Data Management: Attribute Data Flashcards
Lecture 8
What is Attribute data in a GIS?
- In a GIS, attribute data are stored in attribute tables in .dbf files
- An attribute table is organized by row and by column
- Each row represents a spatial feature
- Each column describes a characteristic
- Intersect of row & column = Value of particular characteristic
of a feature - A row is also called a record
- A column is also called a field
What are Attribute data types?
Refers to how to GIS stores the attribute data.
*Number
*text
*character
*dates
*blob - binary large objects.
What is measurement scale?
Categorical:
1. Nomial
2. Ordinal
Numeric:
3. Interval
4. Ratio
What is nominal?
No ranking used for naming
What is ordinal?
Ranking with no number [large>medium> small]
What is interval?
Have known numerical intervals but no absolute zero ie. there are negative numbers. (temp in farenheit or celcius)
What is ratio?
Same as interval but has an absolute zero. (temp in Kelvin or rainfall)
What is the measurement scale of attribute data types?
nominal > ordinal > interval > ratio
Increasing level of sophistication.
2 types of attribute data
spatial attribute table
non spatial attribute table
Feature attribute table
- FeatureID = feature’s geometry
- Default
- Geometry like shape, length..
- 1 Row represents 1 spatial feature
- Flat file (looks like an Excel spreadsheet)
non-spaital attribute table
- No direct link to feature’s geometry
- Can link to feature table
- Aim: Efficient storage of attributes
- Avoid duplication
- Dbase file (Access, SQL, Oracle)
What is DBMS [database management system]?
Software package that allows us to manage and manipulate a database.
What is a database?
A database is a collection of interrelated tables in digital format.
What is the primary objective of a database?
collect and maintain information as well as to relate facts and situations that were previously unconnected.
What are the 5 types of databases?
- Flat file
- Hierarchical
- Network
- Relational
- Object Orientated