Translation of "featureless" into Japanese

The ground stretches out flat and featureless as far as the eye can see.

地面は,見渡す限り平坦で単調な広がりを見せています。

So how can a navigator find his way across featureless oceans?

では,航海士は何の特徴もない大海原をどうやって進むのでしょうか。