Lecture 1: Vector structure and DB theory
What does geographical data contain?
X and Y coordinates, Attribute data (info about the object)
Where is vector data stored?
A file or database
Name the characteristics of points
dimensionless, one pair of X Y coordinates, each point has unique ID value
What kind of file is a coordinate file?
.shp
Where is the attribute data stored?
.dbf
Name the characteristics of lines
have one dimension, consist of ordered coordinate pairs, each segment has start node and end node
What is the spagetthi model?
The simple model with the same coordinates in the beginning and ending
Name the characteristics of a shape file
simple structure, non-topological, stores geometric location and attribute information in seperate files
What are the difficulties with the simple polygon model?
Storage problems, neighbour searches complicated, island polygons are hard to handle
Name the advantages of topological polygon structure
Shared lines stored once, Island polygon is easier to find, Different tables for describing different aspects of the topology
Which 4 database systems are there?
File
Hierarchial
Network
Relational database
Which advantages does relational databases have?
New information can be added continuously
different accessibility options
How to solve redundancy
make many small tables, make relations when needed
How does a georelational model look like
Stores spatial data and attribute data seperately in shape format
How does a object based data model look like
Combines geometries and attributes in one system in a geodatabase
Which database handles topology?
Geodatabase
Where are the coordinates (geometry) stored?
.shp
Where are the attributes stores?
.dbf