GIS Midterm 1

Definition of GIS

a computer-based system to aid in the collection, maintenance, storage, analysis, output, and distribution of spatial information

What does a GIS allow us to do?

visualize combinations of spatial information

Data is

spatial

GIS recognizes

spatial aspects of data

GIS as a system

collect, store, process, analyze, visualize

GIS as a software

actual tools

GIS as a way of ‘doing’ or a science/way of knowing

concepts, principals, and methods

Three key characteristics

uses geographical data (spatial)

capable of conducting spatial analysis (synthesis)

computer based (not just maps)

hardware components

software components

data entry

editing

data management

analysis

output

GIS in organizations

all maps do what?

lie - they are made up of choices about what to have and not

what does it mean to ‘do’ GIS?

combines skill, knowlegde, and techinical capacity

what are the three ways of ‘doing’ GIS?

solve problems/answer questions

use compsci principles to design, build, and test tools

studying tools, methods, and theories (GIS science)

Notable use of spatial analysis before GIS

John Snow’s 1850’s cholera outbreak map of London

Early US stats mapping example

Slavery in the antebellum south

When did GIS emerge?

1960s

What were the early links to GIS?

Academy + military + civil gov

Early computing tech

SYMAP and Canada GIS

When was GIS made practical for users?

1980s

SYMAP

1965 Harvard

Allowed for the first time relatively cheap and easy automatic computer cartography

Canada GIS

1970 combined computer cartography with geographic database from Canada Land Survey

First true GIS

What was the first “true” GIS?

Canada GIS

What are the 4 perspectives of GIS?

Business

Government

Geography

Society

Business perspective

Develop software

For-profit data services

Consulting

Government perspective

Planning

Public reporting

Project management

Geography perspective

Cartography/location

Relevance

Ontological/epistemology concerns

Ontology

How must world be in order for us to understand it

Epistemology

What methods do we use to understand the world

Society perspective

Role of GIS

Privacy

Growth/spread of location-based services

Role of technological change

Intersections between GIS and other social theories

Maps are

Representations based on decisions that are scale dependent

Why maps?

Communicate complex info concisely

Key things to think about for maps

Intended audience

Information that needs to be communicated

Area of interest

Production limitations

Three levels of scale

Level of detail

Extent/scope

Cartographic scale

Level of detail

Resolution

Amount of information found in data/displayed

Extent or scope

Size of the scale

Large-scale

Large area covered

Large ratio

Lots of detail

Small-scale

Small area covered

Small ratio

Very little detail

Cartographic scale

Map’s representative fraction or ratio

What are the 4 types of maps?

Reference or feature

Choropleth

Dot density

Isopleth

Reference or feature map

Shows basic information

Symbols may or may not be true to scale

Choropleth maps

Quantitative information displayed as shades or colors filling in an area

Dot density map

Quantitative information shown as dots per area

Isopleth map

Contours that connect points of equal value (ex topo)

Reference/feature map

Choropleth map

Dot density map

Isopleth map

How should you decide symbols?

Map’s purpose and audience

Logical connections

Cultural relevance

Not detract or distract

What do points show

Discrete objects or locations

What do lines show

Linear objects or locations

What do area patterns show

Density or features that take up defined space

Elements of a map

Legends

North arrows

Scale bar or ratio

Graduated symbols legend

Area legend

Scale bar

North arrows

Representation involves selecting

What we want to represent

Level of detail

How to represent

What are the 4 types of representation?

Space/time

Image

Visualizations

Maps (cartographic)

Space and time

Imagery

Visualizations

Map representation

Title

Media edge

Neat line

Data pane

Legend

Scale bar

North arrow

Representation allows us to

Predict, model, and analyze

3 attributes of phenomena

Position

Attributes

Time

Position is represented

with symbols

Omitted

Fused

Exaggerated

Simplified

Displaced

Scale

Ratio of distance on map to earth

Distance measurements determine

Shape, size, etc

T/F: time is optional

True

T/F: Location is not necessary

False

Locations need to be

Unique

Easily shared

Georeference

Shared means of explaining location and position

3 components of georeferecne

Coordinate system

Map scale/spatial resolution

Projection

What do you need to georeference?

Provision for fine spatial resolution

Ability to measure distance

Allowance for other spatial analysis

Cartesian coordinate system

2D systems = plane coordinate systems

Cartesian coordinate systems

Latitude

X-axis

Longitude

Y-axis

What is the only true geographic coordinate system?

Latitude and longitude

What are the reference planes for lat/long?

Equator and prime meridian

Coordinate pairs

Pairs of lat and long

Do lines of latitude intersect?

No, they are parallels

Do longitude lines intersect?

Yes, they are meridians that intersect at the poles

What must not be forgotten in coordinate pairs?

Hemisphere

Where is the origin for coordinate pairs?

0 d N/S, 0 d E/W

Intersection of prime meridian and equator

Latitude is

Angular distance north or south of equator

Longitude is

Angular distance east or west of prime meridian

What do latitude and longitude from when combined

Graticule or reference grid