this is the method we record TRPs in India..
Second technique is more reliable and relatively new to India. In picture matching technique people meter continuously records a small portion of the picture that is being watched on that particular television set. Along with this agency also records all the channels' data in the form of small picture portion. Data collected from the sample homes is later on matched with the main data bank to interpret the channel name. And this way national rating is produced.
I got this information from google... i am not the reliable source but yes Google is
related article:
http://articles.timesofindia.indiatimes.com/2010-10-31/open-space/28233595_1_trps-television-rating-points-channel