A dangling modifier is an error caused by not placing the noun being modified next to its modifier (or failing to use the noun being modified in the sentence).
Having seen Blackpool Tower, the Eiffel Tower is more impressive.
modifier the noun being modified
The example above intimates that the Eiffel Tower has seen the Blackpool Tower. A correct version would be:
Having seen Blackpool Tower, I am more impressed with the Eiffel Tower.
This version is correct, because "I" is logically attached to "Having seen Blackpool Tower". (Note: "I" is a pronoun: a type of noun.)
Being born in Dawlish, it is understandable that I miss the sea so much.
modifier pronoun being modified
In this example, "it" was not born in Dawlish. Better versions would be:
Being born in Dawlish, I understand why I miss the sea so much.
As I was born in Dawlish, it is understandable why I miss the sea so much.
("As I was born in Dawlish" is not a modifier.)
Glossary of grammatical terms
Click on the one which is NOT a dangling modifier: