GEO 150 - SFU

Geography

The art and science that attempts to study, explain and predict spatial distributions and variations of human activity and physical events on or near the Earth's surface

GIS (geographic information system)

- organized collection of computer hardware, software, geographic data, trained personnel and procedures for capturing, managing, analyzing and displaying, spatially referenced data to aid problem-solving

- Simple words - a visual representation of the real world

The goal of GIS

- Transform data into info and evidence

- solve problems using mapping

- extract quantitative info from maps

- enhance geo data to make meaningful to users

2 ways to organize spatial data

- Thematic - network of streets in a city (real world)

- Temporal - tree cutting at a certain time (by time)

How is GIS data arranged

- Layer based approach

- one layer contains the same type of features

- there is a geographical extent or boundary

Why is spatial location important ?

- any data that has anything to do with location information

- delivery of services - postal

- delivery of abstract - credit cards

- delivery of management - land taxes

- with an address you become a part of modern society

Geospatial reference system

identifies locations on the earth's surface

3 main categories of Geospatial reference systems

- census geography

- geocoding

- Latitude, Longitude

Census geography

- Location specified by a label or code

- geographic identifier reference system

- ex. - postal codes

Geocoding

- location specified by reference to a segment and distance from that segment to a point

- linear reference system

- ex - postal address

Longitude, Latitude

- Location specified with respect to a datum

- coordinate reference system

- ex - degrees

Perspectives of GIS

- Database

- map view

- model view

The Database view

A GIS is a unique kind of database of the world - a geographic database (geodatabase). It is an "information system for geography". Fundamentally a GIS is based on a structures database that describes the world in geographic terms.

The Map View

A GIS is a set of intelligent maps and other views that show features on the earth's surface. Maps of the underlying geographic information can be constructed and used as "windows into the database" to support queries, analysis and editing of the information- this is called geovisualization

The Model view

A GIS is a set of information transformation tools that derive new geographic datasets from existing datasets. These geoprocessing functions take info from existing datasets, apply analytic functions and write results into newly derived datasets.

Critiques of GIS

- expensive

- time consuming

- time flows and changes

- privacy

- a tool that controls the masses ( changing )

- not all perspectives

Spatial thinking

- Finding meaning in shape, size, orientation, location, direction or trajectory of objects, processes or phenoma

- Spatial data and questions fuel spatial thinking which results in spatial solutions

Spatial concepts a GIS can answer

- Location

- Condition

- Trends

- Routing

- Patterns

- Modeling

Maps

- Primary output of GIS analysis

- scaled representation or model of geographic reality portrayed using a selected set of features on a flat medium

2 most common types of Maps

- Topographic - natural features on surface of the earth

- Thematic - one specific theme

Map Creation process

Real world - map maker interpretation of world - map - map reader interpretation of the world

Map Scale

- Map scale becomes important when info about Earth has to be represented on a flat map

- in defining an appropriate scale, we are also determining the map info that can be included on the map

- a scale defines the map info that can be included on the map

- a scale defines the ratio between distance of a map and corresponding distance on ground

3 types of Scales

- Functional scale - numerical expression

- verbal scale - written description

- graphic scale - calibrated bar on line

Generalization (scale of relevance)

- Process of choosing which features to represent on map and how they will be represented

- 5 types

- classification

- simplification

- exaggeration

- symbolization

- Induction

Classification

- Expressing key characteristics of distributions

- grouping similar points together

Simplification

Determining important characteristics of features attributes

Exaggeration

enlarging or altering the features in order to capture the real world importance

symbolization

assigning graphic marks on the maps to features from the real world

induction

making influence on relationships among features on the map

3 hierachies in Map Design

- Target Audience - what we want to portray

- map components - scale bar, legend , etc

- arranging features - position, layout, visuals

Lettering

Process of selecting a type face design, preparing names, placing it at the right position (top right preferred)

Graphic Variables

shape, colour, size, texture

visual variables

priority, distance, order, quality

Symbology

- The process of rendering the graphic variables.

