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The objective of this study is to develop an application of Decision support System for the selection of optimized power transmission line route using computerized user interactive conceptual model with an integrated GIS environment. The various physical features of study area have to be considered to ensure adequacy of planning to meet multitude of objectivities.
This requires an understanding of the complete ground situation of various physical spatial features, facilities and the socio-economic parameters of the study area by conducting a comprehensive field survey.
The scope of the work covered route alignment using satellite imageries of NRSC and survey of India (SOI) Toposheet maps. Three alternative route alignments were identified and the optimized route alignment was selected. The output is to be in the form of digitized route alignment drawings with latest topographical and other details / features up to 8 Kms on both sides of the selected route alignment.
3.3.3 DATA INPUT FOR BASE MAP
SOI toposheets based on the index map and buffer area, the active project study area will be fixed and the respective toposheets of scale 1:250000 (1° X 1°) will be procured from the maps division of SOI.
Satellite Imageries from NRSC (IRS-PAN/LISS III / Merged data) for the proposed project area.
Geo-referencing of the toposheets and satellite imageries will be carried out using image processing software such as ERDAS imagine.
Toposheets would be scanned to create raster files pertaining to the project area. These raster files would be geo-referenced based on the latitude & longitude information derived from the toposheets. After geo-referencing, the maps (1:250000 scale) shall be edge matched and a digital mosaic prepared which depicts the continuity of the project area.
For geo-referencing satellite imageries, sufficient number of well distributed ground control; points would be selected in correspondence with the relevant toposheets. Care is to be taken to satisfy the condition on density of GCPs for image registration.
Digitize the land base data using Geo-referenced SOI maps as backdrop in AUTOCAD and digitize all the required features at 1:1scale. Based on grid reference, the corresponding image will be called for data capture. All features in the image will be put on appropriate layers. The cartographic contents in terms of color schema, lettering standards, symbology, layer naming convention etc, as agreed with POWRGRID CORPORATION will be captured.
The following are the layer wise information that will be digitized from SOI toposheets.
All major & minor roads.
Water bodies like rivers, canals and first order streams.
Elevation contours and spot heights.
Power and communication line crossings.
Boundaries of following
Reserved forest and vegetation
Play grounds, wild life sanctuaries, parks, stadiums and airports
3.3.6 UPDATION OF BASE MAP
The SOI toposheets which is of 30-35 years old shall experience so many changes either in form of change in rivers, drainage course or settlements etc, but local authorities are still dependant on existing topographic maps which are absolutely out dated. If these maps are updated, several aspects of management by the concerned departments can be streamlined. Through experience IRS-IC/ID high-resolution images are best suited in context with mapping and monitoring of changes referencing will be carried out in ERDAS imagine software. The Geo-referenced image would be further mosaic and will subsequently used for data updation.
3.3.7 GENERATION OF THEMATIC LAYAERS
The following spatial themes are generated for the present work.
Transportation Network Map
Major Roads ( NH and SH ) and other roads
Existing Power Lines Map
Alternative Routes Map ( Three different routes on same corridor )
Wind Zone Map
River and Canal Network Map
3.7 DATABASE DESIGN
The Geographical Information System (GIS) has two distinct utilization capabilities -the first pertaining to querying and obtaining information and the second pertaining to integrated analytical modeling. However, both these capabilities depend upon the core of the GIS - the database that gas been organized. Many a GIS utilization has been limited because of improper database organization. The importance of the GIS database stems from the fact that the data elements of the database are closely interrelated and thus need to be structured for easy integration and retrieval. The GIS database as also to cater to the different needs of applications. In general, a proper database organization needs to ensure the following
Flexibility in the design to adapt to the needs of different users.
A controlled and standardized approach to data input and updating.
c) A system of validation checks to maintain the integrity and consistency of the data elements.
A level of security for minimizing damage to the data.
Minimizing redundancy in data storage.
While the above is a general consideration for database organization, in a GIS domain the considerations are pertinent with the different types and nature of data that need to be organized and stored.
