Types of Topological Models: Basic Topological Model, GBF Model, TIGER Model, and POLYVRT Model (Especially for GATE-Geospatial 2022)

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Topological models are further divided into other methods:

  • Basic Topological Model
  • GBF/DIME Model
  • TIGER Model
  • POLYVRT Model
This Diagram Shows Topological Model Methods

1. Basic Topological Model

Topological model is like spaghetti model with additional analysis facility. Spaghetti model is not offering ease of analysis while topological model includes it. To allow advanced analytical techniques to be performed easily, explicit spatial information is needed. For example- each line segment, the basic logical entity in topological data strictures, begins and ends when it either contacts or intersects another line or when a change in direction of the line occurs. For example, an area or polygon is defined by a set of lines which makes up its boundaries. In this case the line is the border between two polygons. Each line then has two sets of numbers:

  • Pair of coordinates
  • Associated node number

Here, node is intersection of two or more lines, and its number is used to refer to any line to which it is connected.

This Diagram Shows Bassic Topological Model

2. GBF/DIME Model

The best-know model is “GBF/DIME” – Geographical Base File/Dual Independent Map Encoding. GBF/DIME model is created by U. S. Bureau of the Census to automate the storage of street map data. In this case, the straight-line segments represent streets, rivers, another line, etc. In this model, each segment ends when it either changes direction or intersects another line. In addition to the basic topological model, the GBF/DIME model assigns a directional code in the form of from node and to node. This approach makes it easy to check for missing nodes.

3. TIGER Model

Some of the problems associated with GBF/DIME system been eliminated with the development of another system known as “TIGER” - Topologically Integrated Geographic Encoding and Referencing System. In this system, points, lines, and areas are explicitly addressed.

Usage

  • Digitally storing street maps
  • Providing geographically referenced address information in computerized form
This Diagram Shows Example of TIGER Model

4. POLYVRT Model

POLYVRT (POLYgon conVeRTer) was developed by Peucker and Chrisman in 1975. This model eliminates the storage and search inefficiencies of the topological model by separately storing each type of entity. These separate objects are then linked in a hierarchical data structure with points relating to lines, which in turn are related to polygons, by using pointer. Explicitly and separately storing each type of POLYVRT data entity in a hierarchical data structure:

  • A chain is denoted as the basic line entity comprised from a sequence of straight-line segments
  • A line segment begins and ends at a node
  • A node is defined as the intersection point between two chains and its position is indicated by x, y coordinates
This Diagram Shows POLYVRT Model

Developed by: