Presentation on theme: "Created by Lisa Bingham University of Stavanger, Norway"— Presentation transcript:
1Created by Lisa Bingham University of Stavanger, Norway Maps and GISCreated by Lisa BinghamUniversity of Stavanger, NorwayLisa BinghamContact for questions, list of readings used in course, and labs or other assignments.Course originally planned for a 12-week Bachelor of Science degree in Petroleum Geoscience Engineering
2Course Objectives Read, understand, and interpret maps Basic understanding of GISBasic understanding of GPS
5Reading maps Maps relate information Investigate the map It is up to the viewer to interpret the informationHow?Investigate the mapIdentify the parts of the mapFamiliarize yourself with the mapAre there graphs? Inset maps? Additional figures?What is the purpose of the map? What does the map tell you? What information does it relate?
6What makes a “good” map? Defined purpose and audience. These influence what makes a “good” map for the intended audience.tourist vs. geologistAvoid cluttering or over-complicationsLegible labelingColoring and patterns should follow cartographic conventions.
7Features of a map A concise map title An easy to read scale bar An easy to read legend, if necessaryNorth arrow if the coordinate system is not clear or if the map is turned to an angleLegible coordinates at the border of the mapProjection information
8Identify the parts of a map Locate:TitleScaleScale barLegendCoordinate systemor grid markingsLocation or inset mapPublication information
9publication information Where is the title?TitleWhere is the legend?Where is the inset map?Where is the scale bar?ScaleScalebarWhere is the scale?Where are the grid coordinates?Where is the north arrow?Where is the publication information?Compiler andpublication informationWhere are the graphs?Some maps have north arrows or compass roses, or may include projection information. This map does not.LegendInset mapGridcoordinatesGraphs
11What does the map tell you? Mineral-rich in the northMineral-poor in the centerMinerals in the southWhat does the map tell you?Diamonds with goldin the northeastGold in north-centralIf you represented a mining company,where would you look for:gold?diamonds?bauxite?radioactive minerals?Mica-rich in the southDiamond production decreasing
12Understanding Map Scales Representations:verbal (1 map centimeter represents 30,000 ground centimeters)fraction (1:25,000)graphic (scale bar)Map scale indicates how much a given distance was reduced to be represented on the map.
13Understanding Map Scales Small-scale map depicts large areas, so low resolution.1:10,000,000
14Understanding Map Scales Large-scale map depicts small areas, so high resolution.1:50,0001,267 inches to 1 mile
15Small-scale vs. Large-scale Maps When the scale is written as a fraction, is the fraction very small or very large?1/1,0001/100,0001/1,000,0001/5,000,0001/10,000,000Identifying a map as small- or large-scale is an exercise of relativity
16Reading Map Contours First familiarize yourself with the map Locate the contour intervalInvestigate the contoursAre they close together? Far apart?Are the very straight?Are there many concentric circles?Do the contours shape like V’s or U’s?
19What can be said about the elevation in this area (northeast corner of the previous map)?
20What can be said about the elevation in this area (northeast corner of the previous map)? V shapeSteep slopesCoastlineV shapeLess steep area
21What can be said about the elevation in this area (central area of the large map)?
22Steeper area with very curvy contours High point or depression? What can be said about the elevation in this area (central area of the large map)?Flat areaCoastlineFlat areaSteeper area with very curvy contoursHigh point or depression?
25What is a coordinate system? A mathematical system used to explain the location of a point on the earth (or other planet).A geographic coordinate system is used to assign geographic locations to objects.A global coordinate system of latitude-longitude is one such framework.Another is a planar or Cartesian coordinate system derived from the global framework.
