National Sample Survey Office (NSSO) has been conducting all India level large scale sample surveys on various socio-economic indicators. Traditionally, a stratified multi-stage sampling design has been followed in the survey conducted by NSSO. A household approach has been adopted for collecting the data in most of the socio-economic surveys. Since the frame for ultimate sampling units i.e. households is neither available nor feasible to be prepared afresh every time on account of time and cost factors, the sampling methods are so designed as to select the households in successive stages. For the rural areas, list of census villages comes in handy as an operationally convenient and readily accessible frame of the first stage units. In the urban area however, the population census does not provide an analogous list of geographical units that could be conveniently adopted as a sampling frame. The Urban Frame Survey (UFS) was conceived and formulated to obviate this particular situation.
2. Under the UFS, each town is divided into certain number of Investigator Units (IV Units) which are further divided into UFS blocks. While town is a big aerial entity, UFS block is a small area unit. Striking a compromise between the two, the concept of IV Unit was evolved. Traditionally, IV Unit was a well-defined and clearly demarcated geographical area. In terms of number of blocks, an IV Unit consisted of about 20 to 50 blocks. Notional IV Unit maps are drawn on A-3 size map sheets. These maps depict lanes, by-lanes, railway lines, canals, etc., which constitutes the boundaries of IV Units/UFS blocks, more or less, in the same manner as they actually occur. They also depict corner points, permanent landmarks and emphasis is to provide as much information as possible in the notional maps leading to identification of the blocks over a period of time. UFS block was envisaged to be a compact area unit with 80-200 households in general and the block was bounded by well-defined clear-cut natural boundaries to the extent possible. The blocks were mutually exclusive and exhaustive so that the blocks carved out in any given town add up to the total area of the town. The blocks were so formed that they depict permanent landmarks and corner points, distinguishable from one another and identifiable over time.
3. However, large scale changes have been made in the latest UFS phase 2017-22. This phase has been planned to be conducted using mobile/ web applications. For preparation of UFS maps, boundaries of blocks/wards/IV units/town will be drawn on satellite imagery obtained from bhuvan portal using QGIS software. Geo-Coordinates (latitudes and longitudes) of a given location will be captured and pushed on satellite imagery through mobile application. Thus, besides QGIS, mobile application will be used as a supplementary tool for drawing UFS boundaries by capturing Geo-Coordinates of the four corner points, in addition to some other points along the boundary, and subsequently joining these points. Mobile application is also equipped to capture the attribute data which was earlier captured through paper schedules. This attribute data consists of landmarks falling in the respective blocks (say, schools, police station, cinema hall etc.), type of area of UFS block (say, bazaar area, slum area, residential area, institutional area etc.) and number of households in each block. Thus geo-referenced block/ward/IV/town boundaries along with attribute data will be captured in the UFS phase 2017-22.