As Gintas has already found, ...
the numbers refer to longitudes (E or W) and latitudes (N) of the capital cities of:
Rome — ITALY
Tokyo — JAPAN
Port of Spain — TRINIDAD AND TOBAGO
Ottawa — CANADA
The answer can be found in ...
... the names of the corresponding countries:
My 1st is the capital and my 4th is not.
I: I is the first letter of Italy; not sure about the fourth, which I think should also be an I. Is it because a small l, the fourth letter of Italy, looks like a capitalI in a sans-serif font?
My 2nd is falling behind
N: the last letter of Japan.
My 3rd is found thrice, but is not my 5th
D: D and A occur three times in Trinidad and Tobago, and the 5th is A, see below
My 5th is exactly half
A: Half of the letters in Canada are As.
Anyway, I think your friend is in...