26Latitude facts:Lines of latitude (parallels) are evenly spaced from 0o at equator to 90o at poles.60 nautical miles (~ 110 km)/1o, ~1.8 km/minute and ~ 30 m/second of latitude.N. latitudes are positive, S. latitudes are negative.EquatorFrom M. Helper, University of Texas, 2008
27Longitude facts:Lines of longitude (meridians) converge at the poles; the distance of a degree of longitude varies with latitude.Zero longitude is the Prime (Greenwich) Meridian (PM); longitude is measured from 0-180o east and west of the PM.East longitudes are positive, West longitudes are negative.P.M.180oFrom M. Helper, University of Texas, 2008
28Units of Measure Decimal degrees (DD), e.g. - 90.50o, 35.40o order by longitude, then latitudeFormat used by ArcGIS softwareDegrees, Minutes, Seconds (DMS), e.g. – 90o 30’ 00”, 35o 24’ 00”From M. Helper, University of Texas, 2008
29What is a map projection? A map projection is used to portray all or part of the round Earth on a flat surface. This cannot be done without some distortion.Every projection has its own set of advantages and disadvantages. There is no "best" projection.The mapmaker must select the one best suited to the needs, reducing distortion of the most important features.
30Laying the earth flat Why? Need convenient means of measuring and comparing distances, directions, areas, shapes.Traditional surveying instruments measure in meters or feet, not degrees of longitude and latitude.Globes are bulky and can’t show detail.1:24,000 globe would have diameter of ~ 13 mTypical globe has scale of ~ 1:42,000,000Distance & area computations more complex on a sphere.From M. Helper, University of Texas, 2008
31Laying the earth flat How? Using projections – transformation of curved earth to a flat map; systematic rendering of the longitude and latitude graticule to rectangular coordinate system.Scale 1: 42,000,000Scale Factor(for specific points)MapEarthGlobeGlobe distance Earth distanceMap distance Globe distanceMercator ProjectionFrom M. Helper, University of Texas, 2008
32Inflatable globe demonstration Blown upandCut upUse a beach ball globe to demonstrate the flattening of a globe. Start with a blown up beach ball. Let the students investigate. Then show a cut up beach ball. You could if you have the resources, cut the ball in front of the students.
33Laying the earth flatSystematic rendering of Latitude (f) & Longitude (l) to rectangular (x, y) coordinates:y0, 0xGeographic Coordinates (f, l)Projected Coordinates (x, y)Map ProjectionFrom M. Helper, University of Texas, 2008
34Laying the earth flat “Geographic” display – no projection x = l, y = fGrid lines have same scale and spacinglfyxFrom M. Helper, University of Texas, 2008
35“Geographic” DisplayDistance and areas distorted by varying amounts (scale not true); e.g. high latitudeslfyxFrom M. Helper, University of Texas, 2008
36Projected Display E.g. Mercator projection: f x = l 905+E.g. Mercator projection:x = ly = ln [tan f + sec f]yFrom M. Helper, University of Texas, 2008
37Laying the earth flat How? Projection types: Orthographic Gnomonic StereographicaA’A’A’aaT’T’T’TTTbB’B’bbB’From M. Helper, University of Texas, 2008
38Inflatable globe demonstration Light shines throughUse a beach ball that has the top cut out. Dangle a light bulb inside and outside.
39Projection produces distortion of: DistanceAreaAngleShapeDistortions vary with scale; minute for large-scale maps (e.g. 1:24,000), gross for small-scale maps (e.g. 1: 5,000,000)Goal: find a projection that minimizes distortion of property of interestFrom M. Helper, University of Texas, 2008
40How do I select a projection? Scale is critical – projection type makes very little difference at large scalesFor large regions or continents consider:Latitude of areaLow latitudes – normal cylindricalMiddle latitudes – conical projectionHigh latitudes – normal azimuthalExtentBroad E-W area (e.g. US) – conicalBroad N-S area (e.g. S. America) – transverse cylindricalThemee.g. Equal area vs. conformal (scale same in all directions)From M. Helper, University of Texas, 2008
41How to know which map projection to use? General guide:Conventions for different areas or fields of study
43Key Questions and Issues What is GIS?What are the applications of GIS?How is the real world represented in GIS?What analyses can GIS perform?
