GIS & RS Based Planning For Power Projects


ANIT GHOSE
Head Technical
GIS & SOFTWARE
Limtex Infotech Limited
anitg@limtexit.com

PROJECT STAGE
After system planning studies and identifying suitable alignment systems from Jamshedpur to Baripada, Reports for the network are to be suggested. At the project stage, detailed elaboration of the project is done for the technical details.

Jamshedpur is situated West Singhbhum district of Jharkhand state at 22.50 N latitude & 86.10 E longitudes. It is surrounded by Chhotonagpur plateau. Baripada is situated Mayurbhanj district of Orrisa at 21.56 N latitude & 86.46 E longitudes. Power grid alignment go through Jamshedpur to Baripada.It should be started at near by Jamshedpur town between river plane of Subarnarekha and NH 33 here it crosses Mohuliya, Ghatshila, Narsingharh these places. At 22.15 N latitude & 86.40 E longitude it cross the Subarnarekha River, now the alignment go through Katra river plane & Burhabalanga river plane between NH 5. In here it cross Kullana and came out side of Baripada town.

Presently, reconnaissance involving the following types of surveys is carried out prior to submission of reports:
  • Map study
  • Walkover survey
Cadastral survey maps with following benefits:
  • Maintenance & additional construction cost can be brought to the minimum.
  • Material Estimation and procurement can be done fairly on realistic basis.
  • Any possible delay/hindrance likely to come during the execution of the work can be avoided after taking due care of various statutory provisions during the course of selecting route alignment.
  • Proper planning can be done for networks keeping provision for future routs etc.
  • Approvals from Railways, Civil Aviation, Forest authorities etc. can be obtained faster.
  • Preparation of Master Network and fixing construction/erection targets can be done on realistic basis, which will help in the judicious planning of materials flow, cash flow and manpower requirements.
  • Appreciable time can be saved during construction & maintenance of roads, if selection of Rivers, route along hill sections and power line etc., are properly made.


MAP STUDY
After drawing various routes of alignment network within the cadastral maps, a comparative study is done on the basis of the following data:
  • Route length.
  • Nos. and type of important road points in each indicating route of each road as measured on the map.
  • Nature and number of major crossings.
  • Mapping the industrial installations, structures, and important places for identification of Roads.
  • Approach to the line in general for construction & maintenance.
  • Reaches through protected or Reserved Forests
  • Continuously long stretches in paddy fields.
  • Close parallelism with Railway lines.
Walkover survey is carried out on these routes. Walk over survey means going over the area associated with the routes and collecting features observed other than those existing on the map. In addition the indications on following features are also checked:
  • Communication lines
  • Power lines (existing)
  • Expanding villages and towns
  • Rich gardens and plantations
  • Reserved forests and high tree areas
  • National Parks & Wild life sanctuaries
  • Archaeological monuments
  • Aerodromes, radar centers etc.
  • Steep sloping terrain, Areas prone to land slides, soil instability etc.
  • Prohibited areas declared under statutory regulations
Preliminary survey: On completion of walkover survey proposal of the most suited route is further studied before taking preliminary survey. The main objective of preliminary survey is to understand the route to the ground with such deviations as may be necessary as per field constraints. It involves generally fixing of important points of the route, identification of major crossings, general classifications of soils, measurement of route length etc. The preliminary survey will include detailed investigations for locations along the route.

EXECUTION STAGE:
On completion of preliminary survey and approval of Feasibility report, the detailed survey of the route is carried out. The detailed survey consists of accurately determining the number and types of roads along with extensions, special road required, number and types of important crossings, special road required etc. It generally involves the following actions:
  • Leveling
  • Plotting and profiling on a scale of 1:25,000
  • Final and pegging of locations
  • Trial pit excavations
  • Detailed soil investigations wherever required
The final output of the detailed survey is in the form of tower schedule showing the type of tower with associated angle of deviation, span length, wind and weight spans, associated foundations along with its classifications, geological and geotechnical, data and any crossing involved in that span.