- in the vector data model the colour, and width are changed

Classifying Qualitative Spatial data

- the purpose of classification is to break down the data into categories to improve our understanding of the underlying patterns that may exist

- ex - natural breaks, equal interval, quantile

Georeferencing

Georeferencing is the principles and process of transforming spatial data from an arbitary system into a geographic or projected system

Process of Georeferencing

1. Define the correct shape of the earth

2. Project the spherical earth to a flat plane

3. Transform between coordinate system and datums

Globes

-Highly accurate

- difficult to move

- time consuming to make

- new map projections move the 3D globe to a 2D place and overcome the problems above

Mathematical shapes as models

- The shape of the earth is key in determining the relationship between digital maps and what they represent

Ellipsoid

- Ellipsoid shape and bulge account for the earth's rotation - more accurate

- Many ellipsoids existed before satellite technology

- After satellite tech, earth-centered ellipsoids became common

- ex - WGS 84, GRS 80

Geoid

- Accurately represents the earth's shape and size

- based on equipotential gravity surfaces at mean sea level

- Rock density causes the geoid to deviate from ellipsoid

- Extremely accurate representation of the earth

Datum (or control network)

- Highly accurate and well-designed arrangement of ground points

- Horizontal Datum - frame/reference for measuring locations on the surface of the earth

- Vertical Datum - provides frame/ reference for measuring elevations with respect to the mean sea level

- removing a datum is a crime and you could get 7 years in prison

Geographic Coordinate System

- Longitude, Latitude graph

- The key lines are the prime median and the equator

- related to the 3D earth shape

Projected Coordinate System

- Mapping includes determining the geographic locations of features on the earth's covered surface and the transforming these geographic locations into positions on a flat map

- makes 3D earth into flat map

How the projection distort Earth ?

- These important distortions result from sphere transformation to a place

- distortions can be in shape, size, direction, distance

What properties is it possible to retain the fidelity of

- Accurate transformation of Areas

- Accurate transformation of Angles

- Accurate transformation of Distances

- Accurate transformation of Directions

How to Project Earth ? - you need a light source

1. Gnomonic - light source is at the center of the earth

2. Stereographic - light source is at point opposite

3. Orthographic - at a considerable distance

UTM (Universal Transverse Mercator) - after we made earth into a flat plane

- UTM is a worldwide system defined in meters

- The world is divided into 60 zones, 6 degrees of longitude each from 84 N to 80 S latitude

- Zone 1 is the international dateline

- each zone divided by a central; median and the equator (N/S)

Spatial Data representation process

Representation of the real world - we decompose into information model (objects, fields) -- representation or data model ( vector, raster ) - databases ( physical model) - file structures

Objects

- collection of well defined discrete and spatially referenced objected

- well defined boundaries

- each object, identified through attribute table

- roads, streets

Field

- Events that vary continously across geographic space

- boundaries fuzzy

- space mutally exclusive and collectively exhaustive

- represented by category or value

- beach, lake, natural places

Vector Model

- Human world

- lines, point, polygon

- there is one geometry per layer in the GIS database

- If the beginning and end points of vector are the same then the vector polygon feature is created

Geometery

Branch of mathematics describing the shape, size and relative configuration of objects

Topology

- Science and mathematics studying

- properties of objects that do not change as the object is distorted ( train route map )

- it expresses the spatial relationships between connected or adjacent vector features in a GIS database

- deals with linkages between the computer entities used to represent them

Raster Model

- Natural world

- images, photos or scanned maps

- cell, pixel is basic unit

- coloums , rows

- pixels are equal size

Choropleth Map

Shows relative quantity by symbolizing area units such as countries, and municipalities, using colour

GIS Data Sources

- Can link and store data from multiple sources

- maps, tables, images, user input, digital products, reports

What is Data Quality based off ?

- Overall suitability of dataset for a specific purpose

- error and uncertainty

- accuracy

- precision

- resolution

- generalization

Completeness ( Data Quality )

data must be spatially and temporally complete

Compatible

mutitple dataset used in the same project must be of the same format, scale and extent

Consistent ( Data Quality )

multiple data sets should undergo consistent methods of data capture, storage, manipulation and editing

Applicable ( Data Quality )

data must be suitable for the anaylsis or project

Meta Data

- Information about data

- identify geospatial resources

- exchange geospatial resources

- manipulate geospatial resources

- catalogue geospatial resources

- Stylesheets are used to format the metadata.

