A navigation module is normally separate from sensors. For example I worked on the AWADS Adverse Weather Aerial Delivery System, while in the air force. It was a sophisticated system that could theoretically allow a C-130 to take off, fly to a target and deliver by parachute, troops or equipment with zero visibility.
This system consisted on a Navigation unit that did all the calculations, it was paired with a ground mapping radar that the navigator would use to provide the exact position of the craft by making known landmarks.
This is some sort of ground navigation system, how is it going to see ahead to five miles? A high PRF radar can give you some good details, but the limitations you have about moisture don't apply.
Bottom line you need details. How does this system a map, especially since its ground you have to worry about elevation. A large hill or a large rock outcropping in front of you is going to create a blind spot.
You need to figure out how this is going to work. Also unless the vehicle this is in is operated on batteries only, the problem of the drain is a non-issue. The vehicle should have an electrical system that can supply this or have an auxiliary system to provide the necessary power.