GIS Section 3 Flashcards
Studying for GIS Midterm!
What are the components of spatial data?
- spatial objects
- attributes
- topology
- graphic primitives
What is a data model?
set of guidelines for the representation of the organization of data in a database
can be SPATIAL or NON-SPATIAL
What data models are there for spatial data?
- vector
- raster
What are the 4 non-spatial data models?
- hierarchical
- network
- relational
- object-oriented
How is GPS transferred to a GIS?
- text files
- CSVs
- GPX files - used by many devices, represents either waypoints or tracks
How are air photographs georeferenced?
- well-distributed Ground Control Points (GCPs)
- coordinates processed by least squares regression
- correct distortions with the proper transformation equations
Why are air photos always distorted, and how can we minimize the distortion?
Since air photos are photos, the image at the edge comes into the camera from a greater angle than the image center, creating distortion
can be fixed with:
- several clearly discernible Ground Control Points
- the proper Transformation Equations
What are the elements of the vector data model?
- vectors of coordinate pairs
- topology
- attributes
What is the essence of the vector data model?
The abstraction of real-world objects into graphic primitives
What are the 2 approaches to storing vector data?
- polygon storage approach - stores polygons as units
- arc storage approach - stores arcs as complete units
What is the problem with the polygon storage approach in vector data?
Shared boundaries between polygons!
In arc topology, what is the ‘polygon’ outside of your polygons?
U for Universe!
What connects a feature with its attributes in the attribute table?
Feature Identifier - FID
- ie. a unique name for each feature
