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GIS > GIS Section 1 > Flashcards

GIS Section 1 Flashcards

Studying for Intro to GIS Midterm!

1
Q

What is a GIS?

A

An information system applied to geographic data, 2 main definitions:

  1. use geographically-referenced data to carry out operations for spatial analysis
  2. system of hardware, software, and procedures to support input, storage, retrieval, and display of geogrpahically-referenced data
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2
Q

What is the main purpose of GIS?

A

support DECISION-MAKING related to spatially-distributed entities

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3
Q

What are some benefits of using GIS?

A
  • consistent framework for spatial analysis
  • can make connections between activities
  • allows accessing admin records via their geographic position
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4
Q

Name some disciplines that contribute to GIS

A

cartography, surveying, statistics, computer science, mathematics (geometry), civil engineering, agronomy, ecology

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5
Q

Aside from hardware/software, what else goes into a GIS?

A

approaches/methods for data analysis, people and their knowledge!

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6
Q

What is the starting point for a good GIS?

A

user needs analysis
(identify what questions the GIS will be answering!)

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7
Q

What are the 3 main hardware components of a GIS?

A
  • input module
  • CPU
  • output module
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8
Q

What is a subsystem?

A

collections of dedicated hardware and software for accomplishing the main tasks of GIS (input and queries)

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9
Q

What are the main modules in a GIS?

A
  • input module
  • storage/database module
  • display/reporting module
  • data processing/transformation module
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10
Q

What is a DBMS?

A

Database Management System
(central control of data management – both spatial and attribute data, as well as topological rules)

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11
Q

What does the Retrieval and Transformation subsystem do?

A

retrieval - connects to output/display data

transformation - for maintenance (update and edit) or data analysis

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12
Q

What does the display and output subsystem module do?

A

prepare data for output via Output Module

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13
Q

Through which 3 modes can we view the world?

A
  • spatial
  • temporal
  • thematic (theme whose spatial variability = observed/measured)

(in practice, fix one mode (time), vary a second (space), and observe the third (theme))

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14
Q

What is ASCII?

A

American Standard Code for Informatino Interchange

contains characters used as text in categorical attributes (names)

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15
Q

What are the 6 data types?

A
  • binary
  • byte
  • integer
  • real
  • date
    -ASCII

(also packed binary but whatever)

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16
Q

What is the range of integer and real data etc.?

A

Integer: -32768 to 32768
(65,536 possible values)

Real: real numbers to 7 decimal places (3.4*10^38)

Bytes: 0-255

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17
Q

How many bits to store integers and reals(floating point)?

A

Integers: 32 bits

Reals: 128 bits

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18
Q

What are the two elements of efficient file storage?

A

rapid access and rapid cross-referencing!

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19
Q

What are the 3 components of spatial data?

A
  • spatial objects
  • attributes
  • topology
20
Q

What is a graphic primitive?

A

used to digitally represent real objects

21
Q

What are the basic 1-dimensional object types?

A

point, node

22
Q

What are the 7 basic types of 1-dimensional objects?

A
  • line segment
  • string
  • arcs
  • ring (of strings)
  • ring (of arcs)
  • link (between two nodes)
  • directed link
23
Q

What are the 4 basic 2-dimensional object types?

A

simple polygon
- complex polygon
- interior area
- picture element

24
Q

In rasters, what is the relationship between resolution and cell dimension?

A

high resolution = low cell dimension (small pixels)

25
Q

In what sequence are raster files read?

A

from top left corner

26
Q

What is pixel resolution?

A

the minimum linear dimension of the smallest unit of geographic space for which data are recorded

27
Q

What types of resolution affect how a map is read?

A
  • printer resolution
  • monitor resolution
  • actual map/data resolution
28
Q

What are the steps in creating a raster image?

A
  1. decide on level of resolution
  2. overlay regular grid on source map
  3. code each cell with an appropriate value
  4. input values in a text (ASCII) file
29
Q

What are the three methods for creating a raster image?

A
  • cell-by-cell entry
  • import from digital image source
  • import from scanned devices (paper maps)
30
Q

What 3 shapes are real-world entities abstracted into?

A
  • points (nodes)
  • lines (arcs)
  • areas/polygons
31
Q

What is the unique name of a feature?

A

Primary Key

32
Q

How are vector data (points, lines, polygons) stored?

A

points: single X,Y coordinate pair
Lines: string of X,Y pairs
Polygons: Closed loop of X,Y pairs (first and last are the same)

33
Q

What are the 2 storage approaches for vector data?

A
  • polygon storage approach (problem of shared boundaries)
  • arc storage approach (topology instead of shared boundary)
34
Q

What is planar enforcement?

A

the set of coded rules that objects must follow to build topology correctly (ex. two 1-D objects must not cross)

35
Q

What is the relationship between digitizing and editing?

A

poor digitizing –> large need for editing

36
Q

What is topology?

A

branch of geometry that deals with properties of features that are unchanging and depend on context (important in defining spatial relationships between objects)

37
Q

What are feature classes?

A

Features with the same type of geometry – ie. any grouping of points, lines, or polygons

  • feature classes have attributes stored in tables
38
Q

What are shapefiles?

A

vector files for storing location/attribute data of points/lines/polygons

  • accompanied by 2 other files (3 total)
  • SHP (geometry), SHX (indexing of feature geometry), DBF (database file as attribute table)
39
Q

What is a GCM?

A

Global Climate Model/General Circulation Model

  • practical example of raster data
  • useful in projecting climate change
40
Q

What physical processes can a GCM represent?

A
  • motion
  • thermodynamic energy
  • water vapour mass continuity
41
Q

How do GCMs differ (from each other)?

A
  • different grid approaches
  • different numerical methods for solution
  • vertical discretization
42
Q

How does a GCM grid represent the Earth?

A

200x200km lateral and 10km vertical grid cells (ie. atmosphere divided into many 3-D cells)

43
Q

What GCMs will have higher/lower resolutions?

A

higher resolution = local/regional GCMs
lower resolution = global GCMs

44
Q

What resolution do typical Global Climate Models have?

A

grid of ~300km squares

45
Q
A

GIS (9 decks)

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