The data in GIS broadly categorized, the basic data for the GIS database has two components:
a) Spatial data - consisting of maps and which have been prepared either by field surveys or by the interpretation of Remotely Sensed (RS) data. Some examples of the base maps are the existing power lines map, transportation map etc.
b) Non-spatial data - attributes as complementary to the spatial data and describe what is at a point, along a line or in polygon and as socio-economic characteristics from census and other sources. The attributes of a power line could be the name, voltage level category, material-type, length etc.
The non-spatial data is mainly available in tabular records in analog form and need to be converted into digital format the non-spatial data is mainly in tabular records, which are stored to layers at the time of digitization using ArcMap.
GIS database design:
Just as in any normal database activity, the GIS database also needs to be designed so as to cater to the needs of the application that proposes to utilize it. Apart from this the design would also: -
Provide a comprehensive framework of the database.
Allow the database to be viewed in its entirely so that interaction and linkages between elements can be defined and evaluated.
Permit identification of potential problematic areas so that design alternatives can be considered.
Identify the essential and correct data and filter out irrelevant data.
Define updating procedures so that newer data can be incorporated in future.
The design of the GIS database will include three major elements.
Conceptual design, basically laying down the application requirements and specifying the end-utilization of the database. The conceptual design is independent of hardware and software and could be a wish list of utilization goals.
Logical design, which is specification of the database to a particular GIS package.
This design sets out the logical structure of the database elements determined by the GIS package.
Physical design, which pertains to the hardware and software characteristics and requires consideration of file structure, memory and disk space, access and speed etc.
Each stage is interrelated to the next stage of the design and impacts the organization in a major way.
GIS-Core of the Database:
The Geographical Information System (GIS) package is the core of the GIS database, as both spatial and non-spatial databases have to be handled. The GIS package offers efficient utilities for handling both these datasets and also allows for the spatial database organization; non-spatial datasets organization - mainly as attributes of the spatial elements; analysis and transformation for obtaining the required information; obtaining information in specific format (cartographic quality outputs and reports); organization of a user-friendly Query-system.
5.5 Components of GIS:
GIS constitutes of five key components:
It consists of the computer system on which the GIS software will run. The choice of hardware system range from 300MHz Personal Computers to Super Computers having capability in Tera FLOPS. The computer forms the backbone of the GIS hardware, which gets it's input through the Scanner or a digitizer board. Scanner converts a picture into a digital image for further processing. The output of scanner can be stored in many formats e.g. TIFF, BMP, JPG etc. A digitizer board is flat board used for vectorisation of a given map objects. Printers and plotters are the most common output devices for a GIS hardware setup.
GIS software provides the functions and tools needed to store, analyze, and display geographic information. GIS softwares in use are MapInfo, ARC/Info, AutoCAD Map, etc. The software available can be said to be application specific. When the low cost GIS work is to be carried out desktop MapInfo is the suitable option. It is easy to use and supports many GIS feature. If the user intends to carry out extensive analysis on GIS, ARC/Info is the preferred option. For the people using AutoCAD and willing to step into GIS, AutoCAD map is a good option.
Geographic data and related tabular data can be collected in-house or purchased from a commercial data provider. The digital map forms the basic data input for GIS. Tabular data related to the map objects can also be attached to the digital data. A GIS will integrate spatial data with other data resources and can even use a DBMS, used by most organization to maintain their data, to manage spatial data.
GIS users range from technical specialists who design and maintain the system to those who use it to help them perform their everyday work. The people who use GIS can be broadly classified into two classes. The CAD/GIS operator, whose work is to vectorise the map objects? The use of this vectorized data to perform query, analysis or any other work is the responsibility of a GIS engineer/user.
And above all a successful GIS operates according to a well-designed plan and business rules, which are the models and operating practices unique to each organization. There are various techniques used for map creation and further usage for any project. The map creation can either be automated raster to vector creator or it can be manually vectorized using the scanned images. The source of these digital maps can be either map prepared by any survey agency or satellite imagery.