Chapter 1 - Introduction

Why Does GIS Matter? Everything that happens, happens somewhere…

Location is an issue in many of the problems that society must solve…

Some of these problems are routine, others are monumental in scope…

Examples of Geographic ProblemsHealth CareDelivery CompaniesTransportationForestryGovernmentand MANY more...

Geographic Problems

Bases for ClassificationLevel of geographic detail or ScaleIntent or Purpose

Practical Objectives (Minimize cost, etc.)Driven by human curiosity (Science)

Use the same tools…Time Scale

Operational (day-to-day)transactional databases

Tactical (medium term)Strategic (long term)

Why is geographic information special?

It is Multidimensional (at least two coordinates required--x, y)

It can be voluminous (some geodatabases = terabyte)

It must be projected onto a flat surface

It requires special methods for its analysis

It can be very time consuming to integrate various types

It can be complex and expensive to update

It can require large amounts of data retrieval for simple tasks

from just Data to elusive Wisdom

“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 to solutions…”

DATA = numbers, text, symbols INFORMATION = data serving some purpose--implies some degree of selection, organization, preparation, interpretationEVIDENCE = multiplicity of information from different sources, related to a specific problem with a validated consistencyKNOWLEDGE = information to which value has been added by interpretation based on a particular context (a book is read)WISDOM = used in the context of decisions made or advice given--based on all the evidence and knowledge available

Knowledge about how the world works vs. knowledge about how the world looks….

“How it works” knowledge is most valuable => prediction

The software of a GIS captures and implements general knowledge, while the database represents specific information

an example of general knowledge = classificationmore sophisticated forms = rule sets

Everybody has their own definition of GIS

a container of maps in digital forma computerized tool for solving geographic problemsa spatial decision support system

a mechanized inventory of geographically distributed features and facilitiesa tool for revealing what is otherwise invisible in geographic informationa tool for performing operations on geographic data that are too tedious or expensive or inaccurate if performed by hand

General publicdecision-makers, community groups, plannersmanagement scientists, operations researchersutility, transportation, and resource managers

scientists, investigators

resource managers, planners, cartographers

Brief History of GIS

1st GIS = Canada GIS, 1960s (map measuring system)U.S. Bureau of the Census - 1970 census of population1970s - USGS, DMA, etc. (map creation/editing)1970s - digital remote sensing satellites (LANDSAT), GPS1980’s = price of sufficiently powerful computers falls below critical

threshold, commercial software companies established1990s = digital data sets become widely available

(DCW, 1992)1993 = Xerox PARC center publishes first web-based

interactive maps1996 = Commercial Internet Map Servers introduced (MapQuest)2000+ = GIServices (location-based services, g-commerce)

“The Era of Exploitation”

Components of a GIS

Hardware

Software

Data

People (SAPs)

Procedures

Network

GIScience and others’ terms

Systematic study of the fundamental issues arising from the creation, handling, storage, and use of geographic information, as a well-defined class of information in general.

Other terms currently being used:geomaticsgeoinformaticsspatial information sciencesgeocomputationgeo-information engineering

These terms have different roots and emphasize different ways of thinking about problems.

Chapter 2 - Gallery of Applications

“One Day of Life with GIS…” GIS affects each of us, every day….

Why GIS is becoming so widespread...

Wider availability of GIS through the Internet

Reductions in the price of hardware and software

Greater awareness of the geographic dimension of decision-making, etc.

Easier to use interfaces

Better technology to support applications (data visualization, data management, linkage to other software).

Proliferation of geo-referenced digital data (GPS, VARs, etc.)

“Commercial off-the-shelf” (COTS) applications

Accumulated experience in the industry (making it work…)

Typical Goals of Scientific Applications

Rational, effective, and efficient allocation of resources

Monitoring and understanding observed spatial distributions

Understanding the difference that place makes…

Understanding processes in the natural and economic systems

Prescription of strategies for environmental conservation

The five “M’s” of GIS Applications

MappingMeasurementMonitoringModelingManagement

Lambert’s versionMapping, Monitoring, Management, Analysis, Planning

Local Government Applications

Of the tasks undertaken by local governments, 70 - 80% are geographically related.

GoalsImprove the quality of products, processes, and services Protect the health, safety, and welfare of citizens

Inventory Applications (roads, parcels, facilities, etc.)

