1

Peter Fox

GIS for Science

ERTH 4750 (98271)

Week 2, Tuesday, January 31, 2012

Introduction to Geographic Information Systems for

Science

Contents• Introductions

• Course Outline

• Application areas

• Logistics and resources

• Assessment and assignments

• Learning objectives, outcomes

• Introduction to GIS for Science

• Next class(es)

2

Introductions• Name, major, year

• Interests, goals, outcomes

• Have you completed any *suggested* prerequisites:– Geography, cartography.– Other spatial analysis.– Mathematics background

• Questions

3

Course Outline (tentative)• Week 2 (Jan. 31/Feb 3): Topic 1/2. Introduction to GIS. Map projections and reference

systems. Introduction to MapInfo Professional software. GIS data. Preparing data for MapInfo (geocoding, reformatting). Making simple maps. Layering. Querying and selecting data. Producing thematic maps.

• Week 3 (Feb. 7/10): Topic 3. Buffering. Registering raster images. Digitizing from screen.• Week 4 (Feb. 14/17): Topic 4. Geocoding with streets/addresses. Simple interpolation

(IDW).• Week 5 (Feb 21/24): Topic 5. Introduction to geostatistics. Interpolation techniques

continued (trend surfaces, Thiesses polygons, inverse distance weighting, splines)• Week 6 (Feb. 28/31): Topic 6. Interpolation continued (variograms, kriging)• Week 7 (Mar. 6/9): Topic 7. Analysis of continuous surfaces (filtering, slopes, shading)• Mar. 13/15: no classes - spring break• Week 8 (Mar. 20/23): Topic 8. Analysis of errors• Week 9 (Mar. 27/30): Topic 9. Analysis of discrete entities• Week 10 (Apr. 3/6): Topic 10. Graphs, grouping, pie charts• Week 11 (Apr. 10/13): Topic 11. Editing attributes, manipulating objects in MapInfo• Week 12 (Apr. 17: no class) - Grand Marshall week (Apr. 30) Topic 12. Making a map from

scratch, field observations• Week 13 (Apr. 24/27): Prepare for class presentations• Week 14 (May 1/4): Topic 13. Class project presentations

4

Logistics• Class: ERTH 4750• Hours: 12pm-1:50pm Tuesday, Friday• Location: SAGE 2704• Instructor: Peter Fox - pfox@cs.rpi.edu or

foxp@rpi.edu , x4862• Contact hours: Tuesdays 2pm-3pm (or by appt)• Contact location: JRSC 1W06 or Winslow 2120• TA: Max Cane, canem@rpi.edu • Web: http://tw.rpi.edu/web/Courses/GIScience/2012

– Schedule, syllabus, reading, assignments, etc.

5

Assessment and Assignments• Via written assignments with specific percentage of

grade allocation provided with each assignment• Via individual oral presentations with specific

percentage of grade allocation provided• Via group presentations – depending on class size• Via participation in class (not to exceed 10% of

total) – this works by ‘losing’ points by not participating

• Late submission policy: first time with valid reason – no penalty, otherwise 20% of score deducted each late day

6

Assessment and Assignments• Reading assignments

– Are given almost every week– Most are background and informational– Some are key to completing assignments– Some are relevant to the current week’s class (i.e. follow

up reading)– Others are relevant to following week’s class (i.e. pre-

reading)– Undergraduates - will not be evaluated on but we will

often discuss these in class and participation in these is taken into account

– Graduates – are likely to be tested as part of assignments, i.e. an extra question

• You will progress from individual work to group work

7

Goals• To provide students an opportunity to learn

geospatial applications and tools.• To introduce relational analysis and interpretation of

spatial data and presentation on maps.• Introduce spatial database concepts and technical

aspects of query languages and geographic integration of graphic and tabular data.

• To introduce intermediate aspects of geospatial analysis: map projections, reference frames, multivariate analysis, correlation analysis, regression, interpolation, extrapolation, and kriging.

• To gain experience in an end-to-end GIS application via a term project.

8

Learning Objectives• Through class lectures, practical sessions, written

and oral presentation assignments and projects, students should:– Demonstrate proficiency in using geospatial applications

and tools (commercial and open-source).– Present verbally relational analysis and interpretation of a

variety of spatial data on maps.– Demonstrate skill in applying database concepts to build

and manipulate a spatial database, SQL, spatial queries, and integration of graphic and tabular data.

– Demonstrate intermediate knowledge of geospatial analysis methods and their applications.

