Geographic Information Systems

Chapter 1.

· GIS composed up of computer models and tools to analyzing maps

· the maps contain layers- a collection of geographic objects that are alike

· each object in a layer is called a feature

· surface- is a single continuous expanse that changes from one location to another according to the depth

3 Geometric forms (collectively called vector data)

· polygon- represents large things

· line – represent things to narrow to be a polygon

· point-represents things to small to be a polygon

· raster- a matrix of identically sized squared cells that represent a unit of surface area

· features have location a grid (coordinate system used to put features in there proper places on a map

· scale- expressed ratio relationship between the size of features on a map and the size of the corresponding places

· information about a feature in a layer is stored in a table and each category of information called attributes

· thematic maps are maps in which colors or symbols are applied to features to indicate their attributes

· areas of overlay a new feature is created when the right features are in place within a boundary

Chapter 2.

ArcGIS Desktop (software product line)

· ArcReader-lets you view and print digital maps

· ArcView- makes the maps and data allows for query data, analyze spatial relationships and overlays

· ArcEditor- additional data and editing tools

· ArcInfo- spatial analysis tools

GIS

· ArcMap- application for map making and analyzing data

· ArcCatalog- the data management application

ArcGIS extensions

· ArcGIS Spatial Analyst- divides geographic space into a matrix and allows for stat summarize

· ArcGIS 3D- ability to see spatial data in three dimension

· ArcGIS Geostatistical Analyst- allows for evaluation of measured spatial data according to statistical principles

ArcGIS System

· Mobile GIS

· Server GIS

· ArcSDE

· Embedded GIS

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Chapter 5

• Map used to determine what is inside an area and to monitor what’s occurring inside it
• Depending on data and the number of areas or features you have depend on how you go about it

Single area- lets you monitor activity or summarize information about an area

Multiple areas- lets you compare areas by it being contiguous, disjunct or nested

If you have a list or count of features need to include those that are partially within the boundary

How to find out what’s inside

• Drawing the areas and features (visual approach)
• Selecting features inside the area (subset of features of a layer get summary of features)
• Overlaying the areas and features ( combines features and attributes inside what areas)

The Results

• Counts (total # of features in an area)
• Frequencies ( the number of features within a given value)
• Summary of numerical attributes ( sum, avg., median, standard dev.)

Vector method- splits category or classes where they cross areas and creates a dataset with the areas that result (more precise measures)

Raster method- compares each cell on the area layer to the corresponding cell on the layer containing the categories it counts the number of cells of each category within each area and calculates the areal extent by multiplying the number of cells by the area of a cell and gives a table (more efficient but can be less accurate)

Chapter 6

How to map what’s near by

• Map gallery
• Traveling
• Set by distance
• Summary statistics
• Total amounts
• Amount by category

Methods of how to get what’s near by

• Straight line method
• Distance or cost over a network
• Cost over a surface

Setting travel parameters

• Using distance
• Using cost
• Turns and stops

Chapter 7

• Maps help map changes and help anticipate future conditions decide on course of action or evaluate the results of an action or policy by mapping conditions before and after an action or event
• Maps can show change by location and condition of features at each date or calculate the difference

Types of changes

• Change in location
• Change in character or magnitude
• Features that move (discrete or event)

To evaluate need to know how much of a change and how fast the change

Change shown by

• Time series
• Tracking map
• Measuring and mapping change

You can map change by showing the location and conditions of features of each date.  You can also map the difference in a value between two and more dates.

·         Knowing the type of change and type of features you are working with, it will help you decide how to map the change.

There are 3 types of time patterns:

     A trend: change between two or more dates at a time.

  Before and after: conditions of something before an event, and after the event

A cycle: change over a period time; day, month, year.

