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Introduction
Human communities cannot exist in isolation, economically, socially or physically. They have to be inter-dependent for the mutual satisfaction of their requirement and also for meeting their basic needs. For meeting their basic needs, they are also dependent on the nature specially the immediate environment. Flux of population in urban territories due to migration from rural areas coupled with rapid growth in population has disturbed the ecological balance. This process hampers the socio economic sustainable development of any region. Expansion of suburban territory with encroachment in prime land is a matter of concern for all and in particular for the authorities associated with the urban planning and development.

Spatial distribution of land use/ land cover information and its changes is desirable for any planning, management and monitoring programmes at local, regional and national levels. This information not only provides a better understanding of land utilization aspects but also play a vital role in the formulation of policies and program required for developmental planning. Planning means the assessment of future and making provisions for it. For ensuring sustainable development, it is necessary to monitor the ongoing changes in land use/ land cover pattern over a period of time.

Urban planning and development is a continuous process and involves planners, administrators, developers, investors and of course, the residents. In order to achieve sustainable urban planning and to check haphazard development, it is necessary that authorities associated with the urban development generate such planning models so that every bit of the available land is used in most rational and optimal way. This requires the present and past land use/ land cover information of the area and pattern of changes with respect to urban settlements and other local resources (Chaurasia, et. al, 1996).

Remote Sensing Based Change Analysis
There are several urban applications where satellite based remotely sensed data are being applied, namely, urban sprawl/ urban growth trends, mapping and monitoring land use/ land cover, urban change detection and updation, urban utility and infrastructure planning, urban land use zoning, urban environment and impact assessment, urban hydrology, urban management and modeling (Raghavswamy, 1994). Remote sensing techniques offer benefits in the field of land use/ land cover mapping and their change analysis. One of the major advantages of remote sensing systems is their capability for repetitive coverage, which is necessary for change detection studies at global and regional scales.

Detection of changes in the land use/ land cover involves use of at least two period data sets (Jenson, 1986). The changes in land use/ land cover due to natural and human activities can be observed using current and archived remotely sensed data (Luong, 1993). Land use/ land cover change is critically linked to natural and human influences on environment. With the availability of multi-sensor satellite data at very high spatial, spectral and temporal resolutions, it is now possible to prepare up-to-date and accurate land use/ land cover map in less time, at lower cost and with better accuracy.

Keeping the above in view, the present work has been undertaken to prepare the multi-date land use/ land cover maps of Allahabad city from multi-sensor satellite data and to monitor the changes in various land use/ land cover classes using digital remote sensing techniques.

Study Area and Data Used
Allahabad district, one of the important parts of Uttar Pradesh State, is situated at the confluence fork of river Ganga, Yamuna and Saraswati, which are held in highest streams by religious minded people in India. For the present work, Allahabad city consisting of urban settlements has been selected. The study area is bounded between the latitudes 25°18'N to 25°35'N and longitudes 81°42'E to 82°00'E.

For monitoring the changes in land use/ land cover, LISS-III digital Data of 2nd December 2000 of IRS -1D satellite along with IRS-1B LISS-II digital data of 20th December 1994 has been used. The path/ row number of IRS-1D imagery is 101/ 54 while the same is 24/50 for IRS-1B. The Survey of India (SOI) topographical map 63-G at the scale 1:250,000 has been used along with other collateral data such as Modified Master Plan 2001 of Allahabad district.

Methodology
The overall methodology adopted for the preparation of land use/ land cover map and change analysis is shown with the help of a flow chart in Figure 1. Digital image processing techniques have been used for preparation of land use/ land cover maps from the multi-date, multi-sensor satellite data. The Anderson's multilevel classification system has been adopted (Anderson, et. al., 1976). ERDAS IMAGINE 8.5 image processing software and its GIS analysis capabilities (VECTOR module) have been used for the preparation of multi-date land use/ land cover maps and to monitor the change pattern.

1 Study Area Image Extraction
The SOI topographical map 63-G was first scanned at 400 dpi resolution and then registered using ERDAS IMAGINE software. For registration, 9 well-distributed Ground Control Points (GCPs) at the intersection of latitude-longitude lines have been selected. The second order polynomial transformation with nearest neighborhood resampling technique has been adopted and a registration error of 0.42 pixels was obtained. Process of image-to-image registration is then adopted for the registration of satellite imagery and modified master plan of Allahabad district on already registered SOI topographical map. The registration error (r.m.s.) obtained was 0.49 pixels for IRS-1D LISS-III data and 0.62 pixel for modified master plan. After this, LISS-II imagery is registered over LISS-III imagery by using 16 GCPs with registration error as 0.38 pixels.

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