GIS_Data_models.ppt Dr. Rapanwad Sunil Ramrao

GIS_Data_models.ppt

1. Dr. Rapanwad S. R.Dr. Rapanwad S. R.

2. GIS Data ModelsGIS Data Models
Vector Data ModelsVector Data Models
Vector File FormatsVector File Formats
Raster Data ModelsRaster Data Models
Raster File FormatsRaster File Formats
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

3. Data AbstractionData Abstraction
•To use GIS the real world must be
abstracted into points, lines, polygons,
raster cells, and attribute values
•Class examples may use common object
that most people will understand. If you
understand how to abstract common
objects you will be able to apply the same
method to object in your field
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

4. What is Vector DataWhat is Vector Data
•Vector Data uses Points and their (X,Y)
coordinates to represent spatial features
•Points, Lines and Polygons
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

5. PointsPoints
•A point is a 0 dimensional object and has
only the property of location (x,y)
•Points can be used to Model features such
as a well, building, power, pole, sample
location ect.
•Other name for a point are vertex, node, 0-
cell
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

6. LinesLines
•A line is a one-dimensional object that has the
property of length
•Lines can be used to represent road, streams,
faults, dikes, maker beds, boundary, contacts
etc.
•Lines are also called an edge, link, chain, arc, 1-
cell
•In an ArcInfo coverage an arc starts with a node,
has zero or more vertices, and ends with a node
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

7. Figure 4.3 p58 BernhardsenFigure 4.3 p58 Bernhardsen
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

8. PolygonsPolygons
•A polygon is a two-dimensional object with
properties of area and perimeter
•A polygon can represent a city, geologic
formation, dike, lake, river, ect.
•Other name for polygons face, zone 2-cell
•Scale matters
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

9. Dr. Rapanwad S. R.Dr. Rapanwad S. R.

10. Data Abstraction DiscussionData Abstraction Discussion
•If you do not understand this the rest of
GIS will not make sense
•Scale Matters
•Intended use Matters
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

11. ExamplesExamples
•Trees
•Dikes
•Roads
•Rivers
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

12. TopologyTopology
•A set of rules on how objects relate to
each other
•Major difference in file formats
•Higher level objects have special topology
rules
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

13. Topology DefinitionTopology Definition
•The Science of mathematics of relationships
used to validate the geometry of vector entities,
and for operations such as network tracing and
tests of polygon adjacency.
•The study of geometric properties that do not
change when the forms are bent, stretched or
under go similar geometric transformations.
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

14. Figure 2-9 GIS Fundamentals, Bolstad
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

15. Planar EnforcementPlanar Enforcement
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

16. Why Topology MattersWhy Topology Matters
•Error Detection
open polygons
unlabeled polygons
slivers
polygons that cannot exist next to each
other
•Network Modeling
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

17. Show PlacitasShow Placitas
•Arc Node Topology
–Cover#
–Lpoly# and Rpoly#
–Tnode fnode
•Label errors
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

18. Higher Level ObjectHigher Level Object
•Regions
•Networks
•TIN – Triangulated irregular network
•Dynamic Segmentation
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

19. RegionsRegions
Overlapping areas with different attributes
e.g.Fire history
Disconnected areas with the same attributes
e.g. Hawaii
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

20. NetworksNetworks
•Road systems, power grids, water supply
sewerage systems, drainage network
•Continuous connected networks
•Rules for displacement in a network
•Attribute value accumulations due to
displacements
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

21. TINTIN
•Vector Surface Model
•Triangulated Irregular Network
•A set of nonoverlapping triangles each
with a constant gradient
•A TIN can honor original input elevations
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

22. Dynamic SegmentationDynamic Segmentation
•Combines a line coverage with a linear
reference system
•Has event tables for point events and
linear events
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

23. Fig 3.13 p52 ChangFig 3.13 p52 Chang
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24. Examples and DemoExamples and Demo
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

25. Shape FilesShape Files
•Nontopological
•Advantages no overhead to process
topology
•Disadvantages polygons are double
digitized, no topologic data checking
•3 files .shp .shx .dbf
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

