heads up display

In Orbiter, the heads-up display is a standard feature of all spacecraft. It has three modes, cycled by pressing the H key; it can also be turned off completely with ctrl-H.

• General information

All HUDs show the current time and camera information in the top right-hand corner. In non-panel modes, they also show engine and RCS status in the top left-hand corner.

• Surface mode

The HUD displays a pitch ladder and a cross-in-circle indicator of the current velocity. (If this overlays the ground, it indicates your projected landing point.) At the top of the HUD is a bearing indicator; this is centred on the vessel's current heading. If a base has been selected in the Map MFD, the direction to that base will be shown as a triangle, either overlaying the bearing strip or pointing off to one side of it. Airspeed and altitude are also shown.

• Docking mode

This mode displays direction and velocity relative to the selected docking target (normally chosen with a nav radio). A box surrounds the target (or a triangular pointer shows the way); a cross shows your velocity vector relative to the target, and a cross-in-circle shows the opposite vector (which could be considered the target's vector relative to you). You can change the reference navigation radio with ctrl-R (which will also cycle through other docking modes; see the manual).

If you want to match velocity with the target, apply thrust towards the circled cross.

If the reference radio is tuned to an IDS transmitter, the HUD will show a series of rectangles aligned with the approach course for the docking port, out to a distance of 500 metres. If the ship is orientated to face inward along the row of rectangles, with the double-line side at the top, it will be in approximately the correct attitude for docking with a front port.

• Orbit mode

This mode displays a pitch ladder relative to the current orbital plane, where the zero line indicates the orbital plane. It also marks the prograde direction with a cross-in-circle and the retrograde direction by with a cross. (If neither of these is on screen, a triangular marker points towards prograde. You can change the reference object with ctrl-R.

A more general discussion of them at Wikipedia: [1]