Geographic Information Systems

I presented along with Kim and Madline

Ch. 4 Bringing It All Together

Key point

• that analysis depends on data and that analysis has its own logics, assumptions and rationalities
• GIS is distinguished from cartography by its ability to analyze data
• GIS is precisely in the capability to efficiently analyze large volumes of data
• Models are not the territory but a way of simplifying representation so that we can better interpret the viability if environments for specific applications

Analysis

• treated like a metaphoric black box because the process is hidden because it occurs at the software level and the user just has to trust the results
• Ex) Shape is the ratio between the length of the straight line between two end points and the length of the curved line as it meanders between two points

GIS used to query spatial data, analyze spatial relationships and characterize regions, model spatial change over time and space

Spatial analysis allows the user re-represent data so that information and new perspectives emerge

It is the combination of visualization and computer generated modeling that allows GIS to surpass the map in its ability to communicate information

Types of Analysis

Overlay analysis

• The most common GIS analysis function
• Has the ability to overlay to reveal areas common to two or more attributes
• More suited for raster data because little computational challenge because each layer is already lined up spatially but can be applied to vector
• A set theory of mathematical constructs created by Cantor
• Theory uses the areas or spatial entities that are the basis of GIS for formally express relationships between them

Buffers

• Use GIS to demarcate a zone around a spatial object which should be included in the analysis
• Is a way of extending overlay analysis to account for areas that are affected by spatial change as well as to designate protected zones

Polygon overlay

• More difficult process is a basic overlay functions into vector package
• Complicated because it entails calculating new geographies because it is calculated based on the overlap between areas

Reclassification

• Technique allows for reclassification and generation of new values for spatial areas without changing the definition of spatial units
• It uses layers like overlay with the same basic geography but does not result in new spatial definition based on attribute relationship
• Also used to simplify attribute data that contain too many values for users to understand

Multi-Criteria Evaluation

• Is a roster based modeling tool that allows for several attributes to be combined in order to derive a sustainability index for location of spatial entity by defining the problem and relevant criteria
• The criteria is then scored depending on its relevance to the spatial solution
• Can incorporate more than one point of view and still provide results because it includes both factors and constrains

While quantitative or structured inquiries are a big part of GIS, visuality and intuition are what differentiate GIS from the approach to geography in the past.

-the human eye is a powerful tool to detect pattern.. greatly aids in GIS analysis but points out the role of subjectivity in GIS

-since beginnings of GIS, there has been a divide between people using the computer to analyze spatial data and those using it to map data in graphical form

-those who map data in graphical form rely on the power of the visual to convey patterns and concepts… viewed as an advantage

-GIS allows researchers to work with many more variables

-GIS researchers use “intuition” to make sense of the visual displays of geographical data

-today, geographical visualization is emerging as a subspecialty focusing on how humans interpret visual imagery, algorithms for data manipulation, and patterns of human-computer interaction

GIS used in epidemiology

-research at Simon Fraser University to investigate role of exploratory data analysis (EDA) in controlling infectious disease

-developed EDA procedure to improve understanding of demographic factors related to Tuberculosis incidences in Vancouver region

-prevention of TB is more economical than treatment, logical to develop strategies to ID at-risk geographical areas and allocate resources for TB control accordingly

-analysis capabilities of GIS combined with visualization facilities to provide a means of implementing EDA in an epidemiology context

-Exploratory Data Analysis process consisted of following stages:

1-exploratory visualization using a GIS

2-statistical and numerical analysis of spatial patterns and trends

3-visualization and communication of results using a GIS

4-repetition of stage 2 if needed with different statistical and/or numerical methods

5-final results as tables and graphs, maps of disease clusters or scenarios of disease propagation

-Through the use of spatial analysis techniques to ID clusters and then displaying those patterns, researchers identified five major clusters of TB in the Vancouver area

-one shortcoming of the study was that data included missing values… in order to ensure consistency/integrity of the results, the study was forced to discard instances in which attributes were not included

-as a result, analysis linked to the spatiality of the data was limited, and some clusters may have been missed: these factors point to the need for continued cooperation btwn GIS professionals and medical epidemiologists in order to design data collection and standardization

-visualization of results also affected by data reduction and by privacy constraints… 800m offset for each data cluster was chosen to protect the privacy of the individuals

Data and analysis are closely linked; especially true for epidemiological and population health studies which are often constrained by availability of data, their quality, and constraints to their integration.