Policy Analysis Applications (resource demand, potential capacity, etc.)

Management/Policy-making Applications (facility siting, routing, allocation, projections, etc.)

Business and Service Planning (Retail) Applications

Geodemographics is a shorthand term for composite indicators of consumer behavior that are available at a small-area level (e.g., census tracts, postal zone, etc.)

basis for market area analysisfastest growing application of GIS

Operationalday-to-day processing of routine transactions and inventory analysis (ex: stock management)

Tacticalallocation of resources to address specific (usually short-term) problems (ex: store sales promotions)

Strategicsupport for planning to achieve long-term goals

(ex: opening new stores)

Logistics and Transportation Applications

Deals with the movement of goods and people from one place to another, and the infrastructure that moves them…

Each application requires two parts:Static - fixed infrastructure (highways, railroads, etc.)Dynamic - the goods and people that are moving around

GPS provides the technology to track vehicles, etc.

Recently, applications include dynamically updated maps on the InternetMany applications involve optimization methodsThese applications have provided substantial savings over traditional manual methods...

Environmental Applications

Earliest applications of GIS were in the environmental fields

Competition between alternative uses of land has driven many

applications of GIS

Satellite remote sensing used to monitor land use change

Dynamic simulation models

Links to non-spatial models

Professional standard in most fields today...

Chapter 3 - Representing Geography

Representations or Modelshelp us assemble far more knowledge about the Earth than is possible on our own.Are reinforced by the rules and laws that we have learned to apply to the unobserved world…

Toblers’ First Law of Geography: Everything is related to everything else, but near things are more related than those far apart.

Example: Spatial interpolation methodsSince the world is so complex, revealing more detail the closer we look, it is necessary to make choices about

what to represent, at what level of detail, over what period of time

Digital Representation of Geography

Binary representation

Every item of useful information about the Earth’s surface is ultimately reduced to some combination of 0s and 1s.

The representation itself (0s and 1s) is rarely seen by the user, instead, the user sees a view designed to present the contents in a meaningful form.

Geographic representations are among the most ancient…

Sketches in the dirt or on cave walls probably preceded language that could relate equivalent information…

Effective media for communication between members of a small group

Invention of the printing press in the 15th centuryKnowledge could be the common property of humanity…Major restriction: representation had to be flat…

The “Age of Discovery” (15th century)Henry the Navigator of Portugal and other explorersMaps became the most valuable medium for

Establishing new discoveriesAdministering colonial empires

A Key Issue: What to represent and how to represent it…

Any application of GIS requires clear attention to questions of what to represent, and how.

There is a multitude of possible ways of representing the geographic world in digital form,

none of which is perfect,

and none of which is ideal for all applications.

Place, Time, and Attributes…

Geographic data link place, time, and attributes.Time is optional in GIS

Time can be omitted in many casesExample: elevation

Time is essential in some casesExample: atmospheric temperature

Attributes are classified as:Nominal

Serves to identify one entity from anotherExamples: place namesCan include: Numbers, letters, colors, names, etc.IMPORTANT: It makes no sense to apply arithmetic operations to this class of data!

Attributes, Continued

OrdinalValues have a natural orderExample: Class 1 is best, Class 2 is not as good, etc.IMPORTANT: Adding, averaging, or taking ratios makes no sense with this class of data!Medians are legitimate and can be a useful value

IntervalDifference between values makes sense.Example: Celsius temperature scale

It makes sense to say that 30 and 20 areas different as 20 and 10

However, 20 is not twice as hot as 10Any scale data with an arbitrary zero point

Attributes, Continued

RatioRatios between values makes sense...Example: Weight (100 lb is twice as heavy as 50 lb)

Cyclic, or DirectionalSpecial type of data with special problems

Example: Compass Directions0 degrees to 359 degreesCannot average all values

(ex: (359 + 1)/2 = 180)Example: flow directions on linear segments

Degrees, Minutes, Seconds VS. Decimal Degrees

The Fundamental Problem with representations

The world is infinitely complex, but computer systems are finite. Therefore, representation is all about the choices that are made in capturing the knowledge about the world.

A representation must be partial…Limit level of detailIgnore changes through timeIgnore certain attributesSimplify by classifying into ranges, etc.