Limitations of Conventional methods of map study/ surveying Apart from the considerable time involved, the following limitations are generally associated with conventional methods of surveying:
  • The topographical maps used for walkover survey and preliminary survey can be very old and do not contain recent changes in inhabitation pattern, vegetation coverage and water bodies etc.
  • The process of elimination is done at the ground itself, which increases the number of angle towers and length of line.
  • The surveying staffs do not have bird’s eye view of the present ground condition this may particularly result in large inaccuracies in estimation of civil works (benching and revetment) quantities in terrain involving large undulations.
  • There is every possibility of error in recording the ground data and subsequent transfer on the route map
ROUTE PLANNING THROUGH THE FOLLOWING PROCEDURE:
  • Data Input: Survey of India maps, Satellite data, railway maps, land use maps, settlement maps etc are used as input for data base preparation
  • Above inputs through GIS are used to update the maps. Other specific maps may also be created.
  • Using computer run algorithms or linear programming techniques optimal transmission line route may be finalized.
  • On this output from GIS domain post fieldwork is done and location latitude and longitude of the deviation points are identified on ground using existing data.
Further in terrain having large undulations, stereoscopic satellite imageries may be used selectively to interpolate the contours and digital terrain model can be used to select the route in hilly regions.

Detailed Survey Prospect:
Satellite images can be used as a reliable tool to record the precise elevations and plan measurements of the selected route. This may involve taking following actions
  • Transferring of Images to studios for processing and detailed measurements
  • Authentication through ground verification
It is said that camera never speaks lie. That is precisely the greatest advantage of satellite images in detailed survey application w.r.t traditional methods. Further once the ground profile in digital form is obtained the estimation of various types of earthworks involved viz. Benching, revetments etc. can be made using software.

Appropriate techniques for obtaining soil conditions, sub soil conditions, water tables, treacherous terrain conditions etc for accurate estimation of civil works need to be explored.



There may be some error involved in using satellite imagery for preliminary survey due to the “shadow effect”. In the above case it was found sometimes difficult to differentiate between forests and other greenery. Thus exact boundaries of forests could not be demarcated.

  • Resolution plays an important part in interpreting satellite images. Higher resolution may improve the visual content may reveal ground realities more closely.
  • Ground profile and subsoil data cannot be accessed through satellite imageries.
  • Digitization of complete zonal maps rather select features would provide a complete replica in integrated environment.
  • Satellite data of resolution of 1 or 5.8 meter will be preferable. However the overall cost economics shall have to be worked out since this data will be more costly but will completely avoid field works.
  • Symbols of physical features in satellite imageries are not easily recognizable by transmission line engineers.
SPATIAL ANALYSIS :
Maps are a powerful medium for planning, analysis and monitoring for a large number of applications. Satellite images, cadastral maps, political boundaries, contours, networks and locational analysis are handled on a day-to-day basis by decision-makers in numerous organizations. The data of cadastral survey forms the basis for generation of any accurate higher-level map. Spatial analysis applications are of two types:

GIS IN DRAWING CADASTRAL MAPS:
With GIS techniques, maps are produced that are similar in appearance to hand-drawn maps; to the eye, each elevation map may appear to not conflict with the elevation maps of other stratigraphic units. However, to develop a truly internally consistent set of maps, the maps are processed into a vector (grided) format. The survey maps always provide some benchmark and are therefore very useful in contour preparation either manually or electronically. Topographical maps of India made by Survey of India were started more than hundred years ago. Since then the land information is based on the Topo Maps of Survey of India for various purpose. But there is some constraint in Topo maps as information is little bit older. So THESE MAPS could be very helpful to read with the Remote Sensing Images, which is today’s scenario.

Conclusion:
Computer mapping requires two types of databases interacting with each other. One is cartographic database showing, for example, administrative boundaries, roads, rivers, location and shape of houses and buildings. The information sources for acquiring these types of data are satellite and other remote sensing data, existing maps, and land survey data.

The other database is an attribute or thematic database. It may include the names of places and buildings, statistical data such as demographic information, land use classification, and others. These types of data are supplied in various forms such as printed statistical reports, digital tape data, or CD- ROM.

The advantages of computer mapping are the reduced time and costs of data updating and management. Initial data creation and input to develop the geographic database requires long hours of work. We have researched the latest equipment and technology available to produce a workflow system for higher efficiency and improved accuracy.

In order to acquire data directly from satellite, we use a suite of various hardware and software components to operate systems: such as high-resolution Precision photo-scanner and soft-copy ortho-photo mapping system. Other software and hardware components control digitizing tables used to convert existing paper Maps into digital form. Other systems process land survey data from GPS and Total Stations, which collect land, survey data. Original image enhancement and geometric correction of image data are performed with the aid of an image processing system to meet requirements in the latter phase of mapping works.