GEOG 281

Question 1

What is GIS?

Answer 1

Geographic Information Systems - a method that utilizes specialized software to analyze spatial data

Question 2

What is the difference between GIS and the fields of cartography, remote sensing, and photogrammetry?

Answer 2

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

Question 3

It is tempting to think of GIS as a computer containing maps. Explain why this vision is limiting.

Answer 3

GIS does so much more, data integration, dynamic analysis, decision support, interactivity, complex queries, and goes into so much more depth than typical maps

Question 4

What are the limitations of using GIS?

Answer 4

Data quality and availability, cost, technical complexity, scalability issues, user bias, spatial resolution limitations, software compatibility, and legal and ethical considerations

Question 5

why is a well prepared data model vital for a successful GIS analysis?

Answer 5

Ensures that data is well organized, integrated, and aligned with analytical objectives, enabling accurate insights and effective decision-making

Question 6

Raster and vector data models - which represents the real world most accurately?

Answer 6

Vector, it captures precise shapes and boundaries, and is more accurate for discrete features

Question 7

what would happen to a polygon when changing the output resolution of a raster image?

Answer 7

loss of detail, pixelation, aggregation or fragmentation, and data loss

Question 8

What are the implications of vector data models?

Answer 8

precision and accuracy, attribute data, and topology

Question 9

What are the implications of raster data models?

Answer 9

continuous data representation, resolution and detail, and ease of analysis for spatial patterns

Question 10

When would you prefer a raster data model?

Answer 10

Continuous phenomena (elevation and temperature), showing variations smoothly across space

Question 11

How would you describe the shape of the earth?

Answer 11

Oblate sphere, slightly flattened at the poles and bulging at the equator due to its rotation

Question 12

How is a geoid different from an ellipsoid?

Answer 12

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

Question 13

What is the difference between a global and local/regional datum?

Answer 13

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

Question 14

What problems can arise when overlaying two GIS layers that are defined with different datums?

Answer 14

misalignment and distortion, leads to inaccuracies in spatial analysis and interpretation of geographic features

Question 15

What is a map projection?

Answer 15

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

Question 16

How can map projection distortion be assessed and visualized?

Answer 16

Tissots indicatrix (the circles showing distortion)

Question 17

What are the three properties that can be preserved in a map projection?

Answer 17

shape (conformity), area (equivalence), and distance (equidistance)

Question 18

What are three physical classes of map projections?

Answer 18

cylindrical (mercator), conic (albers equal-area), and planar (azimuthal) (lambert azimuthal equal-area)

Question 19

Explain the difference between a data model and database model.

Answer 19

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

Question 20

How do we build topography after digitizing a map? How does this differ from the spaghetti vector model?

Answer 20

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

Question 21

How does the organization of this hierarchical data files differ from the organization of relational data files?

Answer 21

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

Question 22

Why is a relational database model well-suited for GIS?

Answer 22

efficiently manages complex spatial data relationships, allows for easy querying and analysis through its tables, and supports integration of diverse datasets

Question 23

How do spatial queries differ from SQL queries?

Answer 23

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

Question 24

What are spurious polygons and what characteristics of data cause them?

Answer 24

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

Question 25

What are the three types of typological overlap?

Answer 25

spatial overlap, attribute overlap, and topological overlap

Question 26

what is spatial overlap?

Answer 26

two or more geographic features occupy the same physical space, such as overlapping polygons

Question 27

what is attribute overlap?

Answer 27

happens when different features share similar or identical attribute values, leading to potential confusion in classification or analysis

Question 28

what is topological overlap?

Answer 28

involves the relationships between features, such as when boundaries intersect or share points, which can complicate spatial analyses and data integrity

Question 29

describe an application where you would use proximity analysis. What kind of operations would you use?

Answer 29

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