Demonstration......
• How to create meaningful Maps
- using graduated symbols
- using graduated colours
- using Classification methods
Analyzing techniques.....
• Attribute Query
• Location Query
Display features with
one colour
Best for Nominaldata
Eg: Name, type,
Condition,category
Best to display
Classes
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.
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
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 ?
Suppose you want to know how many aerodrome (helicopter) are Located
In GTA area.
You could use Aerodrome layer to find the answer.
To find out the helicopter lands, you would construct following
Query expression:
Attribute value
Operator
Attribute Filed
The result is a set of selected features that
have attribute value you are interested in
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
2. Location Query
See Questions below......
Suppose you want to select health care facilities within 200m
of the schools..........
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
Final results....
Number of selected features
Create new selected feature layer............