44What does GIS stand for?GIS is an acronym for “Geographic Information System”
45What is GIS?Computerized management and analysis of geographic informationGroup of tools (and people) for collection, management, storage, analysis, display and distribution of spatial data and informationComputer-based tool for mapping and analyzing things that exist and events that happenRefer to readings for other definitionsFrom M. Helper, University of Texas, 2008
46GIS SoftwareThere are several GIS software programs available for use.Open source (not necessarily free)MapServerTerraViewQuantum GISUDigProprietary softwareIDRISIGMTManifoldMapPointESRI (used in class)
47GIS ExampleFrom M. Helper, University of Texas, 2008
48A GIS is Composed of Layers GeologyDEMDigital elevation modelHydrographyRoadsFrom M. Helper, University of Texas, 2008
49Features have locations StavangerX = mY = mX axisOrigin (0, 0)Y axisFrom M. Helper, University of Texas, 2008
50Spatial relationships can be queried What crosses what?Proximity – What is within a certain distance of what?Containment - What’s inside of what?Which features share common attributes?Many othersFrom M. Helper, University of Texas, 2008
51Remember GIS focuses on geographic information If something has a location or is associated with a location, it can be mapped.
52Key Questions and Issues What is GIS?What are the applications of GIS?How is the real world represented in GIS?What analyses can GIS perform?
53The Global Positioning System From M. Helper, University of Texas, 2008
54GPS Facts of Note Today ~30 satellites for GPS USA Department of Defense navigation systemFirst launch on 22 Feb 1978Originally 24 satellitesToday ~30 satellites for GPSFrom M. Helper, University of Texas, 2008
55GPS Milestones 1978: First satellites launched 1983: GPS declassified 1989: First hand-held receiver1991: S/A activated (large error in location)1993: GPS constellation fully operational: First hand-held, “mapping-grade” receivers: GPS on a microchip1997: First $100 hand-held receiver2000: S/A off (more accuracy)GPS – Milestones1978: First 4 satellites launched1983: GPS declassified - Korean airliner shot down over Soviet airspace - first civilian receivers: Challenger Disaster hiatus1989: First hand-held receivers – Magellan1991: S/A activated; DGPS becomes essential for surveying and mapping1993: I buy my first GPS receiver – Trimble Scout1993: GPS constellation full operational status (24 SVs; 5-8 visible anywhere, anytime): First hand-held, “mapping-grade” receivers (DGPS capable, data dictionary).: GPS on a chip developed –receivers can use external CPUs1997: First hand-held receivers for under $1002000: integration of GPS and cellular technology2000: SA is turned off; inexpensive GPS receivers horizontal accuracy increased from ~ 100 meters to meters – detailed mapping with a single receiver possible2003: FAA commissions WAAS – Free wide-area DGPS - properly equipped receiver can obtain horizontal precision of m, vertical precision of 7 m. “Survey-grade” equipment no longer needed for all but most precise work.From M. Helper, University of Texas, 2008
56GPS Segments Space – Satellites (SVs). Control – Ground stations track SV orbits and monitor clocks, then update this info for each SV, to be broadcast to users.User – GPS receivers convert SV signals into position, velocity and time estimates.From M. Helper, University of Texas, 2008
57How are SV and receiver clocks synchronized? Clock errors will cause spheres of position (solid lines) to miss intersecting at a point.Adjust receiver clock slightly forward will cause larger DT(=larger sphere; dashed) and intersection at point.Requires 4 SVs, not 3 as shown, for clock error & X, Y, ZFrom M. Helper, University of Texas, 2008
58Satellite Positioning Observe DTOrbitKnownDetermineGeocenterFrom M. Helper, University of Texas, 2008
593-D (X, Y, Z) One-way Ranging Intersection of 2 spheres of position yields circleIntersection of 3 spheres of position yields 2 points of locationOne point is position, other is either in space or within earth’s interiorWith earth ellipsoid (4th sphere)Get receiver clock synchronized and X & Y but no ZIntersection of 4 spheres of position yields XYZ and clock synchronizationFrom M. Helper, University of Texas, 2008
60Tropospheric Delay (~ 0.5 m) Sources of ErrorSatellite Orbit Errors (~2.5 m)SV clock error (~1.5 m)L2L150 kmIonospheric Refraction (~ 5 m) (Can correct with L1 & L2 DTs)200 kmTropospheric Delay (~ 0.5 m)Multipathing (~0.5 m)+ GDOP (errors x 4-6)(Geometric dilution of precision)From M. Helper, University of Texas, 2008
61Satellite Constellation Must have a good spread of satellites
62GPS Resolution and Map Scales From M. Helper, University of Texas, 2008
63Familiarization with GIS Software used is ESRI ArcGIS, but concepts are the same with any GIS software program.