- useful when data is being exchanged and benefit decisions about quality, storage, etc

Errors

- tells us about "our confidence in what is known about the data"

- deal with the difference of the measurement from a true value

Discretization

- representing spatially continous features using point, lines, polygons

- hows is the real world mis - represented

Accuracy

Measures how close our data is compared to reality

Precision

measures the level of detail in which we record the data

Uncertainty

- "confidence about what is not known"

GIS data input sources

- Keyboard entry - entering value into tables/ templates

- manual digitizing - digitizing tablet, point mode, stream mode

- Automatic Digitizing - using a large format scanner

- Data Transfer - data from a GPS, importing existing data

- Scanning - digitizing

GPS (global positioning system)

- Constellation of earth-orbiting satellites maintained by USA for the purpose of defining geographic positions on and above the surface of the earth

- not accurate, they contain errors especially when the instrument is not a dedicated one

GNSS

Global Navigation Satellite System

- Space segments - satellites

- control segment - base stations

- user segment - gps receivers

Multipath Errors

- Signalling coming directly from the satellite and reflected off other objects interfere and create location errors

- how to fix - receivers filter the signals and determine the strongest one

Dilution of Precision

- Geometery of satellites are not equally spread out

- no solution

How to reduce location errors

To reduce location errors is to take simple averages, over time the average of a series of location values will give the best estimate of the real location value

GIS

Visual represenation of the real world

Selective ability

the way signals from the gps satellites in orbit around the earth are masked

Cartography

science or art of making maps

GPS can support ...

- digital compass

- store landmarks

- dynamic routing

- mapping applications

T/F - Spatial data can only come from physical data

False, It can be from many sources such as population census, social media data, cell phone data, etc.

T/F - The GIS is only meant to store data

False, it allows us to find solutions to problems

quantile classification

Distributes the data so that an equal number are in each bin

Natural breaks classification

bins are bassed on natural groupings within the data

equal interval

divides the range of attribute values into equal-sized bins

What is the need for database management

- There is a lot of data, which causes overloads, anxiety and fatigue

- Database management is a coping strategy

- It allows us to find meaningful information for decision-making purposes

What is a database?

- A structured set of data that has some connection or relationship to each other

- May contain both non-spatial and spatial data

- In GIS we are going to deal directly with spatial data

- Descriptive info or metadata usually accompany the database

Spatial Database Management Systems ( SDMS )

Software tools and systems to achieve :

- create both attributes and spatial data

- manage the storage and retrieval of data records

- provides a GUI interface to inquire the spatial database

Database Models

set of explicit rules for representing the data objects and their relationships

Relational ( Tabuler ) Database Model

- Data is stored in and relationships are created between one or more flat files or tables where each pair of tables has a field in common, or "key"

- Data is extracted by structured query language (SQL)

Correcting Location and Attribute Errors

- All spatial data contains some level of error

- It is the responsibility of the data user to be aware of errors and make necessary corrections

- Indications of errors: impossible values, external values, internal consistency, scatter plots and trend surfaces

Management Tasks might be :

- Converting data from vector to raster and vice versa

- importing and exporting data between different sources

- the fancy term for this is Spatial Data Interprobability

Querying the Database

SQL ( Structured Query Language)

- Allows us to to ask questions

- uses = , <, >

- uses "and, or"

- number, dates, texts, other types

- math operations do not work

- queries can simply select records

- queries can perform advanced operations

- for spaital data we use things such as : " near to, far, from "

What capabilities does ArcGIS Online software have ?

The ArcGIS Online software has capabilities to control what happens to your data in terms of editing

Coordinate system

keeps all locations across the data layers to be in sync with each other

Digital Earth

a virtual representation of the Earth that is georeferenced and connected to the world's digital knowledge archives.

Geographic Information Science

- Philosophical, epistemological and ontological contexts of geographic information

- deals with concepts, theories and methods as well as their applications

Geographic Information Systems

Provides the infrastructure, tools and methods for tackling real world problems

Geographic Models and Algorithims

- Investigating important problems

- Scientific software that is used to represent and manipulate scientific domain objects, relationships and processes

- Converts computer information into science that advances the infrastructure of hardware and software networks and data management for problem-solving

Methods and Concepts

- Used to discover knowledge

- Methods must be objective, transparent, reproducible and verifiable for others

- Methods are systematic approaches or procedures employed to achieve a specific goal

- concepts are abstract ideas or general notions representing categories of objects, events, or phenomena.

Measurements ( Spatial Relationship )

- What are the physical distances, lengths and areas?

- vector - deals with points, lines and polygons

- vector deals with point coordinates to do the calculations

- patterns, distance, perimeter, area, recoding, cost distance

Cost Distance

- Distance travelled that takes in friction and effort

- For example: travelling on a road - it is not always the same because there are different barriers and obstacles in the way