Hello DDW,
Thank you for your interest to iSailor app.
if you have some time could you please post the bouy coordinates that are displayed incorrectly - all the charts are prepared based on the latest official information and updated on a regular basis. We will check.
Regarding distance mesurement tool - just tap a pin and hold until the pin is up, both pins are movable. The same approach used for editing waypoints in a route.
If you have any questions please feel free to ask here or via the product web site. We will be happy to help.
Many thanks,
Eugene
Transas Technology Ltd