AC_Fence: added FENCE_ALT_MIN_TP and FENCE_ALT_MAX_TP #31619

andyp1per · 2025-11-29T17:59:36Z

this allows for fence altitudes to be above ground level, absolute, origin or above home (the default and current behaviour)

This is a rebase of #29761 which I could not push to

this allows for fence altitudes to be above ground level, absolute, origin or above home (the default and current behaviour)

IamPete1 · 2025-11-29T19:16:14Z

Copter avoidance and plane FBWB altitude control will need updating to respect the new frames.

…t fences

andyp1per · 2025-11-29T20:44:34Z

@IamPete1 I have done OA and copter but its not clear to me that there is anything reasonable to do for plane. Plane appears to already be guessing something reasonable. LMK what change in behaviour you would like to see.

ArduCopter/mode_rtl.cpp

IamPete1 · 2025-12-01T22:25:32Z

Plane needs a update here:

ardupilot/ArduPlane/altitude.cpp

Lines 412 to 421 in 2a25847

    
           // taking fence max and min altitude (with margin) 
        
           const uint8_t enabled_fences = plane.fence.get_enabled_fences(); 
        
           if ((enabled_fences & AC_FENCE_TYPE_ALT_MIN) != 0) { 
        
               min_alt_cm = plane.fence.get_safe_alt_min_m()*100.0; 
        
               should_check_min = true; 
        
           } 
        
           if ((enabled_fences & AC_FENCE_TYPE_ALT_MAX) != 0) { 
        
               max_alt_cm = plane.fence.get_safe_alt_max_m()*100.0; 
        
               should_check_max = true; 
        
           }

Probably better to either remove the get_safe_alt_max_m/get_safe_alt_min_m methods or update them to convert to above home alt frame so all the current users are automatically correct.

rmackay9 · 2025-12-03T07:26:46Z

I'd like to give this a test. I just want to be sure that we've tested all the edge cases. Some things to worry about:

RTL alt-frame change when the vehicle is already above or below the fence
When terrain altitude cannot be retrieved
Loiter mode's stopping climbing at the fence. What happens when the vehicle moves forward the terrain falls away below it

peterbarker

Needs autotests.

libraries/AC_Fence/AC_Fence.cpp

andyp1per · 2025-12-03T17:01:59Z

Probably better to either remove the get_safe_alt_max_m/get_safe_alt_min_m methods or update them to convert to above home alt frame so all the current users are automatically correct.

~~Converted to relative frame~~

actually @IamPete1 this turns out to be the wrong change. The maths and checks are much, much simpler if everything is done in the configured frame. The odd one out are these plane methods that require a relative frame, so I have added methods that are specifically relative frame to cope with this particular use case.

pre-arm check for terrain frames update safe alt min appropriately only enable terrain checks if terrain is available introduce get_relative_safe_alt_max_m and get_relative_safe_alt_min_m methods

libraries/AC_Fence/AC_Fence.h

timtuxworth

Some thoughts and suggestions.

libraries/AC_Fence/AC_Fence.cpp

libraries/AC_Fence/AC_Fence.h

timtuxworth · 2025-12-06T20:24:26Z

libraries/AC_Fence/AC_Fence.cpp

+  get our altitude in the FENCE_ALT_TYPE frame
+  return false if not available
+ */
+bool AC_Fence::get_alt_U_in_frame(float &alt, Location::AltFrame alt_frame) const


What is the "U" here? Up? If it's up, altitude is always up isn't it? So not needed?

yeah I could change it, it was just getting very confusing to track the places where things were down instead.

libraries/AC_Fence/AC_Fence.cpp

peterbarker · 2025-12-07T23:36:56Z

libraries/AC_Fence/AC_Fence.cpp

        hal.util->snprintf(failure_msg, failure_msg_len, "Invalid FENCE_ALT_MIN value");
        return false;
    }
+#if AP_TERRAIN_AVAILABLE


This isn't correct; you want this prearm check to fail if your require the terrain database but it isn't available because it is compiled out.