65Vector dataAn x, y coordinate system references the real-world location.Shapefiles and feature classes (file types) are vector data.Appropriate for discrete data where boundaries are needed.Pipeline location.
68Raster dataRaster data may be a georeferenced jpg or tiff, or a converted ASCII grid.Appropriate for continuous data where discrete boundaries are not necessary.TopographyGrid filesCells contain Z data.The smaller a cell size, the higher the resolution.
69Practical uses of raster data Simple display of a rasterTopography (elevation)Bathymetry (depth)GravityMagnetic anomalies
70Advanced uses of raster data Additional processing of rasterChanges in morphologySediment thicknessHill shades (Creating texture)ContoursTopographic profilesSpatial analysisMap algebra
71Using Satellite Data with GIS OmanGPS DataDatapointsTracksRemote Sensing DataSatellite imagesRADARBeijing, China
72Using Satellite Data with GIS Digitize buildings and roadsDigitize faults, scarps, rivers, or elevationBeijing, ChinaOman
74Acquiring External Data Government and non-government agencies may provide free GIS dataQualityMap purpose influences acceptable quality
75General Websites: Shapefiles Norwegian Petroleum DirectorateGIS Data Depot data.geocomm.comDIVA-GISNorwegian Geological Survey (NGU)United States Geological SurveyMany others
76General Websites: X,Y Data (Need Converting) USGS NEIC Earthquake Database
77General Websites: Grids (May Need Converting) General Bathymetric Chart of the Oceans (GEBCO)CGIAR-CSI SRTM Processed NASA satellite topography dataScripps Institution of OceanographyNGDC World Magnetic Anomaly Map
78General Websites: Maps (Need georeferencing) The University of Texas at Austin Perry-Castañeda Library Map CollectionGoogle Image search
79Identify featuresSelect the identify tool.Click on a feature.
80Why select features? Create subsets Find data Find counts of data with certain attributesFind data near a location
81Select by attributes Use Select by Attributes wizard Use when attribute values are known and assignedCan be unique
82Select by location Use select by Location wizard Location with buffers What is a buffer?Location with respect to another dataset
83Creating and editing shapefiles Not all data that is needed for a mapping project will be available in GIS formatSome data is extremely expensive to buySome data is not available for purchaseSometimes the GIS technician needs to create new data based on other map layers
85What is Georeferencing? It is a process by which locational information (geo) is added (reference) to an image (raster) in a GIS program.A point on the image is assigned a coordinate pair in two ways:By lining up the image to a featureBy adding coordinates directly
86For Example:Align raster image to vector data (shapefile or feature)
87Nature of the problem: Data source registration may differ by: RotationTranslationDistortionTranslationRotationDifferential ScalingSkewDistortionFrom M. Helper, University of Texas, 2008
88General problem is then: Control Points“Displacement Link”(0,1)(1,1)(501000, )(0,0)(1,0)(498100, )Source (x, y)Destination (X’, Y’)(“Warp”)From M. Helper, University of Texas, 2008
89What images to use? Trusted sources (published maps from map agencies) Clear coordinate system markings (Decimal degrees for Geographic Coordinate Systems; Meters for UTM and Mercator, but need a reasonable guess of UTM zone or Mercator)Clear country boundaries, city locations, major roads, major rivers
90What images to discard?Sketchy sources (personal websites or unpublished sources)Blurry, coarse or very thick country boundaries. These are usually over-generalized.Maps that rely on other maps to show their locations (over-use of inset maps)Exceptions: Very old maps which are not available in an updated form!
91Digitizing from Georeferenced Image Obtain information that has not been published in GISObscure publication or out-of-print publicationError margin depends on overall scale of data (global vs continental vs regional vs country/state vs town)