There are three gadgets that, when used wisely, make up for the lack of a central radar:
1) A motion sensor, which shows everything that is currently moving around you in a radar-like display. This only shows moving objects, so both an animal and a person show up as a dot. And only if they're moving.
2) A sonar that emits a pulse that shows you everything that is in an area, so it will detect still objects as well. It also does not differentiate between human and animal, and additionally, a person or animal can possibly hear the pulse.
3) An anti-personnel sensor that has no visual component. But it both beeps and makes your controller vibrate when it detects a person nearby; the beeping is heard only by you, and increases in frequency the closer you get to someone.
So, no, there's no central radar, but between these three items, you basically have a radar of sorts. You just can't tell where people are looking, but that's what peeking around corners and stuff is for.