Hello, Based upon previous experience travelling around high buildings, I anticipate that I'll need to consider an external GPS receiver. Please suggest one--preferably by Apple. Thanks in advance. Leo Bissonnette To change your email settings (unsubscribe, digest only, or vacation mode): http://senderogroup.com/social_media/email.htm Additionally, to unsubscribe send an email to gps-talkusers-request@xxxxxxxxxxxxx with "unsubscribe" in the Subject.