9

Academic Integrity• Student-teacher relationships are built on trust. For example, students

must trust that teachers have made appropriate decisions about the structure and content of the courses they teach, and teachers must trust that the assignments that students turn in are their own. Acts, which violate this trust, undermine the educational process. The Rensselaer Handbook of Student Rights and Responsibilities defines various forms of Academic Dishonesty and you should make yourself familiar with these. In this class, all assignments that are turned in for a grade must represent the student’s own work. In cases where help was received, or teamwork was allowed, a notation on the assignment should indicate your collaboration. Submission of any assignment that is in violation of this policy will result in a penalty. If found in violation of the academic dishonesty policy, students may be subject to two types of penalties. The instructor administers an academic (grade) penalty, and the student may also enter the Institute judicial process and be subject to such additional sanctions as: warning, probation, suspension, expulsion, and alternative actions as defined in the current Handbook of Student Rights and Responsibilities. If you have any question concerning this policy before submitting an assignment, please ask for clarification.

10

Questions so far?

11

Skills needed• Geography?

– Nah, we’ll cover that

• Literacy with computers that can load/ run the relevant applications– Yep

• Ability to access internet and retrieve/ acquire data– Oh yea

• Presentation of assignments– Ditto 12

What is expected• Attend class, complete assignments (esp.

reading)

• Participate

• Ask questions

• Work both individually and in a group

• Work constructively in group and class sessions

13

Also on the web• Reading assignments – are intended to

prepare you for following lectures and may be considered materials for written assignments or project

• Assignments will be posted there– Individual– Group

• Max is your first contact for assignment questions

14

This course• GIS – in short: computer-based mapping,

analysis and retrieve of location-based data

• (in) Science, i.e. the process part – but since not all of you are in science, think of it as your application area

• Relation to GPS, Remote Sensing 15

GIS in Science (e.g.)• Think about a place (location or feature) or a

topic • Form your question (Data Science: Goal) • Find/access/analyze data (most often onto a

map• Explore the patterns and related information

presented• Enhance the data, add more data or try an

alternate analysis• Same question or a new one?• 'Repeat'

16

Introduction to GIS• The importance of information for GIS:

information is the heart of GIS.

• GIS data: spatial data (mappable data)---referring to space, occupying space, and having cartographic space; non-spatial data --- attribute data

17

Data-Information-Knowledge Ecosystem

18

Data Information Knowledge

Context

PresentationOrganization

IntegrationConversation

CreationGathering

Experience

As a consequence …• We’ll need to explore some ‘information’

concepts along the way in this course

• If you ever want more… try Xinformatics (offered in the spring, 4xxx/6xxx)

19

Introduction to GIS• GIS infrastructure: hardware, software, data,

organization, and people.

• GIS generic questions: location, areal relationship (measurement and neighborhood analysis), attributes, patterns, relationships, and trends.

• Exercise: http://www.corvallismaps.com/multimap/ Select 18TH and St. and Search, select ‘707’ and look at the returned screen

20

Introduction to GIS• GIS and GPS (see reading also)

• Relationships among objects on maps (‘computerized cartography’ plus a lot more)

• Purpose of GIS – regroup attributes, perform calculations with built-in functions, edit data, get new data, parse data, select, query,…

21

GIS Objects

22

Practical example• Point: Single coordinate pair (Fire hydrant)

• Line: 2 coordinate pairs (Road segment)

• Polyline: > 2 points, open figure (Highway)

• Region: polygons (State, county)

• Groups of regions/points/lines

• GIS is the process of dealing with the geographical relationships among these objects

23

Questions for a GIS• What exists at a certain location?

• Where are certain conditions satisfied?

• What has changed in a place over time?

• What spatial patterns exist?

• What if this condition occurred at this place? (modelling, hypothesis testing)

• (from Dawn Wright, OSU/GIS465)

24

Where is this?

25

So what’s this?

26

Map projections• Representation of the surface of a 3D

spherical or ellipsoidal body on a 2D planar map

• Who has used – Google Earth? – Microsoft Visual Earth? – NASA WorldWind?– Another?

