OCTOBER17 2006

Geographic Information Systems (GIS)SGO1910 & SGO4030 Fall 2006: 

Geographic Information Systems (GIS) SGO1910 & SGO4030 Fall 2006

Announcements: 

Announcements WUN GIS Seminar: "Representations of space-time in GIS" by Donna Pequet, Penn State University Date: Wednesday, October 18, 17.00-19.00 Place: UB (Georg Sverdrups hus) room 3514. For more information on this series: http://www.wun.ac.uk/ggisa/seminars.html

Slide3: 

http://www.wun.ac.uk/ggisa/seminars.html

Other Resources: 

Other Resources GIS Club GIS Day – November 15, 2006 ESRI Brukerkonferanse (February 2007)

Midterm Quizzes: 

Midterm Quizzes The first quiz will be handed back to you at the end of class today. The next midterm quiz is in two weeks (on Oct. 31), and will cover chapters 6,9,10,12 and three lectures.

Slide8: 

22. Geographic techniques can be applied to non-geographic spaces. True ”But many of the methods used in GIS are also applicable to other non-geographic spaces, including the surfaces of other planets, the space of the cosmos, and the space of the human body that is captured by medical images” (p. 8)

Slide10: 

Jeg er malerikonservator. I 2004-2005 designet og ledet jeg et prosjekt på Munch-museet som skulle svare på to spørsmål: hva vil det koste å sette kommunens Munch-malerier i stand, og hvordan skal arbeidet prioriteres. Kommunen eier omlag 1150 Munch-malerier, og alle skulle vurderes i dette prosjektet, kalt Konserveringsplanprosjektet. Til å tilstandsregistrere og tidsberegne behandlingen av maleriene brukte jeg GIS ArcView. Prioriteringen av behandlingen av Munch-maleriene ble utarbeidet som en matrise basert på kunsthistorisk verdi og tilstand (GIS).

Slide12: 

Painting on church ceiling (1270 AD) -- Vestre Slidre, Oppland

Oslo Project: 

Oslo Project The aim of this project is to integrate what you have learned in GIS lectures and labs through practical experience. Working in groups of three or four, you will address a spatial issue in Oslo (e.g. resource distribution, inequality) through the collection, mapping and analysis of data, which will then be presented in a concise professional report that is no more than 12 pages long, including maps and references.

Groups: 

Groups You may select your own group, or we can create groups for you. Groups should be established over the next two weeks – send me an email when your group is formed. Graduate students have the option of doing an independent project related to their own research, or the Oslo project in a group.

Acquiring Map Data: 

Acquiring Map Data Data sources in Norway

Global Positioning Systems (GPS): 

Global Positioning Systems (GPS) Sources of information: http://www.trimble.com/gps/ http://www.colorado.edu/geography/gcraft/notes/gps/gps.html#DODSystem http://home.no.net/perfrode/Kart/hva_er_gps_paa_norsk.htm

GPS is a Satellite Navigation System : 

GPS is a Satellite Navigation System GPS is funded by and controlled by the U. S. Department of Defense (DOD). While there are many thousands of civil users of GPS world-wide, the system was designed for and is operated by the U. S. military. GPS provides specially coded satellite signals that can be processed in a GPS receiver, enabling the receiver to compute position, velocity and time. Four GPS satellite signals are used to compute positions in three dimensions and the time offset in the receiver clock.

Space Segment : 

Space Segment The Space Segment of the system consists of the GPS satellites. These space vehicles (SVs) send radio signals from space.

Space Segment (cont): 

Space Segment (cont) The nominal GPS Operational Constellation consists of 24 satellites that orbit the earth in 12 hours. The satellite orbits repeat almost the same ground track (as the earth turns beneath them) once each day. The orbit altitude is such that the satellites repeat the same track and configuration over any point approximately each 24 hours (4 minutes earlier each day). There are six orbital planes (with nominally four SVs in each), equally spaced (60 degrees apart), and inclined at about fifty-five degrees with respect to the equatorial plane. This constellation provides the user with between five and eight SVs visible from any point on the earth.

