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33 Cards in this Set
- Front
- Back
5 Primary Functions of Analysis
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Description
Explanation Prediction Prescription Assessment |
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Description - What does this phenomenon look like?
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Basic information (height, etc.)
Context (relationships: <,>,=) Relative Position (nearer/farther than, higher/lower than) |
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Explanation - Why does phenomenon occur as it does?
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Attempts to describe cause and affect relationships
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Prediction - What if...?
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Use "problem modeling" and "scenario testing" to predict how phenomenon will change due to changing circumstances
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Prescription - We should...
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Make recommendation based on evaluation of models and scenarios
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Assessment - How'd it go?
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Evaluate outcomes of recommendation
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Rothermel Fire Model
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Predicts rate of fire spread thru uniform fuel array in absence of wind and topography
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Inputs of Rethermel Fire Model
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Fuel loading, depth, surface to volume ratio, heat contentt, moisture and mineral content, extinction moisture content
Later: wind velocity, slope |
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Outputs
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Rate of spread, intensity
Later: heat per unit area, flame length, direction of max. spread |
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Residential Fire Hazard Assessment Model (RFHAM)
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Inputs: vegetation type, features, and distribution with respect to structure
AND structural materials and building design |
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Scale
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Scale = smallest area that can be drawn or recognized (cannot represent objects accurately; influences content)
Minimum mapping unit - level of geography at which the data was captured (only dominant species are mapped) |
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Scale in Digital Maps
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Zoom feature gives false sense that scale can be altered.
Scale at which map is displayed says nothing about positional accuracy or completeness of disp. features |
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How do we know accuracy?
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Thru support documents that give +/- %error
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Data Aging
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Maps are static and become more inaccurate over time
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Symbolizing Imprecision (Examples: Streams, Fault Lines)
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Showing permanent, seasonal, intermittent streams
Using solid, dashed, dotted w/ increasing uncertainty |
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What are the most inaccurate data sources? Causes?
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Records of legal property boundaries.
Due to migrating land marks (e.g. streams) |
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Edge Mapping
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Digital procedure to ensure that all features crossing adjacent map sheets have same edge locations, attribute descriptions, and feature classes
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Orthorectification
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Geometric correction such that the scale of the photograph is uniform, meaning that the photo can be considered equivalent to a map
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Typology of Data Quality Error
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Validity
Precision Accuracy Reliability |
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Validity - Defintion
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Degree of confidence between what is intended to be measured and what is actually being measured
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Positional Validity
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Line in the data must be perceived as a line in reality
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Attribute Validity
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An attribute may be referring to only part of a feature.
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Precision - Definition
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Fineness of measurement scale (i.e. # of Sig Figs)
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Positional Precision
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Det. by ground resolution in data capture (reduced in maps)
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Attribute Precision
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Measure of how much aggregation of an attribute has been carried out
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Accuracy - Definition
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Closeness of measurement or observations to true values
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Positional Accuracy
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Confidence that position of feature as depicted is true
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Attribute Accuracy
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Closeness of measured and classified thematic values to reality
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Reliability - Definition
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Consistency of measures from several replications
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Positional Reliability
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Repeat sampling renders same results as initial testing
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Attribute Reliability
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Repeat sampling renders same results as initial testing
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What are US govts standards for data quality?
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Spatial Data Transfer Standard (lineage or history of a spatial dataset, positional/attribute accuracy, logical consistency, completeness)
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Topological Relationship
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Relationship of one spatial element with respect to another
(A inside B, D connected to B, C Disjoint from B, G overlaps E) VS. proximal (A near/far from B) Directional (G north of C) |