fix(navigator): honor NAV_LAND mission item abort altitude (param1)

[anoshyn]

A MAV_CMD_NAV_LAND mission item carries a param1 "minimum abort altitude" (the height above the landing point to climb to if the landing is aborted; 0 = use the system default). PX4 parsed and dropped it — there was a long-standing // TODO: abort alt param1 — so an aborted landing always climbed to the global MIS_LND_ABRT_ALT, ignoring the per-item value.

This carries param1 in the otherwise-unused time_inside field on upload (nothing reads time_inside for a LAND item), and in MissionBase::do_abort_landing() uses it as the climb-above-landing-point height when set (> 0), falling back to MIS_LND_ABRT_ALT otherwise. The value also round-trips on mission download (the reverse format_mavlink_mission_item() TODO is resolved too).

• Items with param1 = 0, including missions stored by older firmware (parsed into a zero-initialized item), keep using the MIS_LND_ABRT_ALT default — no behavior change for existing missions.
• Normal (non-aborted) landings are unaffected; time_inside is not consumed for LAND items elsewhere.
• Scope is fixed-wing NAV_CMD_LAND aborts, matching the existing abort behavior; VTOL_LAND is unchanged.
• MIS_LND_ABRT_ALT parameter docs now note it is the default when the item doesn't specify its own abort altitude.

Fixes #27290

[github-actions]

🔎 FLASH Analysis

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Updated: 2026-05-30T12:45:40

[Copilot]

Pull request overview

Fixes a long-standing TODO so that MAV_CMD_NAV_LAND's param1 (per-item minimum abort altitude above the landing point) is no longer silently dropped. The value is stashed in the unused mission_item_s::time_inside slot on upload, read back in MissionBase::do_abort_landing() (falling back to MIS_LND_ABRT_ALT when zero/unset), and round-tripped on mission download.

Changes:

• Parse param1 from MAV_CMD_NAV_LAND into mission_item->time_inside and emit it back from format_mavlink_mission_item().
• Use _mission_item.time_inside (when > FLT_EPSILON) as the abort climb-above-landing-point height in MissionBase::do_abort_landing().
• Clarify the MIS_LND_ABRT_ALT parameter description as the default when LAND param1 is unspecified.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/modules/mavlink/mavlink_mission.cpp	Stores/restores MAV_CMD_NAV_LAND param1 via mission_item.time_inside; removes both abort-alt TODOs.
src/modules/navigator/mission_base.cpp	Uses the per-item abort altitude (from time_inside) when computing the abort loiter altitude, falling back to MIS_LND_ABRT_ALT.
src/modules/navigator/mission_params.yaml	Documents MIS_LND_ABRT_ALT as the default when the LAND mission item doesn't specify its own abort altitude.

[hamishwillee]

@julianoes FWIW the problem here isn't that this doesn't implement this param, it's that we don't support it and we don't fail the upload with MAV_MISSION_INVALID_PARAM1.

But anyhow, would appeciate your thoughts on #27483

EDIT - because it would be nice to also reject a non-NAN param3, or any values of PRECISION_LAND_MODE that we don't support.

[julianoes]

Yes, we should fail the upload, I agree there.

[anoshyn]

I’ll keep unsupported-param rejection as a follow-up. This PR now only preserves and uses NAV_LAND param1 for the abort altitude, with a named land_abort_min_alt alias and a finite-value guard before consuming it.

Rejecting unsupported NAV_LAND params like non-NaN param3 or unsupported precision-land modes is the right direction, but it is broader mission-upload validation work and fits better under #27483

[julianoes]

Looks good. Any objections before I merge?

[hamishwillee]

Looks great to me (assuming latest version tested). We should update #27541 to note the change so that it doesn't get rejected.