Slide26: 

GPS Satellites Name: NAVSTAR Manufacturer: Rockwell International Altitude: 10,900 nautical miles Weight: 1900 lbs (in orbit) Size:17 ft with solar panels extended Orbital Period: 12 hours Orbital Plane: 55 degrees to equatorial plane Planned Lifespan: 7.5 years Current constellation: 24 Block II production satellites Future satellites: 21 Block IIrs developed by Martin Marietta

Latest Development : 

Latest Development Galileo, Europe's contribution to the Global Navigation Satellite System (GNSS), is creating a buzz in the Global Positioning Systems (GPS) applications market. With its advantages of signal reliability and integrity, it is poised to drive European GPS applications markets. Unlike its US counterpart, Galileo is envisioned as being independent of military control and is expected to be harnessed for widespread commercial and civilian purposes. (Space Daily, Dec. 18, 2003)

From Wikipedia…: 

From Wikipedia… The system should be operational by 2010, two years later than originally anticipated. The European Commission had some difficulty trying to secure funding for the next stage of the Galileo project. European states were wary of investing the necessary funds at a time of economic difficulty, when national budgets were being threatened across Europe. Following the September 11, 2001 attacks, the United States Government wrote to the European Union opposing the project, arguing that it would end the ability of the U.S. to shut down GPS in times of military operations. On January 17, 2002 a spokesman for the project somberly stated that, as a result of U.S. pressure and economic difficulties, "Galileo is almost dead." [1] A few months later, however, the situation changed dramatically. Partially in reaction to the pressure exerted by the U.S. Government, European Union member states decided it was important to have their own independent satellite-based positioning and timing infrastructure. All European member states became strongly in favour of the Galileo system in late 2002 and, as a result, the project actually became over-funded, which posed a completely new set of problems for the European Space Agency (ESA), as a way had to be found to convince the member states to reduce the funding.

A Happy Ending??: 

A Happy Ending?? In June 2004, in signed agreement with the United States, the European Union has agreed to switch to a range of frequencies known as Binary Offset Carrier 1.1, which will allow both European and American forces to block each other's signals in the battlefield without disabling the entire system. The European Union also agreed to address the "mutual concerns related to the protection of allied and U.S. national security capabilities.” International involvement: China, Israel, Ukraine, South Korea, India, Morocco, Saudia Arabia, etc.

Control Segment: 

Control Segment The Control Segment consists of a system of tracking stations located around the world.

Slide31: 

The Master Control facility is located at Schriever Air Force Base (formerly Falcon AFB) in Colorado. These monitor stations measure signals from the SVs which are incorporated into orbital models for each satellites. The models compute precise orbital data (ephemeris) and SV clock corrections for each satellite. The Master Control station uploads ephemeris and clock data to the SVs. The SVs then send subsets of the orbital ephemeris data to GPS receivers over radio signals.

User Segment: 

User Segment The GPS User Segment consists of the GPS receivers and the user community. GPS receivers convert SV signals into position, velocity, and time estimates. Four satellites are required to compute the four dimensions of X, Y, Z (position) and Time. GPS receivers are used for navigation, positioning, time dissemination, and other research. Navigation in three dimensions is the primary function of GPS. Navigation receivers are made for aircraft, ships, ground vehicles, and for hand carrying by individuals.

Slide36: 

Precise positioning is possible using GPS receivers at reference locations providing corrections and relative positioning data for remote receivers. Surveying, geodetic control, and plate tectonic studies are examples.

Here's how GPS works in five logical steps: : 

Here's how GPS works in five logical steps: The basis of GPS is "triangulation" from satellites. To "triangulate," a GPS receiver measures distance using the travel time of radio signals. To measure travel time, GPS needs very accurate timing which it achieves with some tricks. Along with distance, you need to know exactly where the satellites are in space. High orbits and careful monitoring are the secret. Finally you must correct for any delays the signal experiences as it travels through the atmosphere.

