GIS

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Author:
ichiban2008
ID:
180498
Filename:
GIS
Updated:
2012-10-29 01:22:47
Tags:
GIS
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Description:
GIS Test 2 Missed Questions
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  1. NSDI
    National Spatial Data Infrastructureshares data through clearinghouses
  2. Geometric Transformation

    3 Steps
    • Step 1: update control points to real-world coordinates.
    • Step 2: use control points to run an affine xformation.
    • Step 3: create output by applying xformation equations to input features.
  3. Warp Image
    • provides interactive functionality to establish the control points.
    • When control points have been established, the distance between the transformed point and real position for that point (RMS residual error) is calculated.
  4. Resampling
    a process that fills each pixel of the new image derived from an image-to-map transformation with a value or a derived value from the original image.
  5. Pyramiding
    • Reduced resolution dataset (RRD files)
    • Technique commonly used for displaying large raster data sets. 
    • Builds different pyramid levels to represent reduced or lower resolutions of a large raster. 
    • When viewing entire raster, we view it at the highest pyramid level; as we zoom in, we view more detailed data at a finer resolution.
  6. 3 Main Causes of Location Errors
    • Human errors – hundreds of features need to be traced; it is reasonable that errors will be made
    • Scanning and Tracing errors – duplicate lines, collapsed lines, misshapen lines
    • Errors in spatial location of control points
  7. Measurement Scales
    • Nominal: Categorical, green, blue, male, female, elm, oak, Democrat, Republican, soil types 
    • Ordinal: ordered data - small, medium, large; first, second, third
    • Interval: arbitrary 0; equal intervals between values; 10 degrees, 20 degrees
    • Ratio: definite 0 point; age, height, length time
  8. Types of Database Design
    • flat file
    • hierarchical
    • network
    • relational
  9. Normalization
    • Process of decomposition of flat files or data
    • Attribute data is broken down to small tables
    • Still maintains necessary linkages between them.
  10. Ways to Classify Data
    Variety of different classification methods:

    • Jenks Natural Breaks
    • Equal Interval
    • Defined Interval
    • Quantile
    • Standard DeviationManual (set your own)

    Same data may appear differently
  11. Jenks Natural Breaks
    • Exploits natural gaps in data
    • Breaks that best group similar values and maximize the differences between classes. 
    • Features are divided into classes with boundaries set where big jumps in the data values exit. 
    • Good for unevenly distributed data.
  12. Equal Interval
    • Divides range of values into equal-sized subranges, (i.e. 0–100, 101–200, and 201–300). 
    • Emphasizes amount of an attribute value relative to other values.
    • Best applied to familiar data ranges, such as percentages and temperature.
  13. Defined Interval
    • User chooses class size. 
    • Specifies the interval value. 
    • Data determines number of classes based on the interval.
  14. Quantiles
    • Each class contains equal number of features. 
    • Well suited to linearly distributed data. 
    • Since features are grouped by number in each class, map can be misleading with unevenly spaced class ranges.
    • Similar features can be placed in adjacent classes, or features with widely different values can be put in the same class.
    • Minimize this distortion by increasing number of classes.
  15. Standard Deviation
    • Shows how much a feature's attribute value varies from the mean. 
    • ArcMap calculates the mean values and the standard deviations from the mean. 
    • Class breaks are then created using these values. 
    • A two-color ramp helps emphasize values above (shown in blue) and below (shown in red) the mean.
  16. 3 Labeling Options
    • Dynamic
    • Simple
    • Annotation
  17. Dynamic
    placed automatically for an entire layer and behave as a group

    • Turn on/off for entire layers
    • Redrawn each time the map view changes
    • Uses Autoplacement to ensure no overlaps between labels
    • Unavoidable overlaps are discarded
    • Can specify classes with own symbols
    • Can specify placement priorities
    • May change between screen and printing
  18. Simple
    Placed by user individually using text boxes from the DRAW tool bar.
  19. Annotation
    • Created from dynamic labels
    • Stored permanently with feature class
    • Provides significant control over independent labels and their positions.

    Can be stored three ways:

    • As text in the map document
    • As a feature class in a geodatabase
    • As feature-linked annotation in a geodatabase:

    • If the feature gets deleted, so does the label
    • Cannot go back to dynamic labels

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