backup question

[Ned]

Hi all,

I have a problem decompressing my .gz file from the wanted directory where it is currently into my pwd.
The command I issue is:
tar -xvzf /public_html/ngranic.tar.gz
The public_html directory is a subdirectory in my home user (ngranic) directory, and the one in which I am trying to decompress the compressed .gz file is backup-dir -- also a subdirectory in my user home directory.
The error I get is:
No such file or directory.
I tried with the ~ sign in front of public_html directory name, but it didn't help.
What else I should try?

Many thanks in advance!
Ned