Lecture06

# Lecture06 - Why Is It There? Getting Started with...

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1 Why Is It There? Why Is It There? Getting Started with Geographic Information Systems Chapter 6 6 Why Is It There? 6 Why Is It There? z 6.1 Describing Attributes z 6.2 Statistical Analysis z 6.3 Spatial Description z 6.4 Spatial Analysis z 6.5 Searching for Spatial Relationships z 6.6 GIS and Spatial Analysis Dueker Dueker (1979) (1979) z “a geographic information system is a special case of information systems where the database consists of observations on spatially distributed features, activities or events, which are definable in space as points, lines, or areas. A geographic information system manipulates data about these points, lines, and areas to retrieve data for ad hoc queries and analyses ". GIS is capable of data analysis analysis z Attribute Data – Describe with statistics – Analyze with hypothesis testing z Spatial Data – Describe with maps – Analyze with spatial analysis

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2 Describing one attribute Describing one attribute Flat File Database Record Value Value Value Attribute Attribute Attribute Record Value Value Value Record Value Value Value Attribute Description Attribute Description z The extremes of an attribute are the highest and lowest values, and the range range is the difference between them in the units of the attribute. z A histogram is a two-dimensional plot of attribute values grouped by magnitude and the frequency of records in that group, shown as a variable-length bar. z For a large number of records with random errors in their measurement, the histogram resembles a bell curve bell curve and is symmetrical about the mean . If the records are: If the records are: z Text – Semantics of text e.g. “Hampton” – word frequency e.g. “Creek”, “Kill” – address matching z Example: Display all places called “State Street” If the records are: If the records are: z Classes – histogram by class – numbers in class – contiguity description, e.g. average neighbor (roads, commercial)
3 Describing a classed raster grid Describing a classed raster grid 5 10 15 20 P (blue) = 19/48 If the records are: If the records are: z Numbers – statistical description – min, max, range – variance – standard deviation Measurement Measurement z One: all I have! [6:00pm] z Two: do they agree? [6:00pm;6:04pm] z Three: level of agreement [6:00pm;6:04pm;7:23pm] z Many: average all, average without extremes z Precision: 6:00pm. “About six o’clock” Statistical description Statistical description z Range : min, max, max-min z Central tendency : mode, median (odd, even), mean z Variation : variance, standard deviation

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4 Statistical description Statistical description z Range : outliers z mode, median, mean z Variation : variance, standard deviation Elevation (book example) Elevation (book example) GPS Example Data: Elevation Mean Mean z Statistical average z Sum of the values for one attribute divided by the number of records X i i1 = n = X / n
5 Computing the Mean Computing the Mean

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## This note was uploaded on 12/28/2011 for the course GEOG 176a taught by Professor Clarke during the Fall '09 term at UCSB.

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Lecture06 - Why Is It There? Getting Started with...

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