Hanging participle means that the participle cannot find a logical subject in the sentence, and the absolute construction is the logical subject of the participle. In both cases, the logical subject of the participle is not the sentence subject.

Speaking of Hangzhou, have you ever been there? Speaking of Hangzhou dangling participle,

Spoken English has no logical subject in a sentence.

Weather permitting, we will go for an outing.

Weather permitting is an absolute construction,

The logical theme of permission is the weather.