GIS is an integrated and operational arrangement of computer hardware and software functioning to facilitate the storage, manipulation and modelling of spatially referenced data and non-spatial data in order to make meaningful and efficient policy, planning and management decisions. (Lakhan, 1985).

Adopting the most advanced GIS software technologies, Titan GIS is a powerful decision support tool for mapping and analysing physical objects through querying and analysing relationships between geographic features distributed over space and time. GIS uses the capabilities of the modern personal computer to measure, compare and describe the contents of its databases. It allows ready access to the raw data and allows aggregation and reclassification for further analysis. Patterns and trends are made apparent as a result of GIS analysis, thus helping planners and managers to make more informed decisions.

Titan GIS is a computerised mapping system
draws the association between attribute data and spatial features on a map. GIS is often called a "smart map", linking the power of a database with the visualization of a map. It is said that a picture is worth a thousand words; that maps store and communicate information much more efficiently than text; and that the human eye and brain are marvellously adapted for rapid analysis of visual presentations. (Goodchild, 1997)

TITAN GIS DATA MODELS
Titan GIS supports a complete range of GIS data models including vector, raster, and digital elevation models.

• VECTOR DATA MODEL
  In the vector data model, the world is represented as a mosaic of interconnecting lines and points that represent the location and boundaries of geographical entities. The vector model gives specific spatial locations explicitly and assumes geographic data is continuous. The perspective of the vector data model is based on the object relationship and topological relationship models.
  
  The Titan object relationship model uses objects to represent real-world geographical data. These objects may be in the form of points, lines, or areas (polygons), each of which stand alone without interacting with one another. The object relationship model associates 'points' as a single set of co-ordinates (X and Y), 'lines' as connected sequences of co-ordinate pairs and 'areas' as sequences of interconnected lines whose first and last co-ordinate points are the same. All point, line and area entities have associated with them a separate file that contains corresponding attributes or characteristics.
  
  The topological relationship model integrates the object relationship model with spatial relationships to express geographic data. Topology identifies the spatial relationship between connecting or adjacent geographic elements (point, line, polygon, etc.). This model supports network and area topological relationships, linking all data models to perform advanced GIS analysis including network and overlay analyses.
  The Titan object relationship model supports the following element types:
  Point: A geographical feature represented by a single co-ordinate otherwise too small to be displayed with a line or polygon. An example of a point feature is a single dot representing a well, building, or telephone pole on a small-scale map.
  Multi-Point: A geographical feature making reference to a series of unattached yet similar points as one particular indexed object. A multipoint, however, has only one record in the spatial database and attribute table of the object theme, such as a set of observation points.
  Line: A geographical feature that is shaped by a series of connecting points, or vertices, with the terminal points referenced as nodes. Objects of this linear nature are too narrow to be depicted with a polygon, yet too large for a point element. Streams and roads are prime examples of a line feature.
  Polyline: A polyline is an extension of a line that has only one record in the spatial database and attribute table of the object theme. The tributary streams of a main stream are examples of a polyline.
  Contour: A contour is a line feature that has length representing a distinct feature but lacks area, such as the contour lines illustrating elevation change in terrain.
  Polygon: A geographical feature that is an enclosed, homogenous area outlining a boundary. Countries, islands, reservoirs and land-use zones are represented as polygon features.
  Annotation: A special character, or label, used to identify or describe a particular geographic entity. An example of an annotation feature is the name of a lake, such as "Pacific Ocean", within the appropriate polygon representing this geographic feature.
  
• RASTER DATA MODEL
  The raster (or grid-cell) data model represents geographical objects with grid-cell structures known as pixels or units. Each unit represents a limited but defined amount of the earth's surface. In using the raster data model, a point is located within the space of a single grid cell. Lines are represented as a series of connected grid cells, and an area is represented by points that are bounded by a closed set of lines. To include attribute data for each object, a code number is assigned to each grid cell representing an attribute such as water.
  
  Continuous surfaces are best represented using the raster model. Attributes of a location in a cell-based system are a function of where the location is relative to a phenomenon that is progressively changing as it moves through space. All cells are identical in the raster method and provide uniformity in representing points, lines, polygons and surfaces, which is particularly important when combining data types.
  
  Titan GIS fully supports the raster data model with the capability to perform both simple and complex grid-cell analyses.
  

TIN DATA MODEL
The Triangulated Irregular Network (TIN) data model is used to create, store, analyse, and display continuous surface information in Titan GIS. TIN is a set of adjacent, non-overlapping triangles computed from irregularly spaced points with X, Y and Z co-ordinates. The TIN data model stores the topological relationship between triangles and their adjacent neighbours. This data structure allows for the efficient generation of surface models for the analysis and display of terrain and other types of surfaces.

TITAN DATA MANAGEMENT
Titan GIS uses a theme (layer) approach to organise spatial information. Each theme is characterised by the features it depicts, its method for representing shape and location, and its appropriateness for performing various geographic operations. Titan GIS supports the following themes:

• Vector Theme: As the vector data model encompasses the object relationship model and the topological relationship model, the vector theme is classified as an object and topology theme.
• Object Theme: In an object theme, features are stored as simple points, multipoints, lines, polylines, contours, polygons and annotations. The locational data for these features is represented explicitly as a series of X, Y co-ordinates. For example, city streets may be represented as a set of lines defined by and stored as sets of x, y coordinates that define each street.
• Topological Theme: Topological themes are used to support vector topological relationships, and are represented as a combination of other features. For example, a city block may be defined by the set of streets that make up its border.
• Grid Theme: Grid themes are represented by raster data. The grid theme can represent areas, points and lines, as well as continuous surfaces. For example, the geographic feature "slope" may be best represented using the grid theme.
• TIN Theme: TIN themes are used to support the TIN data model. For example, the geographic feature "elevation" might best be represented using the TIN theme.
  