Example: spatial resolution for representation of worldwide elevation

the Earth’s surface covers 500 million sq km, therefore, 10km resolution = 5 million cells of info, 1km resolution = 500 million cells of info, and 1 meter resolution = 500 trillion cells of info

Two Conceptual Schemes for Representation of Geography

A fundamental choice has to be made between representing the geographic world as:

Discrete ObjectsOr

Fields

The Discrete Object View

Represents the world as objects with well-defined boundaries in empty space.

Objects are instances of generally recognized categories.Objects can be counted

Good Examples: biological organisms, manufactured objects

Messy Examples: mountains (where does it start/end?)

Offers powerful way of linking attribute information about each object (row in a data table corresponds to each object and the columns hold attribute data on each object)

Dimensionality in the Object View

Two-dimensional objectsareas (most often referred to as polygons)Examples: lakes, administrative regions

One-dimensional objectsLinesExamples: roads, rivers

Zero-dimensional objectsPointsExamples: individual animals, buildings

Limitations of the Object View

In reality, all objects are 3-dimensional, so representation in fewer dimensions is just an approximation.

Ability of GIS software to handle true 3-D objects as volumes is very limited.

Can assign height attributes to each coordinate that describes the object (sometimes called “2.5D”)

2-Dimensional networks handle overpasses by assigning turning options at each intersection (no turns= overpass)

Works poorly for continuous surfaces

The Field View

Continuous surfaces are represented better in the field view.

In this view the geographic world can be described by a finite number of variables, each measurable at any point on the Earth’s surface, and changing in value across the surface.

Fields are distinguished by what varies, and how smoothly.

Field or Object View?

Fields can represent continuous variation across space OR lines

Examples that may also be represented in the object view:ElevationPopulation densityLand useSoil typeTraffic density along a road networkLakes (degrees of “lakeness” – assign every point a value describing the condition….dry, sometimes flooded, etc.)

Raster and Vector Data Models

Fields and Discrete Objects are conceptual views.Two methods are used to reduce geographic phenomena to forms that can be coded into computer databases, called Raster and Vector data models.

Raster Representation ModelGeographic space is divided into an array of cells (or pixels)The cells are usually squareVariation is expressed by assigning values to cells

Vector Representation ModelPoints, Lines, Areas (Polygons)

Raster Data

Spatial resolution of raster data = length of a cell side

Square cells do not fit together neatly on a curved surface.

When information is presented in raster form all detail about variation within cells is lost, and instead the cell is given a single value.

Must establish rules for assigning cell valuesMajority or plurality methodCentral point of the cell method

Common form of raster data is satellite imagery.

Vector Data

Points are captured as x and y coordinates.

Lines are captured as points connected by precisely straight lines (also called polylines when representing a curved line)

Areas captured by as a series of points (vertices) connected by straight lines (also called polygons).

Raster vs. Vector

“Raster is vaster, and vector is correcter”Raster model requires very small cells sizes to accurately represent the location of features (lots of cells with attribute data for every cell).Vector model just requires that the vertices that make up the line or polygon be stored.

Apparent precision of vector is often an unreasonable representation of the spatial accuracy of the data.Issues:

Volume of Data Sources of dataApplicationsSoftwareResolution

Paper Maps

Analog representation, or physical model of the world scaled to fit the size of the paperLimitations include: static, hard to update, limited 3-D

Scale or Representative Fraction is defined as the ratio of the distance on the map to the distance on the Earth’s surface.Example:1:24,000 (1 inch on the map represents 24,000 inches on the surface of the Earth, AND, 1 foot on the map represents 24,000 feet on the surface, or 1 meter:24,000 meters, etc.)Scale for a digital geographic database refers to the scale of the source paper map.Large scale vs. small scale maps

1:2000 map is a “larger scale” map than a 1:100,000 map

Chapter 5 - Georeferencing

“Atomic element” of geographic informationLocation (essential)Time (optional)Attributes (usually included)

Without locations, data is non-spatial (or aspatial)

The act of assigning locations to informationCommon Terms: georeference, geolocate, geocode

Primary Requirements

A georeference must be uniqueOnly one location associated with a given georeferenceNo confusion about the location that is referencedMeaning must be shared among all that work with the infoCan link different kinds of info to based on a common location

To be most useful, georeferences should stay constant through time.

Georeferencing Concepts

Every georeference has an associated spatial resolution equal to the size of the area that is assigned.

note: mailing address, state, zip, etc. can vary in size

Many systems of georeferencing are unique only within an area or domain of the Earth’s surface.

