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Published byJanice Sims Modified over 9 years ago
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Demonstration...... How to create meaningful Maps - using graduated symbols - using graduated colours - using Classification methods Analyzing techniques..... Attribute Query Location Query
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Display features with one colour Best for Nominal data Eg: Name, type, Condition, category Best to display Classes
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Further details about Quantities..... 1. Graduated colour Series of symbols whose colour change according to the value of attribute Eg: Temperature maps – Colour ranging from blue to yellow Most useful for showing data that is - Ranked : 1 to 10 or low to high 2. Graduated Symbol Similar to graduated colour, except variation is in the size of point or line Most useful for showing data that is - Rank or progression : Business rank according to the sales 3. Dot density map Symbolize polygon features using dots inside the polygon to represent an attribute Each dot is a specific value eg: In a population map, each dot might represent 100 people.
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Classification Methods....... For graduate colour or Symbol 1. Natural breaks Default method Identifies break points by looking for groupings and inherent in the data 2. Quantile Each class assigned the same number of features eg: lowest 5 in one class and next 5 in the next class Best for the data that are linearly distributed 3. Equal Area Classifying polygon features by finding break points in the values - may have low, medium and high class, but have different number of values Total areas of polygons in each class almost same (Weight in the classification equal to its area) 4. Equal Interval Divided range of values into equal sized sub ranges eg: class value range (113) Low = 12-125, medium = 126-238 High = 239 – 351 best for to show known percentages
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Analyzing Geographic Data In a GIS, a query is a question about features. There are two types of queries: What is a Query...... 1,. Attribute Query - looking for features that have specific attribute values Eg: How many Petro Canada Gas Stations are located in Toronto ?
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Suppose you want to know how many aerodrome (helicopter) are Located In GTA area. You could use Aerodrome layer to find the answer.
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To find out the helicopter lands, you would construct following Query expression: Attribute value Operator Attribute Filed
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The result is a set of selected features that have attribute value you are interested in
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Suppose you want to know how many helicopter land are located in city of Brampton.... Using Aerodrome Type and City attributes, you could construct The following expression Attribute Field1 Operator Attribute Field2 Attribute values Two aerodromes have been selected Connector
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2. Location Query
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See Questions below......
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Suppose you want to select health care facilities within 200m of the schools..........
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Location query could be phrased like this..... “Which feature in Health Care facilities layer are within a distance of 200m of school layer “ Features in a Layer to be selected Location relationship (Base) Relate Location layer Distance
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Final results.... Number of selected features
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Create new selected feature layer............
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