-population health study underway at Simon Fraser Univ. to integrate multiple factors (housing, income, crime rates, environmental pollution, green space) into an analysis of population health status in the Greater Vancouver Regional District (GVRD)

-needed to create integrated data base for GVRD combining census info with data sources from health regions, municipalities, real estate boards, etc

-found two major integration challenges: spatial boundary definition and scale definition

-spatial boundary definition is challenging because data from municipal, regional, and provincial policy makers are all associated with different geographic regions- common problem in working with vector data

-most immediate challenge in integrating diverse data sets to develop “big picture” view of health status is to link the multiple relevant data sets to a relevant spatial framework/multiple frameworks

-spatial framework must be flexible so that areas of analysis change shape and extent depending on questions asked

-one way to accomplish flexible spatial framework is to use raster grids

-decided to adopt approach in order to integrate multiple datasets and to better facilitate the “data speaking for themselves”

One of the most persistent problems in GIScience is the modifiable area unit problem (MAUP)… occurs when spatial units (ie postal codes) or enumeration areas are aggregated into larger units, or when a map is redrawn at the same scale using a different spatial division.

MAUP closely related to another problem that plagues spatial analysis: ecological fallacy, when flawed conclusions about individuals are inferred from characteristics of an area.

Current goal is to analyze the distribution of health status in the GVRD using a variety of indices and MCE… chiefly concerned with nonmedical determinants of health/community health.

-traditionally, neighborhoods with compromised health profiles have been identified using indices that are applied to fixed vector spatial frameworks like census tracts or postal codes

-neighborhoods of robust or very poor health rarely fit neatly into the administrative jurisdictions outlined by the polygon… thus raster data formats are a better basis for identifying self-organizing constellations of factors affecting community health

-Jarman 8 is one of better known indices developed to measure underprivilege… was developed in teh UK to ID underprivileged areas for purposes of health care planning

-however, neither Jarman or the MCE analysis can substitute entirely for local, on-the-ground knowledge.

Context and frames of reference contribute to the legitimacy of any system of representation. It is not all about the calculating technologies inherent in GIS. What and how social and natural phenomena are represented depends on the priorities and vision of a society and its governing structures.

chapter 5

GIS- about 30 years old and just now become widespread because it use to be cumbersome and couldn’t be applied to any thing further then creating reports

key need to know how to structure your analysis and which tools to use for a particular task

GIS analysis-  can find out why things are where they are and how things are related

Maps- used to clearly and accurately present the information from the data

 Most common uses of maps

mapping were things go

            mapping the most/least

            mapping density

            finding what’s inside

            finding what’s nearby

            mapping change

 Steps of GIS analysis 

Framing the question-figuring out what information you need be specific as possible about the question your trying to answer determine how to approach analysis, which method to use and how to present results

Understanding your data- determined by the type of data will determine the specific method used, you have to know what you got and what you need to get

Choose a method- decide which method to use based on your original question and how the results of the analysis will be used

 Process the data 

Look at results- results can be displayed as a map, table or chart based on what information used and how you group your values

The type of geographic features your working with affect all steps of the analysis process

 The types of features

Discrete- the actual location represented by a spot based on line location

Continuous- ex) water can be found or measured anywhere, blanket the entire area being mapped no gaps and can determine a value at any given location use interpolation using the points to assign values to areas between points

Summarized by area- represents the counts or densities of individual features within area boundaries the data value applies to the entire area but not to any specific location within it ex) demographic data

 Ways to represent geographic features

Vector model- each feature is in a row in a table and feature shapes arer defined by x,y,z locations in space features can be discrete areas defined by boards are represented when analyzing vector data analysis involves summarizing the attributes in the layer’s data table

usually use continuous categories or discrete features when combining with other layers 

