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Radar Scope

The radar scope is a full-screen pure-SVG display of nearby ADS-B traffic. It's modeled after a traditional rotating-antenna radar — concentric range rings, a sweep line, fade-in targets — but driven by GDL90 data from your Stratux or GTX-345.

What you'll see

  • Ownship at the center: yellow dot with a heading triangle
  • Concentric range rings: 1/3, 2/3, full at the configured range
  • Range labels along the right edge (NM)
  • Sweep line: rotating green line that brightens targets as it crosses them
  • Heading label at the top: "↑ N" (north-up) or "↑ HDG 247°" (heading-up)
  • Traffic targets: filled triangles oriented to ground track, color-coded by altitude relative to ownship:
  • Green — more than 500 ft above
  • White — within ±500 ft
  • Amber — more than 500 ft below
  • Trails: dotted line behind each target showing the last 5 NM of track
  • Course-projection lines: dashed line ahead, projecting the next 2 NM
  • Callsign label: tail number / flight ID next to each target
  • Altitude difference: in hundreds of feet (+15 = 1500 ft above you)

Controls

Across the top:

Button Effect
2 / 5 / 10 / 20 / 50 / 100 Range presets in nautical miles
N↑ / HDG↑ Toggle north-up or heading-up display
✦ Sweep / ◯ Sweep Toggle sweep animation on/off
🔔 Alert / 🔕 Alert Toggle haptic alerts on TA/RA
R ≤20 / R ≤50 / R ∞ Cycle the traffic-distance filter
Alt ±2k / ±5k / ∞ Cycle the altitude-difference filter
☂ WX / ◯ WX Toggle the NEXRAD overlay

Range presets vs. auto-zoom

The scope auto-zooms based on traffic and threats:

  • Traffic Advisory (TA) active → range jumps to fit the closest TA target with ~30% margin (typically 5–10 NM)
  • Resolution Advisory (RA) active → range tightens further (typically 2 NM)
  • No alerts, no traffic → 20 NM default
  • No alerts, traffic present → ceil(2nd-furthest target / 5) × 5, clamped to 5–100 NM

When you tap a range button manually, auto-zoom is suspended for 30 seconds. After that it resumes — except a TA or RA always wins regardless of manual override (safety-critical).

Sweep behavior

The sweep is purely cosmetic — it doesn't gate when targets appear. They appear as soon as ADS-B reports them. What the sweep does:

  • Brightens a target when the sweep crosses it (full opacity for ~12 sec fading back to baseline)
  • Adds the visual "feel" of a real radar
  • Can be turned off (especially useful if you find it distracting)

The sweep period is 15 seconds for a full 360° at 10 Hz update rate.

Traffic filtering

Two filter cycles let you hide irrelevant traffic:

  • Range filter (R): drop targets beyond 10 / 20 / 50 / 100 NM (or ∞)
  • Altitude filter (Alt): drop targets beyond ±2k / ±5k / ±10k ft (or ∞)

Filtered-out targets don't render and don't count for threat detection or auto-zoom. Useful when flying near a busy hub — set R≤10, Alt±2k and the scope only shows aircraft you actually need to track.

Threat advisories (TCAS-style)

The scope continuously assesses every visible target for proximity threats. Three tiers:

Tier Range Alt diff What you see Haptic
Approach ≤ 8 NM ≤ 2000 ft Steady amber outline ring None
TA (Traffic Advisory) ≤ 6 NM ≤ 1200 ft Pulsing amber ring Single buzz
RA (Resolution Advisory) ≤ 3 NM ≤ 850 ft Pulsing red ring + halo Triple buzz, repeats every 8 sec

A red banner across the top of the screen names the highest-tier active threat: callsign, range, altitude difference, and (when computable) the predicted closest-point-of-approach time and distance.

Closure-rate promotion

Beyond plain proximity, the scope also computes TCPA (time to closest point of approach) when both ownship and target velocities are reported. If the projected encounter falls inside a higher tier's envelope soon enough, the threat is promoted:

  • Promote to TA if the projected encounter is ≤ 30 seconds out
  • Promote to RA if ≤ 20 seconds out

When this happens, the threat banner shows ⇲ CPA 18s @ 1.2 NM so you can see the encounter geometry, not just current range.

The scope also has a "cleared after passing" rule — once a target has passed CPA (relative motion now diverging) and is ≥ 1 NM away, the alert clears regardless of tier classification. This stops the banner from lingering on a target that's already gone by.

Auto-zoom on alert

When any threat is active and not under manual range override, the scope auto-snaps to a range that contains the threat. This is safety-critical behavior: a TA at 4 NM will force the scope down to 5 NM range (smallest preset that contains the threat with margin) — even if you had it set to 100.

Heading-up vs north-up

Heading-up rotates the entire scope (rings, traffic, sweep) so the aircraft points up the screen and traffic appears in the relative direction it actually is from your nose. Most pilots find this more intuitive in flight.

North-up keeps the screen oriented to true north, which matches charts but requires more mental rotation. Use whichever you prefer.

The button cycles between the two. Your preference is remembered.

Off-range targets

Targets outside the configured range still render at the edge of the scope, marked with a dashed circle around them. That tells you "this target exists but is past your range setting" — useful peripheral awareness.

Doesn't work without traffic

The scope is fed live by the ADS-B receiver. If the receiver is stopped, the scope shows ownship and rings but no targets.