Most of us inherently trust maps, but maps are actually ‘manipulated reality,’ reality as the map-maker wants us to see it. In India, we go one step further. For a map-maker working with government data, maps are the reality that we can piece together from the clutter of government data sources.

While working with maps for several projects, including with the Transparent Chennai project (www.transparentchennai.com), I too am forced to try and represent reality or come as close to reality as possible. However, when working with Indian data and maps, even without discussing technical issues such as different projection and coordinate systems, more often than not, the simplest task becomes a headache. As a simple example, try ‘googling’ the number of districts in India. From various sources you would come up with 593, 596, 626, 631, 640, 642 etc. While we are familiar with some of the changes our government has made, such as the creation of Uttarakhand (or is it Uttaranchal? more on names later) and Chhattisgarh, most of us would not know of the many changes happening to districts in the country. Taking just the census years from 1961 onwards, the number of districts increased from 339 in ’61 to 359, 414, 472 and finally 594 in 2001. The number today in 2011 could be 600 if you go with the Department of Land Resources, Ministry of Rural Development[1] or maybe 626 or 627 depending on which page of the SAME government owned website[2] you want to believe!

So what does one do when there is data pertaining to a particular year which is to be displayed thematically on a map? Take a dataset of any year and Murphy’s Law will ensure your map is of another year. What do you do with a district such as Ariyalur in Tamil Nadu which features in Census 2001. If you have data pre-2001, you will spend hours figuring out that Ariyalur was part of Tiruchirapalli in 1993 which was then split into 3 districts in 1995 (Karur, Tiruchirapalli and Peramblur). Come 2001 and Peramblur was split into Peramblur and Ariyalur so the once single district in 1993 is now four districts in 2001. But its now 2011 so why look so far back, you say. Fair enough. We have Ariyalur in 2001. Now 2002 comes along and we go back to a combined Peramblur! So Ariyalur disappears! What do you do now with your latest map? You can’t even map the most basic of data sources, the census! But wait, Ariyalur is making a comeback! Forward to 2007 and it reappears! Match your data to your map or your map to your data or just give up?

Let’s take a break from boundary issues for a while and look at names. District names are well… just names right? But if you are trying to automate the matching of data, the name of a district assumes deadly headache-inducing powers. We have already seen how using district codes from Census data is pretty pointless, so we are left with only district names to work with. Anyone who has done a bit of work with maps/ data would have suffered through districts which could be prefaced with West, Paschim, Paschimi; or East, Purbi, Purab, Purba; North, Uttar, Uttara; or South, Dakshina, Dakshin. One could say, no big deal – we know north, south, east, west, just use find-replace operations, problem solved. But what do you do with Alappuzha, Aleppy and Alleppey, or Kannur, Cannanore and Kanoor, or Kollam and Quilon, or Kozhikode and Calicut, or Thiruvananthapuram and Trivandrum, or Thrissur and Trichur? And that’s just from the state of Kerala. In our very own Tamil Nadu, that southernmost place that every 12 year old knows of could be written as Kanyakumari, Kannyakumari, Kanniyakumari if we stick to official names. If the creator of a dataset has split the name into two words or misspelt it, then there are many, many more permutations! But at least they sound similar. What about Sivaganga? It could be Sivagangai or (get this) Pasumpon Thevar Thirumagan or Pasumpon Muthuramalinga Thevar!!

Name-games over, let’s get back to our boundaries, but this time going down to lower levels of administrative boundaries to face some more conundrums. Even if you manage figuring out the difference between blocks, taluks, tehsils and mandals you can rest assured Mr. Murphy and his law will be around to see to it that you have block data and taluk maps. Go down a level or two more to city level and you are guaranteed to have to choose from two or more sources. First, one has to understand the difference between zones, divisions, wards, assembly and parliamentary constituencies and various other terms for varying urban entities and their classifications. For e.g. try to get ward boundaries of Chennai. The Census ward boundaries and the Chennai Metropolitan Development Authority (CMDA) boundaries are so vastly different that there is no reconciling the two. Visit our ‘build a map’ page <http://www.transparentchennai.com/buildamap/> and select ‘Census data by ward boundaries >> Ward boundaries only” and “Ward Boundary (from 2008 CMDA Second Master Plan)” for instant confusion! Obviously, if one is trying to show census data thematically on a map one can’t use the CMDA boundaries even though they seem to correspond better to other sources.

Or try to figure out assembly constituencies. Earlier, the Election Commission helpfully published constituency shapefiles on their site but has now discontinued the practice. So one has to either digitize from other pdfs or jpegs or try to build up shapefiles from published information. One such source is the Chennai corporation website[3] which provides a table listing which wards fall into which assembly constituency. Another source is the website of the Office of the Chief Electoral Office, Tamil Nadu which publishes a pdf giving the same information – which wards fall under which assembly constituencies[4]. So we proceeded to make maps using both sources. The results are below.

Each colour in each of the above maps represents an assembly constituency. So ideally, both maps should look like similar sets of a jigsaw puzzle – even if different colours are used for each piece, their shapes and sizes should be the same. Just one of them – Saidapet towards the lower left corner – looks similar in both maps, but closer inspection reveals a difference of one ward between the two maps. Thus, if one derives maps from the two sources, not a single constituency has a boundary which can be accepted as confirmed from two sources. An attempt to triangulate using a third source may very well throw up a third unique map! Factor in the fact that the city of Chennai is currently in a phase of expanding its city limits to include various village panchayats and all you can do is hope you have enough aspirin to deal with the headache that is sure to follow.

Akshai Abraham with inputs from Prabu R.

[2] http://districts.nic.in/ and http://districts.nic.in/dstats.aspx

[3] http://www.chennaicorporation.gov.in/zone/zoneAddress.htm

[4] http://ceotamilnadu.nic.in/forms/int3.pdf

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