Where is town map on Pokemon Platinum?

Answer 1

when you get your first Pokemon and the professor tells you to talk to your mother before you leave on your adventure, when you get to the house and talk to your mom, your rivals mother will come in and talk a bit and give you a parcel to deliver to your rival.

Once you deliver that parcel to your rival he/she will point out that there are two town maps in it and give you one

and that's how you get the map