With respect to Tamil grammar, what you noticed in dailies is correct, i.e, . The "ra" cannot be a starting alphabet in a noun, always preceded by "e" or "ah" sounding alphabet. It is written as Erameswaram or Ahranganathan against Rameswaram and Ranganathan.
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With respect to standardizing these names, I am not in know if there is any protocol that is followed in writing the name boards. Surely, there has to be some, but again if it so, there cannot be any discrepancies in these. I have also...
more... many times noticed incorrect name boards on trains.