I recently published a small tutorial on how to create an Enemy Radar screen over here:
In the tutorial you'll learn how to create a radar screen on a UI Canvas that can display the relative positions to the player of different entities or objects with different colors.
You will also learn how to create a small testing environment for the radar, with random walking Enemy and NPC placeholders by using Unity's Navigation system.
Feel free to have a look.
And of course I'd love to know what you think!