26. CoveragesCoverages
•Original ArcInfo Format
•Directory With Several Files
•Database Files are stored in the Info
Directory
•Uses Arc Node Topology
–Planer Enforcement
–Connectivity
–Adjacency
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

27. GeoDatabaseGeoDatabase
•New GIS Format at ArcGIS 8.0
•Two Types
–Personal Geodatabase
–Microsoft access 2000 database
–SDE GeoDatabase
–Multi-user
–Can connect to many RDBMS
•Oracle, SQL server, Informix
•File are stored in the format native to the RDBMS
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

28. Box 3.5 Geographic Information Box 3.5 Geographic Information
Systems, Chang 04 p. 55Systems, Chang 04 p. 55
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

29. GeoDatabaseGeoDatabase
•Shapes are similar to shape files
•Object-oriented model not a Geo-relational
•There are 25 topology rules that can be
used to relate different layers
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

30. Raster Data ModelRaster Data Model
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

31. Figure 3:1 Getting Started with Figure 3:1 Getting Started with
Geographic Information Systems, Geographic Information Systems,
Clarke (2003) p. 91Clarke (2003) p. 91
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

32. Grid PropertiesGrid Properties
•Each Grid Cell holds one value even if it is empty.
•A cell can hold an index standing for an attribute.
•Cell resolution is given as its size on the ground.
•Point and Lines move to the center of the cell.
•Minimum line width is one cell.
•Rasters are easy to read and write, and easy to
draw on the screen.
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

33. Dr. Rapanwad S. R.Dr. Rapanwad S. R.

34. Dr. Rapanwad S. R.Dr. Rapanwad S. R.

35. Raster PyramidsRaster Pyramids
•With out pyramids the entire raster must
be read for each screen draw
•Pyramids store reduced resolution dataset
files .rrd to increase the speed of screen
draws
•When you add a raster to ArcMap if
pyramids do not exist you can create them
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

36. Raster ResamplingRaster Resampling
•Nearest Neighbor
–Closest cell
–Continuous and Discrete data
•Bilinear interpolation
–Average of nearest 4 cells
–Continuous data only
•Cubic Convolution
–Average of nearest 16 cells
–Continuous data only
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

37. Quad Tree CompressionQuad Tree Compression
•May be use to get variable resolution for
imagery in the National Map
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

38. Figure 4.35 Geographic Information Systems and Introduction,
Bernhardsen (2001), p. 87
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

39. C. Dana Tomlin, Geographic Information Systems and Cartographic C. Dana Tomlin, Geographic Information Systems and Cartographic
Modeling (1990), P. 44Modeling (1990), P. 44
•“Yes raster is faster, but raster is vaster,
and vector just seems more corrector”
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

40. Images are a form of raster dataImages are a form of raster data
•ArcGIS can use many common image
formats
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

41. Dr. Rapanwad S. R.Dr. Rapanwad S. R.

42. Dr. Rapanwad S. R.Dr. Rapanwad S. R.

43. Dr. Rapanwad S. R.Dr. Rapanwad S. R.

44. Dr. Rapanwad S. R.Dr. Rapanwad S. R.

45. Industry Standard Data ModelsIndustry Standard Data Models
•Some Industries have created standard
data models
•It is a good idea to use a standard model
to promote sharing of data
•Some data models can be very complex
•Complex models require custom tools to
be useful
Dr. Rapanwad S. R.Dr. Rapanwad S. R.

46. Dr. Rapanwad S. R.Dr. Rapanwad S. R.

47. ReferencesReferences
•Getting Started with Geographic Information
Systems 4
th
Edition, Clark (2003)
•Geographic Information Systems an Introduction
3
rd
Edition, Bernhardsen (2002)
•Introduction to Geographic Information Systems
2
nd
Edition, Chang (2004)
•GIS Fundamentals, Bolstad (2002)
•ArcGIS 8.3 Desktop Help
•Using GRID with ArcInfo version 7 ESRI
Dr. Rapanwad S. R.Dr. Rapanwad S. R.