Examples: City Names…there is a Jacksonville in Florida and in North Carolina…and street names…there are many Main Streets, but only one per city….

Metric Georeferences

Based on measurements instead of namesExamples: latitude and longitude, UTM coordinates, etc.

Biggest Advantage: potential for infinitely fine spatial resolution limited only be the measuring devices that we have…

Another advantage: from measurements of two or more locations, it is possible to compute distances

Note: other types of georeference systems, like street addresses, only order locations

Placenames

Simplest, most ancient method

Language extends the usefulness for georeferencingEx: “between” two places or “near” a place or 1 mile north of some place

But, usefulness is limited because:Meanings vary between people and within context usedCoarse resolution (ex: “within Asia” is vague)Placenames can vary with time

Postal Addresses and Postal Codes

Assumptions:Every dwelling and office is a potential destination for mailDwellings and offices are arrayed along roads and numbered accordinglyRoads have names that are unique within local areasLocal areas have names that are unique within larger regionsRegions have names that are unique within countries

Zip codes vary in size (and are changed frequently), but are useful for mapping summarized data

Postal Addresses don’t always work…

Don’t work for natural features

Don’t work when dwellings are not numbered consecutively along streets (such as in Japan, where the number reflects date of construction).

Don’t work well in high-rise buildings where many dwellings occupy the same horizontal space…

Linear Referencing Systems

Often used for managing transportation infrastructure

Defines location on a network by measuring the distance from a defined point of reference along a defined path in the network.

Closely related to the street address system, but provides a more explicit measurement of distance

Cadasters

The Cadaster is the map of land ownership in an area

The property appraiser maintains the cadastral map for purposes of taxing land and keeping public records of land ownership…

Parcels of land have unique numbers or codes that are consistent through time, but hard to remember!

Public Land Survey System (PLSS)

Used to survey the vast areas beyond the “original colonies” beginning in the early 19th CenturyA metric system of georeferencing (with some problems due to curvature of the earth…)Description of property location by section/township/range

Prime Meridian (north-south line)Ranges (rows that are six miles apart and perpendicular to the prime meridian line, N or S)Townships (columns that are six miles apart form blocks that are on either side (E or W) of the prime meridian)Sections (each township is divided into 36 sections, roughly 640 acres each (5280 ft/mi and 43560 sq. ft. / acre)Describe smaller parcels with quarter sections, etc.

Latitude and Longitude

The most comprehensive systemPotential for very fine spatial resolutionCan compute distances between locationsSupports other forms of spatial analysis

Often called the geographic system of coordinates

Longitude Defined

Based on the axis of the Earth’s rotationCenter of mass lies on this axis

The plane through the center of mass perpendicular to the axis of rotation is the equator

Slices through the Earth parallel to the axis and perpendicular to the plane of the equator define lines of constant longitude.

A line of constant longitude is called a meridian.

Zero longitude (the prime meridian) goes through a line at the Royal Observatory in Greenwich, England

Measuring Longitude

All longitude slices are measured as angles from the prime meridian

360 total degrees 180 degrees West or East

East longitudes are stored in computers as positive numbersWest longitudes are stored as negative numbers

60 minutes in a degree60 seconds in a minuteUse decimal degrees to accommodate computersDecimal Degrees = Degrees + minutes/60 + seconds/3600

The Earth is not a perfect sphere…

The term ellipsoid or spheroid is used to describe the shape…The Earth is slightly flattened, such that the distance between the Poles is about 1/300 less than the diameter at the Equator.

Many ellipsoids have been used over the years…The WGS84 ellipsoid (the World Geodetic System of 1984) is the basis for most new mapping

Or the North American Datum of 1983 (NAD83, NAD83 HARN, etc.)…

Others are still used by other countries—be careful….

Latitude Defined

If we draw a line through any point on the Earth’s surface that is perpendicular to the ellipsoid at that location, then measure the angle made by this line with the plane of the Equator, this angle defines the latitude of that point.

Angles vary from 90 degrees North to 90 degrees South.North angles are stored in computers as positive numbers and South angles as negative numbers.