Triangulating : 

Triangulating Position is calculated from distance measurements (ranges) to satellites.   Mathematically we need four satellite ranges to determine exact position.   Three ranges are enough if we reject ridiculous answers or use other tricks.   Another range is required for technical reasons to be discussed later.

Measuring Distance : 

Measuring Distance Distance to a satellite is determined by measuring how long a radio signal takes to reach us from that satellite.   To make the measurement we assume that both the satellite and our receiver are generating the same pseudo-random codes at exactly the same time.   By comparing how late the satellite's pseudo-random code appears compared to our receiver's code, we determine how long it took to reach us.   Multiply that travel time by the speed of light and you've got distance.

Getting Perfect Timing: 

Getting Perfect Timing Accurate timing is the key to measuring distance to satellites.   Satellites are accurate because they have atomic clocks on board.   Receiver clocks don't have to be too accurate because an extra satellite range measurement can remove errors.

2005 Nobel Prize in Physics: 

2005 Nobel Prize in Physics Two physicists (Hall and Haensch) shared the Nobel Prize in Physics for advancing the development of laser-based precision spectroscopy, a field that opens the way to the next generation of global positioning system (GPS) navigation and ultra-precise atomic clocks.

Satellite Positions : 

Satellite Positions To use the satellites as references for range measurements we need to know exactly where they are.   GPS satellites are so high up their orbits are very predictable.   Minor variations in their orbits are measured by the U.S. Department of Defense.   The error information is sent to the satellites, to be transmitted along with the timing signals.

Slide43: 

Three satellites could be used determine three position dimensions with a perfect receiver clock. In practice this is rarely possible and three SVs are used to compute a two-dimensional, horizontal fix (in latitude and longitude) given an assumed height. This is often possible at sea or in altimeter equipped aircraft. Five or more satellites can provide position, time and redundancy. More SVs can provide extra position fix certainty and can allow detection of out-of-tolerance signals under certain circumstances.

Slide44: 

Position in XYZ is converted within the receiver to geodetic latitude, longitude and height above the ellipsoid. Latitude and longitude are usually provided in the geodetic datum on which GPS is based (WGS-84). Receivers can often be set to convert to other user-required datums. Position offsets of hundreds of meters can result from using the wrong datum.

GPS errors are a combination of noise, bias, blunders. : 

GPS errors are a combination of noise, bias, blunders.

Selective Availability (SA) : 

Selective Availability (SA) SA is the intentional degradation of the SPS signals by a time varying bias. SA is controlled by the DOD to limit accuracy for non-U. S. military and government users. SA was turned off in May, 2000!

Bias Error sources : 

Bias Error sources SV clock errors uncorrected by Control Segment : 1 meter Ephemeris data errors: 1 meter Tropospheric delays: 1 meter. The troposphere is the lower part (ground level to from 8 to 13 km) of the atmosphere that experiences the changes in temperature, pressure, and humidity associated with weather changes. Complex models of tropospheric delay require estimates or measurements of these parameters. Unmodeled ionosphere delays: 10 meters. The ionosphere is the layer of the atmosphere from 50 to 500 km that consists of ionized air. The transmitted model can only remove about half of the possible 70 ns of delay leaving a ten meter un-modeled residual. Multipath: 0.5 meters. Multipath is caused by reflected signals from surfaces near the receiver that can either interfere with or be mistaken for the signal that follows the straight line path from the satellite. Multipath is difficult to detect and sometime hard to avoid.

Blunders can result in errors of hundred of kilometers.: 

Blunders can result in errors of hundred of kilometers. Control segment mistakes due to computer or human error can cause errors from one meter to hundreds of kilometers. User mistakes, including incorrect geodetic datum selection, can cause errors from 1 to hundreds of meters. Receiver errors from software or hardware failures can cause blunder errors of any size.