Raster model- features are represented as a matrix of cells in continuous space each layer represents one attribute and analysis occurs by combining the layers to create new layers with new cell values the cell size is important because it will affect the results of the analysis and how the map looks using use discrete features, data summarized by area and continuous numeric values           

Map projections- translate the locations on the globe onto the flat surface of your map get distortion because shapes of features being displayed, measurements of area, distance, and direction

Coordinate system- specifies the units used to locate features in 2-D space and the origin point if those units

 Each graphic feature has attributes

Categories- are groups of similar things help organize data values represented using numeric codes or text

Ranks- puts features in order from high to low applied when direct measurements are difficult down side its relative to the order of value

Counts and Amounts- show the total number 

Ratios

Different applications

Normative- focus on design

Positive – advances of science (implies that science confirms theories by finding evidence to support it)

Operational- time scale required for smooth functioning

Tactical- medium tern decesions

Strategic- long term

Transactional- constantly being updated as new information arrives  

Geographic- refers to the earth’s surface and near-surface

Spatial- refers to any space, not limited to just the earth’s surface

Geospatial- implying a subset of spatially applied specifically to the earth’s surface and near surface

Information systems help us to manage what we know , by making it easy to organize and store access and retrieve, manipulate and synthesize and apply knowledge to the solution of problems

Information- is data serving some purpose of data given some degree of interpretation (exists independently 

Knowledge- information to which value has been added by interpretation based on a particular context, experience and purpose (entails a knower) and much more valuable when it is applied to how the world works then how it looks because it can be used to predict

            Codified- if it can be written down and transferred relatively easy to others

            Tacit- more slow to acquire and much more difficult to transfer

Evidence- half way between knowledge and information as a multiplicity of information from different sources related to specific problems and with a consistency that has been validated

Wisdom- used in the context of decisions made or advice given which is disinterested based on all the evidence and knowledge available

Idiographic- geography that focuses on the description of form and emphasizes the unique characteristics of places

Nomothetic- geography which seeks to discover general processes   

GIS is able to bridge the gap between science and practical problem solving and using the software captures and implements general scientific knowledge, while the database of GIS represents specific information and gives practical value to both, a tool for revealing what is otherwise invisible in geographic information

First GIS was the Canada Geographic Information System, designed in the mid 1960s as a computerized map measuring system

By late 1960s the US Bureau of the Census that resulted in the development at Harvard University’s laboratory for computer graphics and spatial analysis to develop a general purpose GIS  and taken off since the 1980s and the internet has increasingly integrate into many aspects of GIS use    

Objective- problem solving in any terms to minimize or maximize tangible or intangible measurments

5 Components of the GIS anatomy

Network-

Users hardware- device the user interacts with directly in carrying out GIS operations

Software- runs locally in the users machine

Database- digital representation of selected aspects of some specific area of the earths surface or near surface

GIScience- viewed as anchored by 3 concepts the individual, the computer, and society that allows for research dominated by the individual is dominated by cognitive science, with its concern for understanding of spatial concepts learning and reasoning about geographic data and interaction with the computer that helps to redefine, reshape and resolve pre-existing problems from using the knowledge that GISystems implement and exploit

GIStudies- the systematic study of society’s use of geographic information including its institutions, standards and procedures

GIS is used to improve many of our day-to-day working and living arrangements

Why GIS- wider ability, price, greater awareness that decision making has geographic dimension that help in solving real-world problems

GIS application goal to mapping, measurement, monitoring, modeling and management

 Environmental Justice

In the environment geography matters referring to the conditions that surround us every day including natural attributes such as air and water and how they change depending on where we are and what else is near by

EPA in the 1980s all people regardless of their race, age, job, income, or education enjoy the same degree of protection from environmental and health hazards

1994 1^st federal mandate that legislation sought to focus federal efforts on ensuring that poor and minority communities were not disproportionately burdened by environmental hazards and that these communities had more say in the legal processes that brought environmental hazards in the first place