Through a scope.

If i choose to snipe it's either un my commando Cko (so Iit take you more than 1 strike to kill me ) or in my scout Cko with 3 complex precision mods and 2 range amps you'd be surprised how many knifers iv turn round and blapped with my bolt pistol.

I played sniper main for the first year playing dust.
With ewar skills maxed and maxed proto profile modules.
I never ever saw someone killing me in my radar.
Gallente lv 5 logistics sniper too

I think when you are looking through scope,
no enemies appear in your radar.
I do detect scouts passively when not zoomed in to scope.

This coupled with the concentration during scoping,
trying to get headshots, is a 100% chance to kill a sniper if you go behind them.

There was this hilarious one time, I was using kaalakiota.
I got up to go higher up a hill, 3 scouts were up there.
They had spotted me and were coming down to kill me.
I had 1 second to react, i started shooting as fast as i could, not aiming.
I headshotted the first 2 front scouts, and the third took a step back.
Not so confident 1 on 1 now. He was standing there thinking what to do.
I crouched down, took aim with scope, and last 3 shots got him.
My amazing dust514 moment. The chance of headshots on the first 2 scouts
was like winning the lottery.