Introduction:
Population explosion and resulting demand of appropriate infrastructure facilities are posing serious challenges for the administrators and planners. Trenchless technology has emerged as a major technique for laying utilities without opening trenches. The data on existing utilities however is of utmost importance to avoid damage to existing utilities and safety of personnel. Effective management and planning requires updated maps and information. Recent developments in the area of Science and Technology have provided powerful tools such as Geographical Information System (GIS), Global Positioning System (GPS), Remote Sensing and Geophysics (including Ground Penetrating Radar). These advanced technologies can very effectively be used to handle the present day complex problems related to optimum utilization of available resources and infrastructure. Today it is possible to create on 1:1000 scale Digital Map using high resolution (one meter) satellite imagery and preparation of GIS database in same scale using State Of The Art GIS technology. Further geophysical tools such as Ground Penetration Radar (GPR) can be used for the accurate mapping of the underground infrastructure facilities (Electrical & telecommunication cables, pipelines etc.) to be placed on these maps accurately, rather than relying on historical data, which more often than not is incomplete and inaccurate.
What is GIS?
In the strictest sense a GIS is a computer based program capable of assembling, storing, manipulating and displaying geographically referenced information i.e.; features existing on the ground and their attribute information. Maps and attribute data are stored systematically in this system so that GIS makes it possible to perform following complex analyses:
- Information retrieval: Any required specific information could be retrieved at will from the huge database using simple query operations.
- Overlay: Relationship between various layers (administrative boundaries, buildings, road, rail, and other infra-structural facilities) can be determined.
- Data output: A critical component of a GIS is its ability to produce maps on the screen or paper, which convey the analysis results for the planners and administrators to take decisions. Using GIS planners and decision-makers can map quantities, densities, find what is inside, what is nearby and change detection.
Remote Sensing:
National Remote Sensing Agency (NRSA) is involved in the Aerial surveys using variety of satellites for more than last 25 years. NRSA is continuously receiving satellite data on various resolutions. IRS-1C PAN and LISS-III data has been used extensively by the planners and decision-makers in the past for micro level planning.
Recently NRSA has started selling 1-meter resolution satellite data of Space Imaging (IKONOS). This high-resolution satellite data has added the higher degree of accuracy in the mapping. Small features such as road dividers, buildings, ponds etc. can be identified very easily.
Base Maps Preparation:
Preparation of a reliable basemap is the first step towards data management. Using the tools of GIS and Remote Sensing, base maps can be prepared in a speedy and economical manner:
- Satellite Data of 1-meter resolution (IKONOS) can be purchased from NRSA.
- Satellite images are then registered in the required projection system so that digitized output is achieved in the real ground units.
- Satellite images are digitized in the different layers depending upon the variety of features available on the ground.
- Topology of the various features digitized are created so that actual attribute information of the corresponding feature on the ground can be linked to it.
- Ground surveys are conducted to update the features, which are not visible on the satellite image (Transformers, manholes, electrical poles, telephone poles, etc) and to collect the actual names of the buildings, roads, etc.
- Ground survey data are integrated with the attribute table of the corresponding feature.