Lines of constant latitude are called parallels

Distances in longitude and latitude

Latitude distances are constantTwo points on the same meridian, separated by one degree of latitude are about 111 km apart (1/360th)One minute of latitude ~= 1.86 km (a nautical mile)One second of latitude ~= 30 meters

Longitude distances vary Meridians converge on the poles, henceLines are farthest apart at the equator (111 km)

One degree of longitude ~= 96 km at 30 degrees North or South (~58 miles)

~ 78 km at 45 degrees~ 55 km at 60 degrees

Map Projections

Much work in GIS deals with a flattened or projected EarthPaper is flat, rasters are flat, etc.

A map projection transforms a position identified by latitude and longitude into a position in Cartesian coordinates (x,y)

It is very important to know the map projection of a data set.Projections distort at least one of these properties

Shape AreaDistanceDirection

Projection Properties and Classes

A map projection can have either property (but not both):Conformal – preserves local shape

(useful for navigation)Equal area – preserves area measurements

(useful for analysis)Other projections are termed equidistant and true-direction

Three major classes of projectionsCylindricalAzimuthal or planarConic

Graticule shows how the lat/long lines map onto the projection

Using Unprojected Data

Be careful using a GIS to analyze data in latitude and longitude rather than projected coordinates, because serious distortions in distance and area may result…

“Projection on-the-fly”

Common Coordinate Systems

Universal Transverse Mercator (UTM)Global or national mapping use60 zones (6 degrees of longitude for each zone)Problems:

Maps don’t fit together across zonesArbitrary definition of zones

Conformal (shape is preserved) and scale is same in all directionsStandard coordinate system used Coordinates are in meters

500,000m Easting

Common Coordinate Systems (cont.)

State Plane Coordinate SystemMore accurate than UTMCoordinates in feetNo problem with arbitrary zonesEstablished in the 1930’s, each state adopted its own map projection based on minimizing distortion

Some large states have internal zones to minimize distortion even more

Most GIS software have the named projections stored so that it is relatively easy to convert between the most common map projections.

Chapter 4 - The Nature of Geographic Data

Reminder: The fundamental problem of GIS is that of selecting what to leave in and what to leave out of digital representations of the real world.

Smoothness and irregularity are important distinguishing characteristics of geographic data.

The scale or level of detail may determine whether spatial and temporal phenomena appear regular or irregular.

Spatial heterogeneity = the tendency of geographic places and regions to be different from each other.

Spatial data tend to exhibit an increasing range of values, or increased heterogeneity, with increased distance.

Isopleth and Choropleth Maps

Isopleth maps are used to visualize phenomena that are conceptualized as fields and measured on interval or ratio scales. (see Figure 4.9)

An Isoline connects points of equal attribute values…created from sample points measurements

Choropleth maps are constructed from values describing properties of non-overlapping areas.

Areas are shaded/colored to show value of variablespatially extensive variables - values are true only for entire areas (ex: total population)

Important: Can be misleading…see Figure 4.10spatially intensive variables - values that could potentially be true for every part of an area (if it is homogeneous), (ex: densities, rates, proportions)

The Lengths of Geographic Objects?

Coastline Exampleas you measure with more precision, the length gets longer…

any approximation is scale-dependent length is indeterminate

where small deviations resemble larger deviations in form, the coastline is self-similaras the path of the coast traverses space, its intricate structure comes to fill up more space than a one-dimensional straight line but less space than a two-dimensional area….as such it is said to be of fractional dimension (a fractal) between 1(a line) and 2 (an area).

Chapter 8 - Geographic Data Modeling

Decisions about the type of model to be adopted are vital to the success of a GIS project.

Levels of abstraction (see Figure 8.2)reality

(buildings, streets, wells, etc.)conceptual

discrete object or field modelslogical

raster or vector modelsdiagrams

physicalactual format of files or database tablesDependent on your selected software, etc.

