MAVLINKHUD

Overview

The HOME parameter group (specifically HOME_RESET_ALT) configures how the autopilot handles the reference altitude for the Home Position.

The Home point is the location where the vehicle armed (or where GPS lock was first obtained). It is the target for the Return to Launch (RTL) mode.

Key Concepts

1. Altitude Resets

On startup, the autopilot sets the current altitude to 0. However, if the barometer drifts significantly while waiting for GPS lock, the "Home" altitude might be offset.

  • HOME_RESET_ALT: (ArduPlane) Defines the altitude change (threshold) required to trigger an automatic reset of the 0m reference before takeoff.

Parameter Breakdown

  • HOME_RESET_ALT: Reset threshold in meters.

Developer Notes

  • Library: libraries/AP_AHRS.
  • Safety: Accurate home altitude is critical for ensuring the vehicle clears obstacles during the return flight and lands at the correct height.

HOME_RESET_ALT: Home reset altitude threshold

Description

When the aircraft is within this altitude of the home waypoint while disarmed, it will automatically update the home position. Set to 0 to continuously reset it.

Values

  • Range: -1 to 127
  • Units: m
  • Default: 0

Description

This parameter controls whether and when the autopilot updates its "Home" position while the aircraft is on the ground (disarmed).

  • 0 (Default): Continuously update Home to the current GPS position while disarmed. The altitude is also continuously re-zeroed.
  • -1: Never automatically update Home. Home is set once when GPS lock is first acquired.
  • > 0: Update Home only if the aircraft's altitude is within this many meters of the initial startup altitude. If you move the aircraft significantly up or down (e.g., carrying it up a hill), home updating stops to prevent the barometer from being re-zeroed at the new height.

Source Code

ardupilot/ArduPlane/Parameters.cpp