Correcting Errors : 

Correcting Errors The earth's ionosphere and atmosphere cause delays in the GPS signal that translate into position errors. Some errors can be factored out using mathematics and modeling.   The configuration of the satellites in the sky can magnify other errors.   Differential GPS can eliminate almost all error.

Slide50: 

GPS technology has matured into a resource that goes far beyond its original design goals. These days scientists, sportsmen, farmers, soldiers, pilots, surveyors, hikers, delivery drivers, sailors, dispatchers, lumberjacks, fire-fighters, and people from many other walks of life are using GPS in ways that make their work more productive, safer, and sometimes even easier.

Location: Where am I?: 

Location: Where am I? The first and most obvious application of GPS is the simple determination of a "position" or location. GPS is the first positioning system to offer highly precise location data for any point on the planet, in any weather. That alone would be enough to qualify it as a major utility, but the accuracy of GPS and the creativity of its users is pushing it into some surprising realms.

Navigation: Where am I going?: 

Navigation: Where am I going? GPS helps you determine exactly where you are, but sometimes important to know how to get somewhere else. GPS was originally designed to provide navigation information for ships and planes. So it's no surprise that while this technology is appropriate for navigating on water, it's also very useful in the air and on the land. The sea, one of our oldest channels of transportation, has been revolutionized by GPS, the newest navigation technology.

Slide53: 

By providing more precise navigation tools and accurate landing systems, GPS not only makes flying safer, but also more efficient. With precise point-to-point navigation, GPS saves fuel and extends an aircraft's range by ensuring pilots don't stray from the most direct routes to their destinations. GPS accuracy will also allow closer aircraft separations on more direct routes, which in turn means more planes can occupy our limited airspace. This is especially helpful when you're landing a plane in the middle of mountains. And small medical evac helicopters benefit from the extra minutes saved by the accuracy of GPS navigation.

Slide54: 

Finding your way across the land is an ancient art and science. The stars, the compass, and good memory for landmarks helped you get from here to there. Even advice from someone along the way came into play. But, landmarks change, stars shift position, and compasses are affected by magnets and weather. And if you've ever sought directions from a local, you know it can just add to the confusion. The situation has never been perfect. Today hikers, bikers, skiers, and drivers apply GPS to the age-old challenge of finding their way.

Slide55: 

“In 1994 Norwegian Borge Ousland reached the North Pole after skiing 1000 kilometers from Siberia alone and unsupported. For this incredible challenge Børge carried a bible to read, some Jimi Hendrix to listen to, and a Trimble Scout GPS receiver to help find his way.”

Tracking: 

Tracking Commerce relies on fleets of vehicles to deliver goods and services either across a crowded city or through nationwide corridors. So, effective fleet management has direct bottom-line implications, such as telling a customer when a package will arrive, spacing buses for the best scheduled service, directing the nearest ambulance to an accident, or helping tankers avoid hazards. GPS used in conjunction with communication links and computers can benefit applications in agriculture, mass transit, urban delivery, public safety, and vessel and vehicle tracking. So it's no surprise that police, ambulance, and fire departments are adopting GPS-based AVL (Automatic Vehicle Location) Manager to pinpoint both the location of the emergency and the location of the nearest response vehicle on a computer map. With this kind of clear visual picture of the situation, dispatchers can react immediately and confidently.

Timing: 

Timing Although GPS is well-known for locating, navigation, and tracking, it's also used to disseminate precise time, time intervals, and frequency. Time is a powerful commodity, and exact time is more powerful still. Knowing that a group of timed events is perfectly synchronized is often very important. GPS makes the job of "synchronizing our watches" easy and reliable. There are three fundamental ways we use time. As a universal marker, time tells us when things happened or when they will. As a way to synchronize people, events, even other types of signals, time helps keep the world on schedule. And as a way to tell how long things last, time provides and accurate, unambiguous sense of duration. GPS satellites carry highly accurate atomic clocks. And in order for the system to work, our GPS receivers here on the ground synchronize themselves to these clocks. That means that every GPS receiver is, in essence, an atomic accuracy clock.