Phases of GIS Modeling

First phasedefine main types of real objects to be representedchoose conceptual model

Second Phasecreation of diagrams, lists of attributes, etc. for each object to be modeleda logical model is independent of the software used

Final Phasecreate a model showing how objects will be digitally implemented in a specific GIS software packagephysical models describe the exact files or tables used

Types of Data Models Used in GIS

Computer-aided design (CAD)GraphicalImageRaster/GridVector/geo-relational topologicNetworkTriangulated irregular network (TIN)Object

Raster Data Model

Stored as an array of cells (often called a grid)Satellite images are stored as stacks of arrays representing each spectral band in the imageair photos are usually just one arrayassociated with the field conceptual modelInteger or floating point values for cells

Integer values can be associated with an attribute tableMetadata about the array often held in a file header

geographic coordinate of the upper-left corner of arraycell sizenumber of rows and columns

Primary operational problem = large size of raw datasets

Raster Compression Techniques

Compression techniques (see Box 8.1)Lossless

run-length encoding (encoding row cells with a pair of values---no. of cells with same value, value)block encoding (quadtree data structure)

lossywavelet (remove information recursively by examining patterns in the data at different scales)

highest level of data compressiononly useful for satellite images, air photos, etc.MrSID (Multiresolution Seamless Image Database)fast viewing at different scales with appropriate amounts of detail for the scale (.sid extension)

Vector Data Model

Associated with the discrete object conceptual modelpoint, line, and polygon objectssee figure 8.7

2, 3, or 4 dimensions associated with each coordinate3-D = height, 4-D for time, offsets, etc.

geographic entities are called featuresfeature table - each feature occupies a row and each property or attribute of the feature occupies a column

Two types of featuressimpletopologic

Simple Features

Also called spaghetti features lines and polygons can overlapthere are no relationships between any of the objectsExample: ESRI shapefiles

Advantageseasy to create and storedraws quickly on the screen

Disadvantageslack of any connectivity relationships (limits network and polygon adjacency analysis methods)inefficient for modeling phenomena conceptualized as fields because adjacent boundary coords are stored twicepotential for overlap can cause problems (ex: ownership)

Topologic Features

Simple features that are structured using topologic rules

Topology is the science and mathematics of relationships used to validate the geometry of vector entities, and for operations such as network tracing and tests of polygon adjacency

Relationships are non-metric (qualitative) properties of geographic objects that remain constant when geographic space is distorted.

Example: When a map is “stretched” , properties like distancechange, but topological properties like adjacency do not.

Line data are also sometimes called 1-cell, arc, edge, or linkpolygon data sometimes called 2-cell, area, or face

Topology and Line Features

Example uses related to line featuresforce all line ends that are within a user-defined distance to be snapped together so that they have the same coordinate values and share a single node (for instance, snapping tolerance can be set during digitizing)where there are overlapping lines, place a node at the point of intersectioncan have attributes associated with each node

ex: turn tables (no left turn, etc.)maintain direction info with each line (tracing analysis)

info on “from node” and “to node” is maintained

Topology and Polygon Features

In a topologically structured polygon data layer, each polygon is defined as a collection of lines, that in turn are made up of an ordered list of coordinates (nodes and vertices).SEE Figure 8.8

polygon-line list table and line coordinate list table a line number may appear more than once in the polygon-line list table, but the actual coordinates for the line are only stored once in the line coordinate table

advantages: avoids gaps (slivers) and overlapsfewer coordinates are stored compared to “simple features” model

primary disadvantage is that drawing time is slower

Planar Enforcement and Contiguity

“Planar enforcement” implies that:all space on a map must be filledany point on a map must fall in only one polygon, in other words, there can be no overlapsphenomenon is conceptualized as a fieldspecial cases include “islands” and the “universal polygon”

“Contiguity” or adjacency between polygonsalso defined during the process of topologic structuringlist of polygons on the left and right-hand side of each line, in the direction defined by the list of coordinatesSEE Figure 8.9

Chapter 10 - Creating and Maintaining Geographic Databases

Standard DBMS (Data Base Management Systems) functionsstandard data models data loading toolstools to index standard database data typesstructured query language (SQL)security (controlled access to parts of database)controlled updating (mutli-user transaction management)backup and recovery utilitiesdatabase administration toolsapplications for creating, using, and maintainingprogrammable API (application programming interface)

Chapter 11 - METADATA

“Data about data”

We need metadata to be able to:automate the process of search and discovery over distributed archives…(ex: www.geographynetwork.com)

similar to library’s catalog, but can also search for data based on location

determine whether a dataset, once discovered, will satisfy the user’s requirements

sufficient spatial resolution?Date of creation?Spatial extent?

METADATA

Provides the information needed to handle the dataset effectively.

Tech specs on formatmap projection

provides useful information about the contents of the dataset

attribute definitions, etc.