Chapter 2 Mapping relationship and points

• By looking at the location of features you can begin to explore causes for the patterns you see
• Maps should be appropriate for the audience and the issue being addressed
• Choice of map and presentation of map affects the amount of information you’ll show
• Maps can show where features are and can reveal patterns
• Subsets reveal patterns that aren’t apparent when mapping all features   
• Features by type separate categories can make patterns within a category and across categories and the relationship

 Creating a Map

• Assigning geographic coordinates- each location needs a point
• Category values-each feature given an identification type and provide an understanding of how a place functions
  • have no more than 6-7 categories
  • fewer categories makes for easy understanding but reduces the amount of detail

            Group categories 

Assign each record 2 codes one for detailed category and one foe its general category

• Create a table containing one record for each detailed code with its corresponding general code
• Assign a symbol to the various detailed categories that makes a general category  

• Map scales- the smaller the area mapped the easier the individual features can be to distinguish,
  • by zooming in or our you may see patterns that were not evident before    
• Choosing color and symbol-  linear features use different widths or symbols that implied ranking the category,
  • roster layers display similar categories in different shades of the same color can make overall patterns clearer but difficult to distinguish ,
  • text labels can help distinguish categories
• Mapping reference features – bring more meaning to the map by only referencing features specific to the analysis   

 Chapter 3

Map of most and least- to find places that meet their criteria and take action, and see the relationship between places and based on a quantity associated with each

Mapping based on quantities adds an additional level of information beyond simply mapping the locations of features

Mapping patterns- see similar values help with figuring out the purpose of the map

 Types of features mapped

Individual locations- linear features or areas usually represented by graduated symbols and areas in shades

Allows for accurate picture of the data since no groups the features together

Real raw data

Help decide how to group the values into classes   

Data summarized- by area shading summarized based on value or charts

• When exploring data to see what patterns and relationships you can find are often in more detail and displayed in various ways by exploring the data to see what emerge and the questions that they bring
• When presenting map you will generalize the data to reveal the patterns
• Knowing the type of quantities being mapped help how to present the data by counts or amounts, ratios or ranks

Counts and amounts- show the total and actual #

• Lets you see the value of each feature as well as the magnitude compared to other features

Ratios- show the relationship between two quantities and allows to even out the differences between large and small areas and the proportion show what part of a whole each quantity represents

Ranks- put features in order from high to low

• show the relative value rather than measured values used when direct measurements are difficult ranks relative to where the feature
• falls in order 

·        Then figure out how to represent them on a map there becomes a trade off  between presenting the data and  

      generalizing the values to see the patterns  

Classes

Group with similar features by assigning them the same symbol that meet a specific criteria

Should always state explicitly on the map what the classes represent

            Types of classes 

                                    Natural breaks- class breaks set where there is a jump in values

                                    that emphasizes the differences between the heights 

                                    values within a class are likely to be similar and values between  classes different (mapping  

                                    values  not evenly distributed)

                                    difficult to compare with other maps 

                                     Quantities- class contain equal number of features and sizes

·        Emphasizing the relative position of a feature among other features 

                                    Equal interval- difference between the high and low values is the                                                   

                                    same for each class emphasizes the location of the few block

·        groups with the very highest median income                  

·        good for continuous data                                  

                                    Standard deviation- classes based on how much their values vary                                                 

                                    from the median    

                                    Seeing a point in the view of above or below the average

                                    Watch out for outliers may just designate with a special symbol 

 How to show quantities on the map

• Graduated symbols
• Graduated color
• Charts
• Contours
• 3-D view   

• Rounding the min and max values make the legend to read without changing the patterns in the map 
• Keep the map simple and present only the information necessary to show patterns in the data

Relationship between human geographers and GIScholars and the development of technology and applications and to geography

Didn’t interact until the late 1980s

 Human geographers saw GIS

• Simply an automated form of cartography
• Equipped to manage information is inadequate in the realm of knowledge production, concerned with facts but incapable of meaningful analysis

 GIScholars response

• The technological structure of GIS is controlled by computer science and the development of GIS in geography has led to the realization that databases and spatial analysis are subject to uncertainty and can be inaccurate
• GIS is most useful precisely when it is guided by geographers and is used in conjunction with knowledge rather than a substitute for it