Mapping: 

Mapping Using GPS to survey and map it precisely saves time and money in this most stringent of all applications. Today, GPS makes it possible for a single surveyor to accomplish in a day what used to take weeks with an entire team. And they can do their work with a higher level of accuracy than ever before. GPS technology is now the method of choice for performing control surveys, and the effect on surveying in general has been considerable. GPS pinpoints a position, a route, and a fleet of vehicles. Mapping is the art and science of using GPS to locate items, then create maps and models of everything in the world. Mountains, rivers, forests and other landforms. Roads, routes, and city streets. Endangered animals, precious minerals and all sorts of resources. Damage and disasters, trash and archeological treasures. GPS is mapping the world.

Geographic Databases: 

Geographic Databases

A GIS can answer the question: What is where?: 

A GIS can answer the question: What is where? WHAT: Characteristics of attributes or features. WHERE: In geographic space.

A GIS links attribute and spatial data: 

A GIS links attribute and spatial data Attribute Data Flat File Relations Map Data Point File Line File Area File Topology

Flat File Database: 

Flat File Database Attribute Attribute Attribute

Arc/node map data structure with files: 

Arc/node map data structure with files Figure 3.4 Arc/Node Map Data Structure with Files. 1 1,2,3,4,5,6,7 Arcs File POLYGON “A” A : 1,2 , Area, Attributes File of Arcs by Polygon 1 2 3 4 5 6 7 8 9 10 11 12 13 1 x y 2 x y 3 x y 4 x y 5 x y 6 x y 7 x y 8 x y 9 x y 10 x y 11 x y 12 x y 13 x y P o i n t s F i l e 1 2 2 1,8,9,10,11,12,13,7

What is a Data Model?: 

What is a Data Model? A logical construct for the storage and retrieval of information. Attribute data models are needed for the DBMS. The origin of DBMS data models is in computer science.

Definitions: 

Definitions Database – an integrated set of data on a particular subject Geographic (=spatial) database - database containing geographic data of a particular subject for a particular area Database Management System (DBMS) – software to create, maintain and access databases

A DBMS contains:: 

A DBMS contains: Data definition language Data dictionary Data-entry module Data update module Report generator Query language

Advantages of Databases : 

Advantages of Databases Avoids redundancy and duplication Reduces data maintenance costs Applications are separated from the data Applications persist over time Support multiple concurrent applications Better data sharing Security and standards can be defined and enforced

Disadvantages of Databases: 

Disadvantages of Databases Expense Complexity Performance – especially complex data types Integration with other systems can be difficult

Characteristics of DBMS (1): 

Characteristics of DBMS (1) Data model support for multiple data types e.g MS Access supports Text, Memo, Number, Date/Time, Currency, AutoNumber, Yes/No, OLE Object, Hyperlink, Lookup Wizard Load data from files, databases and other applications Index for rapid retrieval

Characteristics of DBMS (2): 

Characteristics of DBMS (2) Query language – SQL Security – controlled access to data Multi-level groups Controlled update using a transaction manager Backup and recovery

Role of DBMS: 

Geographic Information System Database Management System Data load Editing Visualization Mapping Analysis Storage Indexing Security Query Data System Task Role of DBMS

Retrieval: 

Retrieval The ability of the DBMS or GIS to get back on demand data that were previously stored. Geographic search is the secret to GIS data retrieval. Many forms of data organization are incapable of geographic search. GIS systems have embedded DBMSs, or link to a commercial DBMS.

Types of DBMS Model: 

Types of DBMS Model Hierarchical Network Relational - RDBMS Object-oriented - OODBMS Object-relational - ORDBMS

Historically, databases were structured hierarchically in files...: 

Historically, databases were structured hierarchically in files... Norge Akershus Oppland Hordaland Asker Bærum Ski

Relational DBMS: 

Relational DBMS Data stored as tuples (tup-el), conceptualized as tables Table – data about a class of objects Two-dimensional list (array) Rows = objects Columns = object states (properties, attributes) Tuple??? A row in a relational table; synonymous with record, observation. A set of elements.