Metadata generation can be expensive and time-consuming

METADATA Standards

To be most useful, standards are useful

FGDC StandardsUS Federal Geographic Data Committee’s Content Standards for Digital Geospatial Metadata, 1993

Content standard - describes the items that should be included but not the exact format or structuresee Box 11.2 for a list of types of content

Metadata LITE - limited set of properties that is cheaper to produce but still useful for search/discovery

see Box 11.3

Chapter 13 - Visualization and User Interaction

Maps can be used as decision support toolsto create, support, or reinforce a particular message

GIS (or just maps) can mislead viewers

Historically, many maps were created to support national interests (warfare, inventory of territories, trading routes, etc.)

time frame for changes was relatively slowToday, time frame for change is rapid

Limitations of Paper Maps

Paper Maps are of fixed scalegeneralization of detail is not recoverableGIS can allow different levels of detail at different scales

Paper Maps are of fixed extentGIS can be seamless (no adjoining maps to deal with)

Paper Maps present a static viewGIS can be linked to dynamically changing data

Paper Maps are flatGIS can include 2.5D data and visualization

Paper Maps are limited to what information is on the mapGIS allows supplementation with further data

Paper Maps provide only one map-producer centric view of the world, GIS users can create their own view

Attribute Representation

Many conventions for symbols exist Ex: highway shields, etc. (symbol sets in ArcMap)

Graphic primitivesgraduated size of symbols

principally used for ordinal or interval/ratio datavalue and saturation of color

variation in attribute valueshue - use of colors

discriminate between nominal categoriesshape or orientation of symbols

used to relate some value of attributearrangement, texture, focus

within/between-symbol properties, patterns

Attribute Representation (cont.)

Standard labeling method issuescentroid placement, splines, overlap, alignment

Issues in choropleth mappingvisual implication of implied within-zone uniformity

Dot Density maps represent relative density of zonally averaged data (not location of point events)

Proportionally-sized circlesproblem of overlapping circles in “busy areas” of map

Classification of Interval and Ratio Data

Interval = difference between values makes senseex: temperature

Ratio = ratios between values makes senseex: weight

Natural Breaksapparently natural groupings of data values

deductive assignment - based on known breakpointsex: arid, semi-arid, temperate, humid, etc.

inductive assignment - software finds relatively large jumps in the data values

Classification of Interval/Ratio Data (cont)

Quantile Breakseach of the predetermined number of classes contains an equal number of observationscan be problematic when values with widely different values get placed in the same class, etc.can have as many classes as required

Equal Interval Breaksbest used where data ranges are familiar to user

Standard Deviationdistance of observation from the mean valuetwo-color ramps help to visualize the above/below ranges

Cartograms and Dasymetric Mapping

CartogramsDistort area or distance in the interest of some objective

Examples: subway maps (see Figure 13.9) typical objectives:make patterns more obviouspromote legibility

Dasymetric mappingancillary data sources used to improve the model of a spatial distributionSee example in Figure 13.12 - allocation of population figures to areas smaller than census tracts

Chapter 17 and 18 - GIS Management

GIS has two obvious relationships to management:

First - GIS can help manage many types of projects so as to produce a more effective, more efficient, more equitable, or more productive outcome.

Many decisions have consequences which are geographically and existing geographic variations can influence key decisions…

Second - GIS projects themselves need to be managedspecification of needsselection and procurement of toolstraining of staffetc.

Management is best when it evolves

GIS implementations should evolve to take advantage of:

new technologies internet map servershandheld GISwireless communications

organizational developments

serendipity

“Dave Says”...

To be a “Good” GIS manager, you must:stay up-to-date on technology

attend conferencesjoin local or regional User Groupssubscribe to journalsbookmark GIS websites and visit them often

attempt to understand the business objectives and processes in all departments of the company or institution

look for opportunities to “add GIS” educate others about GIS

demonstrate to anyone that will take the timepass around articles describing how others have used GIS to their advantage

always consider yourself part of a teamGIS does not “stand alone” for long….

Potential Benefits that “The Boss” will relate to...

Tell your boss that GIS can:Provide “factual information” about the location of resourcesCompute derived “facts” (…such as, the fastest route, changes in customer distribution, etc.)Help select, compress, and visualize complex information to facilitate better understanding and hence, better decision-makingCan help search for patterns and correlates of geographic distributionsCan link information from different sources in one “more intuitive” map-centric interfaceCan help predict future events that are geographically distributed

Geographic Information (GI) from a management perspective...

