like ArcGIS in different situations.

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    Related Documents

    GIS Lecture Notes - Raster Analysis

    Description

    Test your knowledge of raster analysis with a focus on zonal functions. This quiz covers the definitions, basic operations, and calculations related to zones in raster data. Challenge yourself with questions about local, focal, zonal, and global functions.

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