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- 1. Data Models Introduction to GIS – Spring 2013 1 M. Corbalis
- 2. Data Models • Geographic Information Systems use an abstraction of reality. • We create models – sets of constructs for describing and representing selected aspects of the real world in a computer. • Models are composed of a mix of raster, vector, and attribute data. (rules too.) • Model is tailored to a specific function. Introduction to GIS – Spring 2013 2 M. Corbalis
- 3. Coding Vector Data node node B C Polygon I Polygon node III Polygon A II node node F D Polygon V Polygon IV node G Reality Vector Model Introduction to GIS – Spring 2013 3 M. Corbalis
- 4. Coding Vector Data node node B C Polygon I Polygon III node A Polygon II node node E F node D Polygon V Polygon IV node G Introduction to GIS – Spring 2013 4 M. Corbalis
- 5. Topologic Vector Model node node B C Polygon I Polygon III node A Polygon II node node E F node D Polygon VA topologic vector model records the points and lines Polygon IVshared between polygons as unique items – so, every one node Gof the points and lines are recorded in the data only once Introduction to GIS – Spring 2013 5 M. Corbalis
- 6. Topologic Vector Model node node B C node A Polygon II node E node DPolygon II is on the right sideof the line ABCED. Introduction to GIS – Spring 2013 6 M. Corbalis
- 7. Topologic Vector Model Polygon 2 “knows” it’s adjacent to Polygons 1, 3, & 4. It shares a line segment with each. Polygon I Polygon node III A Polygon II node node E F node D Polygon V Polygon IV Polygon 2 “knows” it touches Polygon 5. It shares node E with Polygon 5. Introduction to GIS – Spring 2013 7 M. Corbalis
- 8. What is Topology? • Shared Geometries, Adjacency and Overlap • Where points, lines, and polygons share individual vertices. Move a point and it moves a vertex in a line/polygon, and vice versa. • Two polygons that share vertices are considered adjacent. • Overlapping (or non-overlapping) features can be located, and then marked as errors. Introduction to GIS – Spring 2013 8 M. Corbalis
- 9. Strict Topology node node• Features are composed B C from a common set of Polygon points and lines. I Polygon node III• Altering the vertices of A Polygon II node node one polygon affects E node F polygons that share D Polygon those vertices. Polygon V IV• Harder to introduce node G gaps or slivers. Introduction to GIS – Spring 2013 9 M. Corbalis
- 10. Topology?• Reasons topology would be important to model?• Where in the real world is this concept important? Introduction to GIS – Spring 2013 10 M. Corbalis
- 11. Cadastre Example benchmark survey (COGO) parcels zones Introduction to GIS – Spring 2013 11 M. Corbalis
- 12. Topology Applied : Parcel Overlap• The boundaries of two properties should never overlap, and there should never be a gap between them, unless intentional.• Clear error in parcel boundaries. Introduction to GIS – Spring 2013 12 M. Corbalis
- 13. Policy-based Topology Rules• In the NJ State Plan, CESs and the Environmentally Sensitive Planning Area both represent areas of environmental importance. – CESs should never be placed on top of the ES Planning Area.• In our utility network, poles hold up the transmission lines. – The transmission line features must always share a vertex with the utility pole point features. Introduction to GIS – Spring 2013 13 M. Corbalis
- 14. GIS is Extensible• With modern GIS, a polygon is not just a polygon.• Software can be adapted to fit your model of reality.• The software can be easily extended to create new data types and perform new analyses.• GIS can be adapted to store, model, and display data about any observable phenomenon on the Earth. Introduction to GIS – Spring 2013 14 M. Corbalis
- 15. Objects• GIS Features as Objects is a recent method of representing aspects of the real-world in GIS• Example of the shift from specialty data to DBMS that are spatially-aware• Non-planar, temporally shifting, topologically linked, rule-based actions• Still important to check for topology to ensure as a quality control step Introduction to GIS – Spring 2013 15 M. Corbalis
