As David notes they would require an external GPS sub-system. There are several ways to do this, frankly I would try stick with the most simple and most reliable. This is not the type of place you want to Rube Goldberg solution. Simplicity rules when it comes to mission critical tasks like navigation.Do all the popular apps require an iPad with 3G/4G ? My iPad is not 3G/4G model. Therefore to use one of these marine nav apps it appears I need a device like GarmiinGLO with Bluetooth to connect directly to GPS satellites to feed my iPad nav app. Is that correct ?
Second question: Can my iPhone Bluetooth with GPS app loaded also feed my iPad nav app?
Right now most of my sailing will be Southwest Florida coast, Charlotte Harbor and possibly Key West. I also have newer Garmin not yet installed from prior owner.