Tamil Nadu population through maps

Tamil Nadu population through maps


Christophe Z Guilmoto
IRD, French Institute
PB 33 Pondicherry 605001. India
Email: [email protected]

South Indian Population Information Systems aims at bringing together a large array of social and economic data on CD-ROMs.

In spite of a large and diversified system of data collection, identifying the information available and locating the corresponding publications can prove extremely frustrating in India. Geographic information is even harder to come by since reliable maps are often not available. For lack of proper interface, existing data are often under-utilised as users are unable to track them. It is nowhere more visible than for census data that constitute the richest dataset available on the socio-economic characteristics of Indian villages and towns. Though some census results were made available in a computer format for more than five years, very few people would think of searching over thousands of coded files to retrieve information about a particular village or district. As to the published census volumes that contain local maps and statistics, they are unfortunately printed very late and are once again extremely difficult to locate and use.

In response to this problem, we decided to launch the SIPIS (South Indian Population Information System), a project aimed at bringing together a large array of social and economic data on CD-ROMs. The data were initially assembled in the course of a research programme in demography (the South India Fertility Project), that had been initiated in Pondicherry in 1998 with support from the Wellcome Trust (London), the French Institute (Pondicherry) and the Institut de Recherche pour le Développement (Paris). The original idea was to build a single database of detailed village and town characteristics to study the dynamics of social transformations in South India.

It was decided later to incorporate this information in computerised maps, which meant estimating the geographic locations of all the 70.000 localities in South India. At this point, we soon had to realise that no computerised base maps were available down to the micro-regional level. For our purpose, maps from all possible sources were collected and digitised. We had to patiently patch together village and town maps for each administrative unit and see to it that not too many villages be found in the middle of the sea or on the top of each other! The resulting Geographic Information System (GIS) comprises all census rural and urban localities. These localities were linked to the rich database from the 1991 census that include more than 100 crude attributes and created further indicators on most socio-economic aspects. We gradually added other geographic layers related to aggregate administrative units (taluks, districts, etc.) as well as the most important physical features (elevation, rivers, roads, etc.).

Our team included a demographer cum statistician to check the quality of data, a geographer to tell us what maps are about and two computer experts that had to constantly shuttle between statistical, database and GIS softwares. This project met however with many technical difficulties, often related to the lack of appropriate base maps to positioning of geographic objects. For example, many villages enumerated by the census -especially in tribal or hilly areas- are not shown on any published map. Moreover, South India is changing rapidly, with new roads coming up and a permanent process of administrative redistricting; new districts are created every year while the size of urban limits continues to expand. Therefore, our GIS is far from a final electronic atlas as the pace of change in India is presently more rapid than that of data acquisition. From the original census data, we derived various indicators to be used by all kinds of users, from students and scholars to policy-makers and NGOs. Topics covered were as rich as our database: irrigation, fertility decline, unbalanced sex ratio, urban-rural interaction, population density, social composition of the population, etc. In 1999, we decided to publish our spatialised database in a CD-ROM format in order to share our data and maps to the larger audience. The United Nations Fund for Population (UNFPA, Delhi) agreed to fund this dissemination project in 2000.

As our chart sums up (Fig. 1), the SIPIS was born of the combination of many developments: the interest for local data that are required for decentralised planning, the emergence of powerful GIS solutions that make mapping a child’s play, and theoretical interest for what geographers call spatial analysis. The idea was to allow users to consult the data through maps, with a user-friendly interface. The pilot SIPIS that has been published by the French Institute covers 16,000 villages and 450 towns of Tamil Nadu State, along with contiguous areas of Pondicherry Union Territory. This is a huge database as more than 160 variables are provided for all localities.

Fig. 1: The chart shows that SIPIS is a result of various developments

Data and maps from the CD are now accessible to users through a customised software that include the most common functions of mapping applications: zooming and moving around the map, selection of separate layers of information for display, data retrieval, location of selected localities, classification of localities by specific values, etc. Maps can also be saved as projects or as image files, as well as printed. As a software, SIPIS is very simple to use and requires no specific training. The software developed by our partners in Chennai uses the standard shape format form ESRI. Some trend maps for some important characteristics such as sex ratio or literacy have been prepared separately using powerful geostatistical smoothing techniques such as kriging.

Fig. 2: SIPIS allows the user to retrieve data from maps. The map in the figure shows area around Attur town in Salem district

As said previously, most data have been derived from the last Census of India. Some are absolute figures (e.g., population, area under cultivation, etc.), while others are indicators computed from raw values (e.g. percentages, ratios, etc.). Topics covered include demography (population, households, children, etc.), social and cultural data (Dalits, literacy, etc.), occupational classification (in eleven categories), schooling and health infrastructure, land use and irrigation, communication and transportation facilities. Information on towns and cities is also provided (demography, social and cultural data, occupational classification). This rich information database actually documents the most essential dimensions of social and economic development down to the lowest administrative level. SIPIS allows the user to directly retrieve data from maps (Fig.2). On this map of the area around Attur town in Salem district, Alagapuram village has been selected. A separate window displays the requested data, viz. occupational categories for the village’s working population. The map also shows the other villages (in blue), the drainage system, the roads (in red) and the elevation.

Fig. 3: In this figure, industrialised areas to the North -Chennai, Vellore and the Palar Valley- and to the West -Coimbatore, Tiruppur- are clearly distinguished from the rest of the countrywide where agriculture predominates

A sample of maps is shown (Fig.3). The first is map of taluks in North Tamil Nadu. Taluks are classified by the proportion of the labour working in the agricultural sector (from pink to green). The industrialised areas to the North -Chennai, Vellore and the Palar Valley- and to the West -Coimbatore, Tiruppur- are clearly distinguished from the rest of the countrywide where agriculture predominates. The road network also shown on the road and it tends to become denser in areas with higher urbanisation and industrialisation.

The next map (Fig. 4) shows the valley of the Tambraparani River in the Tirunelveli-Tuticorin area. All individual villages are shown and are classified as per population density. The background map is a trend map of irrigation based on village data and shows that irrigation follows closely the river basins. Towns with their names have been added. On this image, you can also see the SIPIS interface with its menus, buttons and a legend bar on the left.

Fig. 4: The valley of the Tambraparani River in the Tirunelveli-Tuticorin area

It may be of interest to the readers to know that a main source of disappointment was our inability to develop SIPIS in Tamil. We first discovered to our regret that no official listing of village names in Tamil was readily available apart from an old listing dating back to the colonial period. As to our census list of village names in English, the ambiguous transliteration of some Tamil consonants and vowels into English prevented us from doing a systematic “transliteration” into Tamil characters. We also realised that writing a software with menus in Tamil could be a very difficult exercise as computer programs have to be written in Latin script. To close this chapter, should I add that Tamil characters and their corresponding computer codes are not fully yet standardised? As Tamil Nadu is one of the regions most advanced into the information technology revolution, it is to be hoped that these gaps will soon find ingenious solutions and that we can publish the next SIPIS volume with 2001 data in Tamil.

The SIPIS project illustrates how research materials can be fruitfully shared by a large variety of users, especially when it is made available with user-friendly GIS tools. Moreover, our maps points ahead the new census data: from the available maps prepared by the Survey of India, lakhs of localities in India can now be digitised and put on regional maps. As census data will remain the first source of information on India’s social and economic change, mapping them is the next logical step. The Census of India has already started publishing district maps based on its 2001 data, but there remains a need to produce more disaggregated maps to access local data on tehsils, panchayats, urban wards or villages. Combined with other sources on soil, drainage, elevation and communication network, these maps will prove formidable development tools.