TITAN DATABASE MANAGEMENT SYSTEM
A database is simply an electronic card index in which one card, or record, contains a set of information and a reference number to link the card to a particular object. In Titan, each geographic feature is connected to a database through a unique identification number. Titan uses a CodeBase Database Management System (DBMS). A DBMS is a software application used to enter, store, organise, retrieve and query information in a database.

Titan GIS users also have the option to incorporate external database management systems such as Access, Oracle, Sybase, Informix or DB2 to extend Titan's database management capabilities. Communication with external databases is accomplished using an ODBC interface. ODBC is a Microsoft component that enables communication between different database systems. Once connected to an external ODBC database, the Titan user can create database tables or initiate scripts that perform actions on the data in the external database.

• SPATIAL DATABASE TABLES
  Spatial data graphically describes the location and topology of geographic features such as points, lines and polygons. Titan GIS stores spatial data in a spatial database that is managed by the internal database management system.
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  ATTRIBUTE DATABASE TABLES
  Attribute data is the information describing the characteristics of geographic features. Titan uses both Theme Attribute Tables and Related Tables.
  
  Attribute tables are created by Titan GIS software when a new theme is created. For each feature in a theme, there exists one record in the Theme Attribute Table. Theme Attribute Tables contain a mandatory set of attribute items required by Titan GIS. The user has the ability to add feature attributes to the Related Tables to record additional information about a feature. The related tables are necessary because every feature has a corresponding row in the feature attribute database and large amounts of redundancy can occur if attribute data is attached to each record. Related tables can minimise redundancy, help maintain data integrity and result in faster execution of Titan GIS programs

DATA INPUT
For a GIS to analyse the information in a map, the data must be in a digital format that the computer can recognise. Maps can be digitised (hand-traced with a computer mouse) to collect the co-ordinates of the map features. Another way to convert a map into digital form is an electronic scanning device to convert map lines and points to digital information. Today, many land areas already exist in digital map format and can be freely obtained from the Internet or other means.

Titan GIS is designed to accept and work with data from a variety of input sources. Titan GIS contains map digitising software that is compatible with over 10 different models of digitizers. Titan also provides convenient pre-process functions for scanned images including classification, noise removal and image rectification. Titan GIS supports many GIS data formats including: ArcView Shape, ARC/INFO E00, MapInfo MIF/MID, AutoCAD, DXF/DWG 12~2000, PCI Pix and Arc/Info Grid ASCII Raster file. Titan GIS is also compatible with many image formats such as .BMP, .PNG, .JPG, .PCX, .GIF, .TGA, .TIFF, .WMF, and .PIC.

GRAPHICS AND DATABASE EDITING
Titan GIS provides an array of point, line, and polygon editing tools using the mouse and/or keyboard. Users are able to edit the attributes associated with geographic features while these features are displayed on the screen. Capabilities for editing graphics include add, delete, copy, move, reshape and rotate. In addition, vertices can be added or deleted, lines can be extended, broken or smoothed, and polygons can be added, cut or added to an adjacent polygon. Annotation text can be positioned on a map theme using an interactive approach that allows the annotation to follow the orientation of features. For added flexibility, features can be selected for editing using the cursor or by specifying their attributes.

DATA CONVERSION
Titan GIS has the power to convert any digital map format (vector, raster, TIN) to any other data format (vector, raster or TIN) For example, Titan GIS can convert a vector map layer to a raster format, raster to vector, TIN to raster elevation, etc.

QUERYING MAPS & TABLES
Titan GIS provides users with the ability to inter-query between maps and tables in an efficient and effective manner. Furthermore, Titan GIS supports inter-querying of large-scale exterior databases through its ODBC interface. Inter-querying capabilities include:

· Query an attribute according to its corresponding graphic element
· Query a graphic element according to a specified attribute.

SPATIAL ANALYSIS
Titan ToolBox is a spatial data processing environment in Titan GIS that provides users with tools to perform a variety of spatial operations including theme operation, creating topology, data transformation, projection conversion, buffer analysis, building slope and aspect, etc. Titan ToolBox includes over 50 geographical data processing tools that are displayed alongside the dialogue window in a simply and easy to use format. Some of the tools available to Titan users include theme operation tool, topology tool, vector analysis tool, Raster/TIN analysis tool, data import/export, symbol editor, etc.

Spatial analysis is the combination of analytical techniques associated with the study of locations of geographic phenomena together with their spatial dimensions and associated attributes. Spatial analysis is useful for evaluating suitability, for estimating and predicting, and for interpreting and understanding the location and distribution of geographic features and phenomena. To provide users with a full range of GIS analytical capabilities, Titan not only has the power to perform Vector analysis, but also Raster and TIN analysis. Several techniques for processing and analysing spatial data in Titan GIS are explained below.

• INFORMATION RETRIEVAL
• SPATIAL MEASUREMENTS
• OVERLAYS (DATA INTEGRATION)
• SPATIAL INTERPOLATION
• BUFFERING AND CORRIDORS
• NETWORK ANALYSIS
• DIGITAL TERRAIN ANALYSIS
• MODELS
• MAP PROJECTION
• CO-ORDINATE EXCHANGE
• DATA TRANSFER

TITAN GIS USER INTERFACE
Titan GIS contains a user-friendly interface that is consistent throughout all Titan GIS functions. Programmers and non-programmers can customise the Titan GIS interface to suit their personal preferences by using functions such as show/hide command buttons and menus, edit the keyboard shortcut keys and reorganise or create toolbars.