Since I cleaned up my data anyway, I thought I might also take a deeper look at an earlier suspicion about Lucknow's urban sprawl. So I mapped the boundaries of the same according to three different datasets - the official ward boundaries notified in the late 1990s (based on census data from 1991), the builtup area as seen from NASA's MODIS satellite in 2002 (which I used in all my maps so far), and now the area in which polling stations had more than one booth in the 2012 assembly elections (which tend to be urban, while rural Lucknow has one booth per station, and one station per village). Here is the outcome (larger version):

The differences between the various datasources can be read in two ways. For one, they use different methodologies to determine the same thing, thus demonstrating how Lucknow looks like when seen as an administrative entity, an area of condensed urban dwelling, and a political unit. But the difference at least in parts also reflects urban growth. In the late 1990s and early 2000s, Lucknow grew mostly towards the North (look at the difference between the green and red boundaries). In the last decade, however, this growth has been redirected towards the South (look at the difference between the red and yellow boundaries). It would be interesting to know how this change came about - especially since extension towards the North (more precisely the North-West, across the river) has been the dominant trend of both planned and unplanned urban growth since independence. Can anybody volunteer a suggestion why Lucknow now changed track and pushed down South?