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19 Cards in this Set
- Front
- Back
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GIS involves both spatial and attribute data, what is the difference between spatial and attribute data ?
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Spatial data relates to the geometry of spatial features and attribute data describes the characteristics of spatial features.
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What is the difference between the Vector Data model and the Raster Data model ?
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The characteristics of points, lines, and polygons make up the Vector Data Model and the Raster Data Model deals with pixels.
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What are the four levels of measurement ?
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Nominal, Ordinal, Interval, and Ratio.
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What are the characteristics of the Nominal level of measurement ?
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-Simplest form of measurement
-Observations are placed into two or more exclusive categories - Coding simply states if the values are the same or different. Ex. Ecozones of Canada/Landuse (String/Integer) |
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What are the characteristics of the Ordinal level of measurement ?
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-Objects are places in some rank order (1,2,3/High, Medium, Low)
-Order is meaningful but magnitude between objects is not meaningful. Ex. Average age of death by census tract (integer) |
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What are the characteristics of the Interval level of measurement ?
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-Objects are ordered and the magnitude between them is meaningful.
-How much more or less the attribute being measured is possessed by one object or another (Real Number) |
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What are the characteristics of the Ratio level of measurement ?
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-Objects are ordered and the magnitude between them is meaningful
-How many times one object varies from another on a particular attribute. Ex. 2010 Hamilton Municipal Election percentage votes for Bob Bratania (Real Number) |
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What are some table sources in Arc Gis ?
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dBASE files, INFO files, Excel Spreadsheets, Microsoft Access
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What are the two types of attribute tables ?
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Feature Attribute Table, and Stand Alone Table
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What are the characteristics of a Feature Attribute Table
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-Stores the attributes of a map
-Associated with a spatial data layer -Has fields for spatial information |
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What are the characteristics of a Stand Alone Table ?
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-Stores any tabular data
-Not associated with spatial dat -OID instead of FID |
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What are the three field properties of a table ?
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-Length - The total characters a field can store
-Precision - The total widths of digits a numerical field can store -Scale - The number of decimal places |
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What is a database and which type do GIS vendors use ?
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-A database is a collection of interrelated tables in digital format and the Relational Model the most widely used database in the computer industry was created by IBM's San Jose Research Lab in the early 1970s
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What are the characteristics of the Relational Model ?
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-Each column or field represents an attribute
-Each row of attribute values represents an object and is called a tuple -A table is called a relations and is made up of a set of tuples and each relation occurs once. |
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How are tables connected in the Relational Model ?
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-Tables are connected by keys known as:
-Primary Key: is one or more attributes whose values uniquely identify a tuple -Foreign Key: is one or more attributes in a relation, which identify the primary key in another relation -Linking mechanism is referred to as a relational join |
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What are the three types of connections available to link tables ?
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-One-To-One: One tuple in Table A is related to one tuple in Table B and vice versa
-One-To-Many: a tuple in Table A can be related to many tuples in Table B, but a tuple in Table B is related to only one tuple in Table A -Many-To-Many: a tuple in Table A can be related to many tuples in Table B and a tuple in Table B can be related to many tuples in Table A |
