Non-system specific answer
I've always struggled with the rules for knowledge checks. This is mostly because the knowledge categories are ambiguous compared to the definite list of active skills. To compensate for this, I use active skills as a modifier to knowledge rolls. So while the player hasn't specifically stated they have additional knowledge in, say, Medicine, I assume it from the skills they use daily. The character is likely to spend downtime researching his favourite topics.
Using Savage Worlds rules, where every skill is a die type (d6 = average human), I use Smarts plus half the skill die. For example:
Smarts d4, Shooting d10 -> Knowledge (guns) d4+5
Smarts d6, Healing d6 -> Knowledge (medicine) d6+3
Smarts d12, Climbing d4-2 -> Knowledge (mountaineering) d12+0
On top of this, I give each knowledge check an appropriate target. In Savage Worlds:
4: General knowledge: Typical gun capabilities (single-shot, automatic, etc.)
6: Typical subject matter: Make and model of a gun.
8: Specific subject matter: Full capabilities and typical flaws of a gun.
10: Expert subject matter: Identifying a gun and ammunition type from a bullet wound.
In your case, yes I would assume a scholarly character with medical training has more knowledge of medical practices and affairs. Being scholarly, he is likely to have great attention to detail, so I'd give him the full benefits of being scholarly to satellite navigation, but nothing more unless he learns navigation skills.