Hello,

y> An interesting clue to what is meant by attadiipa is also the words used
y> with it. In this case it is used with sara.na (refuge). Diipa in the sense
y> of island also has a history of meaning of place of refuge, or shelter.

And keeping track of four frames of reference is one's proper range,
ancestral territory, refuge.

See:
http://www.accesstoinsight.org/canon/samyutta/sn47-6.html
http://www.accesstoinsight.org/canon/samyutta/sn47-7.html

Dimitry