Building Gis World

8/13/2019 Building Gis World

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By,

J. Anne Golda,

13PRGE02



BUILDING GIS WORLD

consider some of the fundamental methods used to

construct computer based GIS worlds by grouping theentities together.

There are, in general, four options to build or construct

GIS real world model.



Types of models

LCGU based GIS

Layer based GIS

Feature based GIS and

Object oriented GIS.



1) LCGU based GIS

The least common geographical units ( LCGU )

also known as Integrated Terrain Units ( ITU )integrate all pertinent spatial data records into a singleset of all classes. .

The integrated terrain units are a combination of

geomorphology, geology, and vegetation complexes(all of which are included as attributes).



2) Layer based GIS The layering approach allows users to visualise a map

database as a set of registered map separations.

Each layer is thematic and reflects either a particularuse or a characteristic of the land use.

The concept of breaking the real world into a series ofthematic layers is the process that is used to developthe first map overlay analysis.



The logical extension of the layer concept is the use oftiles. This approach breaks down geographical spaceinto a series of regular or irregular units that can bereassembled through the use of a coordinate system.

In this model, GIS requires that data are broken down

into a set of logical terrain units to assist with physicaldisplay of data.



3) Feature based GIS

This is a new approach having the trappings of Object

oriented GIS, spatial analysis functionality from rastermodels and power from vector models.



4) Object oriented GIS

This is a relatively new approach compared to

structuring geographical space views of the real worldas a set of individual objects and groups of objects.

This object-oriented approach integrates individual

geographical entities and attributes into semanticobjects with inheritable properties. This approach isbased on object-oriented programming.



The features are not divided into separate layers but grouped into classes and hierarchies of objects.

The object oriented GIS approach, has thecharacteristic feature of collecting, managing, andmaintaining geographical (size, shape and location),

topological (slope and aspect) and behaviour of objectsas related to one another.



The object orient GIS has particular advantages for

spatial modelling over the layered GIS.

However, it does cause some problems associated withimplementation into a workable GIS.

Building Gis World

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