GEOG 281 Flashcards
What is GIS?
Geographic Information Systems - a method that utilizes specialized software to analyze spatial data
What is the difference between GIS and the fields of cartography, remote sensing, and photogrammetry?
cartography - the science and art of map-making
remote sensing - the science of earth observation from space
photogrammetry - the science of measurement from photographs and images
It is tempting to think of GIS as a computer containing maps. Explain why this vision is limiting.
GIS does so much more, data integration, dynamic analysis, decision support, interactivity, complex queries, and goes into so much more depth than typical maps
What are the limitations of using GIS?
Data quality and availability, cost, technical complexity, scalability issues, user bias, spatial resolution limitations, software compatibility, and legal and ethical considerations
why is a well prepared data model vital for a successful GIS analysis?
Ensures that data is well organized, integrated, and aligned with analytical objectives, enabling accurate insights and effective decision-making
Raster and vector data models - which represents the real world most accurately?
Vector, it captures precise shapes and boundaries, and is more accurate for discrete features
what would happen to a polygon when changing the output resolution of a raster image?
loss of detail, pixelation, aggregation or fragmentation, and data loss
What are the implications of vector data models?
precision and accuracy, attribute data, and topology
What are the implications of raster data models?
continuous data representation, resolution and detail, and ease of analysis for spatial patterns
When would you prefer a raster data model?
Continuous phenomena (elevation and temperature), showing variations smoothly across space
How would you describe the shape of the earth?
Oblate sphere, slightly flattened at the poles and bulging at the equator due to its rotation
How is a geoid different from an ellipsoid?
Geoid - irregular surface that represents sea level and variations in Earth’s gravitational field
Ellipsoid - smooth, mathematically defined shape that approximates earth’s size and shape
What is the difference between a global and local/regional datum?
global datum - provides uniform reference framework for the entire earth
local/regional datum - tailored to a specific area, often higher accuracy by fitting the geoid/ellipsoid to the local area
What problems can arise when overlaying two GIS layers that are defined with different datums?
misalignment and distortion, leads to inaccuracies in spatial analysis and interpretation of geographic features
What is a map projection?
A system in which locations on the curved surface of the earth are displayed on a flat sheet or surface according to some set of rules
How can map projection distortion be assessed and visualized?
Tissots indicatrix (the circles showing distortion)
What are the three properties that can be preserved in a map projection?
shape (conformity), area (equivalence), and distance (equidistance)
What are three physical classes of map projections?
cylindrical (mercator), conic (albers equal-area), and planar (azimuthal) (lambert azimuthal equal-area)
Explain the difference between a data model and database model.
data model - defines structure, relationships, and constraints of data within specific application context
database model - overall design and organization of data within a database management system, including how data is stored, accessed, and manipulated
How do we build topography after digitizing a map? How does this differ from the spaghetti vector model?
by creating a structured representation of the terrain using techniques like triangulated irregular networks (TIN) or digital elevation models (DEMs), which organizes data into network of connected points or grid cells, but spaghetti vector model represents features as unstructured lines and polygons without inherent spatial relationships
How does the organization of this hierarchical data files differ from the organization of relational data files?
hierarchical - organized in tree-like structure with parent-child relationships
relational - organized in tables that can establish many-to-many relationships through the use of keys, allowing for more flexible querying and data manipulation
Why is a relational database model well-suited for GIS?
efficiently manages complex spatial data relationships, allows for easy querying and analysis through its tables, and supports integration of diverse datasets
How do spatial queries differ from SQL queries?
spatial queries - consider geometric relationships and properties of spatial data (proximity or intersection)
SQL queries - focus on non-spatial data retrieval and manipulation based on attribute conditions with structured tables
What are spurious polygons and what characteristics of data cause them?
they are misleading polygon features that come from inaccuracies in spatial data, they are caused by overlapping geometrics, poor digitization practices, or insufficiently defined boundaries
What are the three types of typological overlap?
spatial overlap, attribute overlap, and topological overlap
what is spatial overlap?
two or more geographic features occupy the same physical space, such as overlapping polygons
what is attribute overlap?
happens when different features share similar or identical attribute values, leading to potential confusion in classification or analysis
what is topological overlap?
involves the relationships between features, such as when boundaries intersect or share points, which can complicate spatial analyses and data integrity
describe an application where you would use proximity analysis. What kind of operations would you use?
can be used in urban planning to determine the best locations for new amenities, they would used buffer analysis, nearest neighbor analysis, and spatial joins
