NavTech servers are used for NAV Coin anonymous transactions. Currently anonymous transaction can only be send from a Full Node wallet or a NAV Coin stakebox (raspberry pi 3).
The NavTech servers are used for processing anonymous transactions. For this a double blockchain setup is used. By default the NAV Coin team NavTech servers are added to the Full Node wallet configuration. You can add other servers by following the tutorial below. The NavTech servers can be found on: https://navtechservers.com/navtech-servers/