- 16. Vector Geometry as Objects• Parcels – Planar geometries with attribute information• Parcels as objects in a Cadastral “carpet” – Objects with topology rules (“don’t overlap, unless”) – Members of “regional” features (zoning, municipality) – Composed of surveyed parts (COGO, benchmarks) – Keys that link to attribute tables (owner(s), assessments, plans, etc) Introduction to GIS – Spring 2013 16 M. Corbalis
- 17. Attributes as Objects• Not only can multiple sets of geospatial features interact with rules, the attributes can be linked with one another, with their own set of rules and actions• Ownership record linked to GIS parcel – Search on multiple owners, records – Removal of parcel warns about “orphan” owner• Functions that can be performed by GIS analyst can be embedded in the actual database Introduction to GIS – Spring 2013 17 M. Corbalis
- 18. Exploring Models• Let’s take a look at several GIS data models.• Take note of the storage method: – Raster – Vector (and vector type: point, line, polygon, etc…)• Also take note of the model family: – Topological Model – Object Model – Both Introduction to GIS – Spring 2013 18 M. Corbalis
- 19. Elevation using LIDAR• LIDAR data is 3D elevation data recorded from an airplane.• Stored as “mass points” – even a small area is composed of thousands of point features.• No real need for attributes, simply XYZ points.• Points can be joined together to create a surface model of a landscape. Introduction to GIS – Spring 2013 19 M. Corbalis
- 20. Elevation DEMs• Digital Elevation Models, or DEMs, often refer to a raster representation of elevation.• Each cell in the raster grid contains a value that is the height of the cell above a fixed point (i.e. sea level). Introduction to GIS – Spring 2013 20 M. Corbalis
- 21. Elevation using TINs • Triangulated Irregular Networks, or TINs are vector models that represent elevation. • The study area is composed of individual triangles, composed of a network of shared nodes and edges • The surfaces of the triangles attempt to represent the surface, so in areas of gradual elevation change, there are fewer triangles. Introduction to GIS – Spring 2013 21 M. Corbalis
- 22. TIN Model of Campus Introduction to GIS – Spring 2013 22 M. Corbalis
- 23. TIN Model of Campus Introduction to GIS – Spring 2013 23 M. Corbalis
- 24. Networks• Analysis can be performed across a network, represented by a feature dataset of points and lines.• Road network or water, sewer, utility, rail, etc…• Optimal route – shortest, lowest cost, avoiding left turns, follow height and weight restrictions, time of day restrictions, include real-time traffic…• Multi-modal – walk/bike to bus stop, bus to train, walk from train to final destination. Introduction to GIS – Spring 2013 24 M. Corbalis
- 25. Networks Introduction to GIS – Spring 2013 25 M. Corbalis
- 26. Networks Introduction to GIS – Spring 2013 26 M. Corbalis
- 27. Models Diagrammed• GIS models can be depicted in a schematic form, similar to a flow chart.• Shows the interconnected nature of the classes that make up the overall model.• Some models can be constructed within ArcGIS using ModelBuilder. Introduction to GIS – Spring 2013 27 M. Corbalis
- 28. Models Diagrammed Introduction to GIS – Spring 2013 28 M. Corbalis
- 29. NJ DEP Wastewater Model Introduction to GIS – Spring 2013 29 M. Corbalis
- 30. NJ DEP Wastewater Model Environmental Science Data Modeling Other Discipline Specific Data Models Introduction to GIS – Spring 2013 30 M. Corbalis
- 31. Creating GIS Models• Abstractions of reality naturally have shortcomings.• Models tailored to a specific task can be used to explore phenomenon or predict effects.• Developing a data model to solve a problem is how GIS has become a decision-making platform.• Consider how you could study an abstract set of data using GIS to solve real-world issues. Introduction to GIS – Spring 2013 31 M. Corbalis
- 32. Raster Introduction to GIS – Spring 2013 32 M. Corbalis

Full NameComment goes here.Panha Hok, Student at Pour un Sourire d'Enfant - Cambodia 1 month ago