Ftp – Resume upload Big files FTP

If security is not concern then prefer ftp over sftp to avoid encryption over head. For files as big as 1 GB I do not think you have worry about people sniffing as users do not usually sniff such big files. So ftp is ok.

You can use WinSCP to perform this kind of automatic upload. It's normally used with SFTP or SCP but it supports plain FTP as well (your server may actually be capable of SFTP or SCP) and this can be automated with their automation scripting:

WinSCP Automation Guide

The specific command you're looking for is keepuptodate:

http://winscp.net/eng/docs/script_commands