Radar Tool
PPI display demo
The plan position indicator is the classic radar picture: you're looking straight down on the world with the radar at the centre, north at the top. Click anywhere on the scope to place an aircraft, then watch the sweep find it.
What you're looking at
The rotating line is the sweep — it shows where the antenna is pointing right now. As the beam passes over a target, the echo paints a blip at the matching bearing and range. On the original cathode-ray displays the phosphor kept glowing after the beam moved on, so blips faded slowly until the antenna came round again. That afterglow wasn't a nice-to-have: the fading trail is what let operators see which way a target was moving, one revolution at a time.
Notice the update problem this creates. A rotating radar only looks at each target once per revolution — at 12 RPM, that's one fresh position every five seconds. Fast jets move a long way in five seconds, which is one big reason modern systems use electronically-steered arrays that can revisit a target thousands of times a second without anything physically moving.
Controls
Click (or tap) the scope to place a target where you like. Each aircraft flies a straight track at a realistic speed, so watch its blips step across the screen sweep by sweep.
This demo simplifies reality: every target is always detected, there's no clutter, no noise and no missed scans. It exists to make the geometry and the update rate intuitive — the rest of the radar section covers what makes real detection hard.