27

Yes

28

29

3D worlds

• Great circle - path of minimum distance on surface of sphere, intersection of sphere with plane passing through center of sphere, radius is that of sphere

• Small circle - intersection of any plane with surface of sphere, has radius equal to or less than radius of sphere

• Map projections (reading):– Always have distortions– User chooses which characteristics to

be correct– Distortions depend on scale 30

Properties** to conserve• Area – coin covers the same area anywhere

on map (equal area, equivalent, homolographic, authalic, equiareal)

• Shape – relative local angles are correct (conformal, orthomorphic)

• Scale – no projection conserves scale throughout, equidistant projections give true distances from one point to all others

• Direction – azimuthal projection conserves direction from center of map to all other points

31

Projections

32

33

Other projections• Mercator – lines of constant direction are

straight

• Gnomonic – great circles are straight lines

• Stereographic – great/small circles are circles

34

Types of projections• Cylindrical, conical, planar – can be transformed

(unwrapped) to plane without distortion– Conical – meridians radiate from point, parallels are

circles– Cylindrical – meridians, parallels are straight lines (eg

Mercator)– Planar – meridians radiate from point as straight lines,

parallels are circles

35

Types of projections• Parallels – lines of equal latitude; intersection of

Earth’s surface with planes that parallel the equator; form small circles

• Meridians – lines of equal longitude; planes intersect N and S poles, perpendicular to equator, these are great circles at equally spaced angles, that get close together as one approaches poles

• Oblique projections – cylinder that is not parallel to earth’s axis, cone does not intersect earth’s axis, plane not perpendicular to earth’s axis, results in distortions of parallels and meridians

36

Distances on the Earth• At equator only, 1° latitude = 1° longitude.

• For sphere (or circle) the total circumference = 2 pi R (pi = 3.1415926…, R = radius)

37

For arc of angle a the arc length is aR.

(a is always in radians, for sphere a = 2 pi )R for Earth = 6370 km so a = 1° = 111.19 km.

References for Coordinates• Equator – latitude = 0, positive northward,

negative southward

• Prime meridian (Greenwich UK) longitude = 0, positive eastward, negative westward

• Grids, often made of lon-lat

• Cartesian coordinate systems, usually local, designate points by perpendicular distances from axes on a flat map

• Y – meridians, positive North (northings)

• X – parallels, positive East (eastings) 38

United States• In US we use UTM (Universal Transverse

Mercator) and SPCS (State Plane Coordinate Systems)

39Large regions are divided into zones to decrease distortion.

Oblate spheroid

40

Earth is flattened by about f » 1/300f = (a-b)/a » 1/300 » 22 / 6370 km; a – b » 22 km

Earth’s flattening is sufficient to distort maps at 1:100,000 and larger scales.

In reality – it’s a Geoid• Earth is not an exact ellipsoid and its real shape is

called the geoid. The geoid is the shape the Earth’s surface would have if it was entirely covered with water, in other words, sea level defines the geoid and is an equipotential surface. Local variations in the gravity field cause the geoid to stray from the ellipsoid by ~ ± 100 meters in height.

• The geoid is important in surveying because it locally defines vertical (by gravity). Elevations estimated by traditional leveling are relative to the geoid and not to the ellipsoid. Elevations estimated by GPS are relative to the ellipsoid.

41

Reference ellipsoid • Reference ellipsoid requires 2 constants be

specified; (1) a and b, (2) a and f, or (3) a and e (e = eccentricity).

• There are many different global datums in use today. Satellite-based reference systems e.g. GRS80 and they largely differ in shape of Earth used.

• NB. a datum is a reference point or surface against which position measurements are made, and an associated model

• Global a and f may be inaccurate for local or even continental scale surveying. Local values used to increase local accuracy.

42

Reference ellipsoid • NAD83 (and 27, the North America Datum)

terrestrial and space-based WGS84 (and 72, 64 and 60 of the World Geodetic System) is being replaced by GPS-based reference system

• Perhaps even a ‘moving’ reference frame like ITRF96 (International Terrestrial Reference Frame) in which points are given initial positions and velocities

• OSGB36 of the Ordnance Survey of Great Britain• ED50, the European Datum• Australians, everyone…

43

Latitude for an ellipsoid• A = geographic (geodetic) latitude,

• B = geocentric latitude

• A is slightly greater than B, at poles and (recall) equator A = B

44

Huh? Geodetic/geocentric?• It is important to note that geodetic latitude is

different from geocentric latitude.

• Geodetic latitude is determined by the angle between the normal of the spheroid and the plane of the equator, whereas geocentric latitude is determined around the center

45

Summary• GIS relies on basic elements (review)

• Information and Science

• Having seen this simple introduction be thinking of how to use GIS for Science, i.e.– What exists at a certain location?– Where are certain conditions satisfied?– What has changed in a place over time?– What spatial patterns exist?– What if this condition occurred at this place? (modelling, hypothesis

testing)

– (from Dawn Wright, OSU/GIS465) 46

Reading for this week• GPS

• Map projections

• Georeference systems

• MapInfo User Guide and other docs

• We will discuss (and install, work with) these on Friday (3rd)

47

Next classes• Fri class was to be install MapInfo / Map Basic• Start working with it, ask questions…• In preparation – see the notes that Max put together

(under reading)

48