Navigation is the art and science of determining the position of a ship, plane or other vehicle, and guiding it to a specific destination. Navigation requires a person to know the vehicle's relative location, or position compared to other known location

Communications on board ship by internal telephone system, voice pipes and portable shipboard transceivers (convey). Engine orders from the bridge by phone or using the ship's telegraph (pass). Communications over short distances can by visual or sound signals (make).
The Commercial Tier is the most commonly used and has been around the longest. Easily the most affordable option, this tier should only be used for smaller yachts and less critical missions. It does not offer the same reliability or advanced features as the two other tier systems.

The Professional Tier System is the middle option, offering better coverage and security than the Commercial Tier. It’s a solid option but it’s not as reliable as the Mission Critical Tier System.

The Mission Critical Tier is the top option offering guaranteed performance. Hence, why it’s used by First Responders like Police Departments and Fire Personnel.