ND terrain and weather radar (build 75)

What Zibo does in X-Plane#

• Weather radar: X-Plane's own radar, drawn by X-Plane's EFIS map instrument ("Capt Basemap" in the ND's PANEL_3D, under the compass and the route). zibomod's WXR() sets it from the radar panel:
  • main mode TEST / normal;
  • each side's mode (MAP, WX+M manual, WX+A auto multiscan);
  • gain;
  • the ALT knob (X-Plane's radar altitude);
  • the sector (±60° below 1800 ft with the predictive windshear armed, else ±90°);
  • the radar test (PWS FAIL, WINDSHEAR amber / red on the ND);
  • the ND's mode label.
• Terrain: not Zibo's. The TerrainRadar plugin for X-Plane (by another author) draws it and gives the peak elevations and its look-ahead TERRAIN / PULL UP. zibomod only reads it (TerrainRadar_warning). Without the plugin Zibo shows no terrain (draw_terrain_flag 0, gpws_terr_warn −1: our oracle's state).

Here#

• WXR(), WXR_start_flight() and the knob commands (CMD_wx_*) are translated with the Systems loop. The radar panel's knobs turn (WXR_MAIN_MODE, WXR_CAPTAIN_*, WXR_FIRST_OFFICIER_*). X-Plane's radar settings that WXR() makes are published as L:LU737_WXR_*. The ND's mode label and the radar test flags come from the same code (L:LU737_DU_*).

• In the ND's map slot, MSFS's own map (the SDK's BingComponent; avionics/src/du/NdMap.ts) is placed and turned as zibomod draws the ND:

  • the aircraft at 0.5 / 0.199 (expanded) or 0.48 (centred) of the ND box;
  • a mile 0.136 / 2^range of the box;
  • up is the true heading, or the true track in MAP above 45 m/s.

  It shows with WXR or TERR on, not in PLN.

  • TERR: MSFS's terrain coloured against the aircraft's altitude as the 737's EGPWS display:

    • red above +2000 ft;
    • yellow +1000 … +2000;
    • dim yellow from −500 ft (−250 with the gear down) to +1000;
    • green to −1000;
    • dark green to −2000;
    • black below.

    TERR has the priority over WXR on its side.

  • WXR: MSFS's weather radar (MSFS's own precipitation, what you fly through) in the 737's colours: green, yellow, red. On top of it:

    • gain: the knob scales the colour thresholds (more gain: weaker rain shows);
    • WX+A (auto): the heaviest cores in magenta, as the turbulence a Doppler radar finds in them (an approximation from the rain rate);
    • ALT knob (manual): the returns fade as the scanned altitude leaves the weather. MSFS gives no cloud tops, so this is an approximation (weather taken as 0 – 35000 ft);
    • MAP: the terrain as ground returns;
    • sector: zibomod's ±60° / ±90°.

Not done / limits#

• Terrain peak numbers and the look-ahead TERRAIN / PULL UP: they need terrain elevations, which MSFS does not give a gauge. Planned (owner's choice): from public terrain tiles over the internet.
• The radar's real tilt (beam against the cloud's height): MSFS gives no cloud heights.
• Lightning: MSFS does not expose its own; real-world lightning (Blitzortung) is possible with MSFS's live weather only (owner's choice, off by default).
• Not checked in MSFS yet: the map's placement, colours and the bundle size (MSFS's SDK map adds about 1.3 MB to each ND's script).