Data in GIS Flashcards
xtichs
Attribute data
Data that describes the characteristics of spatial features and can be quantitative/qualitative.
also known as Non-spatial data
The 1 data types in GIS
Spatial
Attribute/non-spatial
What is data modelling
The process of defining and organizing data from real world into consistent digital data set that is useful and reveals information.
State the four levels of abstruction/generalization
Reality
Conceptual
Logical
Physical model
The 2 types of geometric data data models
Raster model
Vector model
Data models in GIS
Vector data model
Raster data model
Triangulated Irregular Network data model
How does the cell size affect Raster data
Level of detail/spatial resolution spatial data is often dependent on the cell (pixel) size
The smaller the cell size the higher the resolution.
Compare small and large cell sizes in raster data
SMALL;
Higher resolution
Higher feature spatial accuracy
Slower display
Slower processing
Large file size
LARGE;
Lower resolution
Lower feature spatial accuracy
Faster display
Faster processing
Smaller file size
Advantages of raster data model
Simple data structure
Can rep continous surfaces & perform surface analysis.
Can uniformly store points, lines, polygons & surfaces.
Can perform fast overlays with complex data structures.
Raster data model can represent the following data
Visual images
Discrete values
Continous values
Null values
Disadvantages of radter data
Spatial inaccuracies ( limits imposed by raster dataset cell dimension).
Very large daya sets
Loss of precision ( restructuring data to regularly spaced raster cell boundary)
Advantages of vector data model
Less disk storage space required.
Efficient for topological relationships graphical output more costly resembles hand drown maps
Easy to edit
accurate map
output efficient
projection transformation
Disadvantages of vector data model
complex data structure
Less compatibility with remote sensed data
expensive software and hardware
not appropriate to represent continuous data
overlaying multiple vector are often time consuming
What is the vector approach to handling a digital elevation
Triangulated irregular network
What are the advantages of triangulated Regular network data model
Ability to view 2.5d and 3D
Users can describe a surface at different levels of resolution based on the points that were collected
TIN interpolation gives GIS uses greater analytical capabilities
Provide simplified model that represents collected data points
