GEOG215 Flashcards
GIS
Geographic Information System. System for capturing, storing, manipulating, and displaying data that is systematically related to the Earth.
What ways can GIS be used?
We can investigate patterns within a location, geographic relationships, model what-if scenarios, and store large data sets.
What are the stages of a GIS project?
Data Input (GPS collection, UAV) –> Data Storage –> Data Manipulation (align with coordinate system) –> Data Analysis (slope) –> Data Output (3D model).
What do spatial professionals do?
Capture, analysis, modelling, design, and visualization of geographic data to deliver insights and understanding.
What is GI Science?
Science behind the technology. A scientific approach to the fundamental issues arising from the use of GIS and related technologies
What is geographic information?
Any information that refers to a location on the Earth’s surface. So, = spatial data.
What is spatial data?
Spatial data is data that has both:
- Description
- Spatial component (geometry)
Eg, where the city is located and what it is beside.
Data Model
A spatial database is a realisation of a data model.
- Real world view
- Map/screen view (simplification of real world to give spatial component)
What are layers?
The visual representation of an individual geographic dataset in any digital map environment. Works similar to a legend item on a paper map within the same location.
Why do we need layers?
To represent real world data of the same location without complicating display/storage.
Why is representing things in layers so useful?
Layers can be turned on and off, allowing for the representation of specific data alone or in conjunction.
What are the two types of spatial data?
Vector and Raster
Spatial Data: Vector
Spatial or coordinate data represents features that have a known location on the earth. Comprises:
- Points (X and Y locations)
- Line (Connected X and Y locations)
- Polygon (Connected X and Y locations that contain information in a enclosed area).
Vector: Points
X and Y locations
Vector: Lines
Connected X and Y locations
Vector: Polygon
Connected X and Y locations that contain information in a enclosed area
Spatial Data: Raster
Row and column matrix which represents geographic space. Includes aerial imagery.
Raster cannot identify that the cell next to it contains information that is similar or different - making it harder when representing roads, wetlands, etc.
Geometric Representation of Spatial Feature
Uses geometries of point, polyline, and polygon to represent vector-base spatial features.
Points = 1 or more point.
Polyline = set of line segments (one or more lines, connected or unconnected).
Polygon = 1 or more areas.
Vector vs Raster Data
Vector: object based - it’s all about the spatial features. Each feature is coded uniquely, which allows overlap - raster data cannot.
Raster: Geographical features are represented by values in matrix (or mesh/lattice grid/array). Elevation is a surface, where each cell has a value.
Attribute Data
Information linked to the geographic features (spatial data) that describe features. They are the “non-graphic information associated with a point, line, or area elements in a GIS.”
Vector data offers much more attribute data, while raster is much less detailed.
What 3D models have been used to approximate the Earth’s surface?
Ellipsoid, geoid, spheroid.
Why can’t we use a sphere for coordinate systems?
Earth bulges at the equator, doesn’t account for topography.
What are geographic coordinates measured in?
Lat and long, degrees, minutes, seconds.
What is a meridian?
Lines of equal longitude, beginning in Greenwich. Measures 180, East to West.