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 areas, 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 areal entity, UFS block is a small area unit. Striking a compromise between the two, the concept of IV Unit was evolved. Traditionally, IV Unit is a well-defined and clearly demarcated geographical area. In terms of number of blocks, an IV Unit consists of about 20 to 40 blocks. UFS block is envisaged to be a compact areal unit with 120-150 households in general and the block is bounded by well-defined clear-cut natural boundaries to the extent possible. The blocks are 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 are so formed that they depict permanent landmarks and corner points, distinguishable from one another and identifiable over time.
3. Till 2017, UFS maps (which are notional in nature and not as per scale), and their boundaries, were prepared and recorded in pen & paper. Notional IV Unit maps were 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.
4. In the latest UFS phase 2017-22, however, large scale changes have been made. This phase is being conducted for the first time in digital mode using the mobile and web applications developed in collaboration with National Remote Sensing Centre (NRSC), Hyderabad. For preparation of UFS maps, boundaries of blocks/wards/IV units/town are being drawn on satellite imagery obtained from Bhuvan portal using QGIS software. Geo-Coordinates (latitudes and longitudes) of a given location are being captured and pushed on satellite imagery through mobile application. Thus, besides QGIS, mobile application is being 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. The boundaries and the attribute data can be accessed through a web portal designed for the purpose. Thus, geo-referenced block/ward/IV unit/town boundaries along with attribute data are being captured in the UFS phase 2017-22. The digital UFS maps will result in easier access and better identification of First Stage Units enhancing the quality of data in the surveys.
