Dear Jonathan,
Thanks for your question and glad you like the concept! The features of AngelNav are in 3 categories:
- Included (free)
- One-off purchase (capabilities)
- Recurrent annual purchase (subscriptions)
The capabilities include items that not everyone wants (eg instruments or race wizard), but once purchased are available for ever.
As you say, charts and tides are annual subscriptions which include access to the charts, the regular updates service and the new notice to mariner service.
It is possible to evaluate almost all the features before purchasing anything. For example, although the included GB Overview chart is small scale, it allows you to play around with waypoints, routes, tracks, and chart work (position lines etc). You can also create satellite charts and see what they look like for any location before buying the satellite capability.
For those with the ability to transmit NMEA data over WiFi, there is an NMEA simulator included free of charge which allows you to test out the AIS and Instrument capability prior to any purchase (full details are in the manual in the app or here).
For subscription charts, you can examine the exact coverage in detail by tapping the (i) button next to the folio in the Store section of the app, or using the tool on the website and zooming in and out (each chart is shown as a blue outline).
I hope that helps.
Bill Aylward