 Concerns from GIS development

• The technological design and logic have far-reaching and lasting effects
• Development is presided over by private sector firms and that software is designed to solve corporate problems rather than addressing social inequalities
• Inaccessible to most people in the world
• Represents only a very limited linear type of problem solving

 Maps

• are not neutral representation of territory but a representation of social relations GIS could be able to enhance understanding a d increased peoples control over their own and others lives (COLONIZATION)
• GIS represents but perpetrates certain relations of power

 Two philosophical axes Epistemology

• The methods that we use to study the world and the lens that they entail in the perspective that a researcher uses to interpret entities and phenomena
• The lens used to interpret the ontology(thing) has a profound effect on its interpretation

 Types of lenses

•  
  • Social constructivism
  • Positivism
    • observations precedes theory, observations must be repeatable and theories are constructed on the basis of those observations
    • Scientific methodology is particularly suited to limited data sets of the past but does allow scientists to collect small amounts of data and extend their limited observations to a wide range of phenomena    
  • Realism
    • refers to forms of representation like sculpture or paintings that refer to the real world through the use of imagery and implies
    • that the world and events are linked to structures that cant be clearly seen but they can be discerned by studying the relationships between particular events or the abstractions that identify
    •  explain causal structures for phenomena under very specific circumstances
    • It presumes that there are facts that are independent of the mind but can be discerned through study and observation and puts greater emphasis on circumscribed form of empiricism as it does not necessarily link causes to other data
    • Accounts for the spatial-temporal locations of entities by connecting them to specific situations

 Ontology

• Refers to what something really is its foundational essence
• Formally defines sets of objects in which all the potential relationships between the objects are also well defined 
• Ontologies exist separately of the methods that humans use to study them but they are interpreted through epistemology how one studies and understands the world contributes to the ontologies that are depicted after having been interpreted through an epistemological perspective     

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• Use these axes as a way to understand and mediate between the intellectual territories of GIS and human geography  
• Researchers use the tools of computer science to create the ontologies but the concepts of philosophy to refer to the spatial entities manufactured by different methods of encoding
• The way the data is structured inside the computer has a profound impact on how the entities appear in the screen and the results of analysis          
• Social influences on GIS can be seen in the technology and how such insight can be used to imagine a better GIS

Geography started as a loose collection of scientists and empiricists interested in the physical nature of the earths surface as well as the role of geography in constructing politics and shaping behavior

GIS is frequently concerned with prediction rather than explanation and that requires identification of structural and causal mechanisms     

Pragmatism is an approach to knowledge that incorporates changes as necessary to accommodate new evidence or difficulty is antifoundationalist that it regards knowledge builders as participants rather than observers and knowledge is instrumental but only as a tool for organizing the world   

 Data Models Field Model Vector

·        Is the most ubiquitous in GIS

·        Most resembles traditional maps

·        Constructed from points, lines and areas

 Raster

·        Divides world into sequences of identical discrete entities by imposing a regular grid

·        May have hundreds of attribute layers for one geographical area but each layer includes the same grid cells

·        Each cell contains a single value for each attribute

·        Conceptual simplicity and ease of implementation

·        Well suited to operations which determine travel time or direction and comparison of neighbor cells

Both assume

·        That every point on the map falls into one category or another empty space does not exist

·        Are considered field models they treat the coverage as a gigantic field that can be subdivided

·        Are layer models that themes or attributes which are registered to the same geographical area under consideration and can compare with each other to determine a new set of attributes

·        Concerned with what accounting for every point in the geographical space being portrayed and what is at a certain location

·        Ways of dividing up geographical space into discrete units

 Object model

• Each representation a single attribute
• Location becomes one of many attributes associated with a particular object (points, lines, areas or volumes with 3-D)
• Vector building blocks but different in imaging space
• Groups of like objects are organized into classes and have attributes that apply to that class
• Allow for empty space and overlapping objects
• Concerned with the object itself and location is a secondary characteristic
• Epitomize the idea of discrete  separate entities in a frictionless neutral space          

Advantages

·        More closely parallel human conceptualization than location based field models

·        Entities can be defined by function or progress rather than by name

Field and Object Model