In the past, most GI was produced by and for governments, increasingly, GI is being developed by businesses

sometimes, GI is just “value-added” government datait’s not going to be free anymore (and no sharing…)

GI is an “experience good” that consumers have to experience in order to appreciate and value

GI does not wear out through use, though it may diminish in value as time passes…

However much it costs to collect/create, or update, the first instance of GI, the marginal costs to copy and distribute it (especially by the Internet) is negligible….

Special characteristics of the GI market

Since GI has traditionally been supplied by govt. agencies for free, many consumers are not yet used to paying for data

Some detailed GI has some of the characteristics of a natural monopoly

ex: an organization has developed a very detailed GI dataset that was very expensive to create…and they are unwilling to distribute for free…and all costs are “sunk”

“Geographic Framework Information” = it may be in the best interest of everybody to use a standardized data set

Many GI data sets don’t change very fast…consumers may not need to buy updated data very often…

Special characteristics (cont.)

The value of GI also depends on the skills of the user and the available of softwareValue of a particular dataset varies with the userBecause metadata was not a priority in the past, we often know very little about the fitness of a dataset for a purpose.The legal implications of data quality have not yet been fully tested in court…Many “value-added” GI products are centered around providing standardized data sets and analysis methods that are appropriate for the data provided…since many consumers don’t have the skills, or the time, or the knowledgeThe GI market is not efficient…consumers do not fully understand the market and there are major distortions due to subsidies, legal constraints, etc. that vary by country, etc.

Advantages of the WWW for GIS Managers

The ease of setting up and using “information location tools”clearinghouses or geolibraries

The possibility to preview simplified versions of datasetsto determine suitability for purpose (quality, etc.)

The capacity for customizing applications for the needs of a specific market or group

inexpensive way to distribute wide array of applicationsIts ability to transfer data at a very low cost

share data without requiring staff to duplicate, mail, etc.The ability to transfer costs to the user from the producer

let them make their own maps!Efficient business method (charging for data/services, etc.)Familiarity of web interface for users--less training needed

G-Business

The rise of the commercial sectoruntil recently most GI was produced by governmentmany agencies now outsource data creationsome governments now charge for data

ISSUE - cost of reproduction vs. cost of productionGI as a business asset

can be protected by copyrightoften encapsulated with software to give it an advantagede facto data standards as a result of major vendors

Information Ownership?

Can geographic data, information, and knowledge be regarded as property?

Yes, but who owns it can be difficult to defineex: personal data on spending habits

Can geographic “facts” properly by protected?in USA, factual information collected by “ the sweat of the brow” -- as opposed to original, creative activities --is not protectable by copyright law.ISSUE - each representation of the same fact involves some art in the creation (each version is different…)

what is it about a compilation of data that is sufficiently original to merit copyright protection?

Information Ownership?

Is GI collected directly by a machine, such as a satellite sensor, protectable?

Very expensive to collect, hence few suppliersStrongest and easiest enforcement of copyrights

What is the “half-life” of GI?Varies by information type and applicationhistorical information can have valuecyclic transiency of value

ex: Census data loses value over 10 years until the next set of data is available, then it is valuable again for comparison analysis

Information Ownership?

How can you prove theft of your data or information?Watermarking

obvious - like watermark in paper (can be removed)non-visible - a series of groups of small numbers or colored pixels scattered apparently randomly throughout a raster dataset (“salting”) can be effective (need good documentation…)

Finger-printingex: add the occasional fictitious road, place name

Who owns information derived by adding new material to source information produced by another party?

Both you and the originator of the first dataset(s)common issue in GIS

People as a Business Asset

“Survey Says”…most GIS industry people think of themselves as technical experts…

unfortunately, this attitude means that many GIS people don’t make it into higher-level management positions

Many GIS “managers” have had little formal GIS education, instead having learned on the job over the years or by going to industry training courses

Accreditation issues are controversial and not resolved

Some Legal Issues for GIS Managers To Consider

Privacy

Government information access laws

Liability for bad decisions based on poor quality data

Geographic Framework Information

Forms the base or template for all other data sets

In the USA, the FGDC defines the following information as the US framework:

geodetic controlelevationhydrographypublic land cadaster informationdigital orthoimagerytransportationthe geography of governmental/administrative units

The End