is one piece episode 500 filler?

The episode starts with the base of Ace, Luffy, and Sabo being hit by a windy storm. Luffy had responsibility to look after their pirate flag being "uncool" to lose their flag.

A huge gust of wind comes and blows Luffy off, Ace and Sabo laugh at Luffy. The three brothers go to the Gray Terminal to search for materials to rebuild their hideout being destroyed by the storm.

Luffy wants a telescope, but Ace tells him that they will not find useful things there. On their way to the Gray Terminal, they are being watched by people hidden behind some trees.