1. Vector Data Model
Chapter 3

2. Geometric Objects What does the object represent?
Point=0 dimension, property of location
Line=1 dimensional and has the property of length
Area=2 dimensional and has the properties of area and boundary.
Basic unit is the point and it’s coordiantes

3. Line
Line is a series of points.
Node
Vertex
Smooth line
Straight line

4. Area
Defined by lines
Contiguous areas
Isolated
Overlapped
Hole

5. Map Scale Ratio of map distance to ground distance.
1:24,000 is 1 cm = 24,000 centimeters or 240 meters.
More details on 1:24,000 than on 1:100,000
What is the symbology?

6. Topological Data Structure
Point: id, x, y
Line: Arc-node list, Arc-coordinate list
Arc-node list: Arc#, Fnode, Tnode (direction)
Arc-coordinate list: Arc#, x-y coordinates.
Polygon: Left/Right list, Polygon/Arc list
Left/Right list: Arc#, Lpoly, Rpoly
Polygon/Arc list: Polygon#, Arc#

7. Digitization Digitizer Undershoot Overshoot
Build/Clean (create topology)

8. Non-topological Vector Data
Computer Aided Design (CAD)
.dxf or .dgn etc
Shapefile (ArcView
.shp = spatial data (geometry)
.shx = index for the .shp
.dbf = attribute data

9. Higher-Level Objects Triangulated irregular network (TIN)
Delaunay triangulation – iterative process of connecting points with their two nearest neighbors to form triangles as equiangular as possible.
x, y, and z values (derived slope and aspect)
Sample points
Triangle#, number of adjacent, plus points, lines and attribute data

10. Higher-Level Objects Regions Simple lines and areas
Region layers (regions with same attributes) and regions
Overlap and/or disconnected/disjoint
Subclass of polygon coverage.
Region-polygon list: Region#, Polygon#
Region-arc list: Region#, Ring#, Arc#

11. Higher-Level Objects Dynamic Segmentation
Sections: arcs of a line coverage
Routes: collection of selections that represent linear phenomena
Events: attributes connected with dynamic segmentation
Section Table, Route Table, Point Event Table, Linear Event Table (more in ArcView presentation)

12. Object-Oriented Data Model
Structural Aspects of Objects
Grouping: association, aggregation, generalization, instantiation, and specialization
Behavioral Aspects of Objects
Inheritance, encapsulation, polymorphism.

13. Spatial Data Concepts Map scale Spatial resolution (instrumentation)
Spatial data accuracy
Location accuracy
Precision

14. Topology Arc/Info Connectivity: Arcs connect to each other at nodes
Area definition: An area is defined by a series of connected arcs
Contiguity: Arcs have directions and left and right polygons.
Similar to TIGER