Relation Rules: 

Relation Rules Only one value in each cell (intersection of row and column) All values in a column are about the same subject Each row is unique No significance in column sequence No significance in row sequence

Table: 

Table Row = object Column = property Table = Object Class Object Classes with Geometry called Feature Classes

Relational Join: 

Relational Join Fundamental query operation Table joins use common keys (column values) Table (attribute) join concept has been extended to geographic case

Relational Data Bases: 

Relational Data Bases Purchase Record Item Date Price Customer Key Skate Board 2/1/96 49.95 John Smith 42 Baseball Bat 2/1/96 17.99 James Brown 978 Patient Record Key Check-in Check Out Room No. 42 2/1/96 2/4/96 N763 78 2/3/96 2/4/96 N712 Accident Report Date Injury Name Key Location 2/1/96 Broken Leg John Smith 42 75 Elm Street 2/2/96 Concussion Sylvia Jones 654 12 State Street 2/2/96 Cut on Ear Robert Doe 123 2323 Broad Street File File File

Most DBMS are now relational databases.: 

Most DBMS are now relational databases. Based on multiple flat files for records, with dissimilar attribute structures, connected by a common key attribute.

Retrieval Operations: 

Retrieval Operations Searches by attribute: find and browse. Data reorganization: select, renumber, and sort. Compute allows the creation of new attributes based on calculated values.

Spatial Retrieval Operations: 

Spatial Retrieval Operations Attribute queries are not very useful for geographic search. In a map database the records are features. The spatial equivalent of a find is locate, the GIS highlights the result. Spatial equivalents of the DBMS queries result in locating sets of features or building new GIS layers.

The Retrieval User Interface: 

The Retrieval User Interface GIS query is usually by command line, batch, or macro. Most GIS packages use the GUI of the computer’s operating system to support both a menu-type query interface and a macro or programming language. SQL is a standard interface to relational databases and is supported by many GISs.

SQL: 

SQL Structured (Standard) Query Language – (pronounced SEQUEL) Developed by IBM in 1970s Now de facto and de jure standard for accessing relational databases Three types of usage Stand alone queries High level programming Embedded in other applications

Types of SQL Statements: 

Types of SQL Statements Data Definition Language (DDL) Create, alter and delete data CREATE TABLE, CREATE INDEX Data Manipulation Language (DML) Retrieve and manipulate data SELECT, UPDATE, DELETE, INSERT Data Control Languages (DCL) Control security of data GRANT, CREATE USER, DROP USER

Spatial Relations: 

Spatial Relations Equals – same geometries Disjoint – geometries share common point Intersects – geometries intersect Touches – geometries intersect at common boundary Crosses – geometries overlap Within– geometry within Contains – geometry completely contains Overlaps – geometries of same dimension overlap Relate – intersection between interior, boundary or exterior

Spatial Methods: 

Spatial Methods Distance – shortest distance Buffer – geometric buffer ConvexHull – smallest convex polygon geometry Intersection – points common to two geometries Union – all points in geometries Difference – points different between two geometries SymDifference – points in either, but not both of input geometries

Spatial Search: 

Spatial Search Buffering is a spatial retrieval around points, lines, or areas based on distance. Overlay is a spatial retrieval operation that is equivalent to an attribute join.

Identify: 

Identify

Recode: 

Recode OR

Data overlay: 

Data overlay

Slide92: 

Overlay

Types of overlay operations: 

Types of overlay operations And Or Max Min

Buffer (raster): 

Buffer (raster) + 1

Buffer (vector): 

Buffer (vector)

Complex Retrieval: Map Algebra: 

Complex Retrieval: Map Algebra Combinations of spatial and attribute queries can build some complex and powerful GIS operations, such as weighting.

Summary: 

Summary Database – an integrated set of data on a particular subject Databases offer many advantages over files Relational databases dominate