Consider adding it into AP_Arming::terrain_checks instead - it will slot in right next to where we do the same stuff for mission.

peterbarker · 2025-12-07T23:39:02Z

libraries/AC_Fence/AC_Fence.cpp

 }

+/*
+  get our altitude in the FENCE_ALT_TYPE frame


Suggested change

get our altitude in the FENCE_ALT_TYPE frame

get our altitude in the supplied frame

peterbarker · 2025-12-07T23:41:35Z

libraries/AC_Fence/AC_Fence.cpp

+ */
+bool AC_Fence::get_alt_U_in_frame(float &alt, Location::AltFrame alt_frame) const
+{
+    const auto &ahrs = AP::ahrs();


Why aren't you just getting the current location and then asking that for your height in the frame you want?

peterbarker · 2025-12-07T23:44:57Z

libraries/AC_Fence/AC_Fence.cpp

+    return true;
+}
+
+// update safe alt min


Suggested change

// update safe alt min

// update safe alt min - home *must* be set before this function is called

(and in the header file)

... or assert it is set in SITL somehow. Or both.

peterbarker · 2025-12-08T00:24:59Z

libraries/AC_Fence/AC_Fence.cpp

+    if (_alt_min_type == Location::AltFrame::ABSOLUTE) {
+        float home_alt;
+        UNUSED_RESULT(AP::ahrs().get_home().get_alt_m(Location::AltFrame::ABSOLUTE, home_alt));
+        _safe_alt_min_m = _alt_min_m - home_alt - _margin_m;


Suggested change

_safe_alt_min_m = _alt_min_m - home_alt - _margin_m;

_safe_relhome_alt_min_m = _alt_min_m - home_alt - _margin_m;

peterbarker · 2025-12-08T00:30:00Z

libraries/AC_Fence/AC_Fence.h

 #endif

+    // get altitude in alt max frame
+    bool get_alt_U_in_alt_max_frame(float &alt) const { return get_alt_U_in_frame(alt, (Location::AltFrame)_alt_max_type.get()); }


Do we still need the casts here?

peterbarker · 2025-12-08T01:35:51Z

Tools/autotest/arducopter.py

+        home_loc = self.mav.location()
+
+        self.max_alt_fence_frame(0, home_loc.alt + 100)    # absolute
+        self.max_alt_fence_frame(1, 100)    # above home


Can we do a little bit of setup here so home and origin are different altitudes, please?

That really should just be a set_home call.

peterbarker · 2025-12-08T01:37:40Z

Tools/autotest/arducopter.py

-        '''Test Max Alt Fence'''
-        self.takeoff(10, mode="LOITER")
-        """Hold loiter position."""
+    def max_alt_fence_frame(self, frame, alt, terrain=0):


Please pass in an absolute altitude that you expect the vehicle to be close to (+/-5 metres?) when the breach happens and make sure that's about where the vehicle is when it breaches.

AC_Fence: added FENCE_ALT_TYPE

e73a4e6

this allows for fence altitudes to be above ground level, absolute, origin or above home (the default and current behaviour)

andyp1per mentioned this pull request Nov 29, 2025

AC_Fence: added FENCE_ALT_TYPE #29761

Closed

andyp1per requested review from peterbarker and tridge November 29, 2025 18:12

andyp1per changed the title ~~AC_Fence: added FENCE_ALT_TYPE~~ AC_Fence: added FENCE_ALT_MIN_TP and FENCE_ALT_MAX_TP Nov 29, 2025

andyp1per added the WikiNeeded needs wiki update label Nov 29, 2025

andyp1per added 3 commits November 29, 2025 20:43

AC_Fence: specify alt frame for min and max fences separately

65aadca

AC_Fence: add accessors for max alt frame

44f47e1

AC_Avoidance: take alt frame into account when avoiding min or max al…

146de2a

…t fences

andyp1per force-pushed the pr-fence-AGL-update branch from fbbd373 to d5695a5 Compare November 29, 2025 20:43

andyp1per added the DevCallTopic label Dec 1, 2025

tridge reviewed Dec 1, 2025

View reviewed changes

ArduCopter/mode_rtl.cpp Show resolved Hide resolved

IamPete1 mentioned this pull request Dec 1, 2025

AP_Scripting: add access to more fence methods #31603

Merged

CraigElder added DevCallEU and removed DevCallTopic labels Dec 2, 2025

rmackay9 added the NeedsTesting label Dec 3, 2025

peterbarker requested changes Dec 3, 2025

View reviewed changes

libraries/AC_Fence/AC_Fence.cpp Show resolved Hide resolved

libraries/AC_Fence/AC_Fence.cpp Outdated Show resolved Hide resolved

libraries/AC_Fence/AC_Fence.cpp Show resolved Hide resolved

peterbarker removed the DevCallEU label Dec 3, 2025

andyp1per requested a review from peterbarker December 3, 2025 17:02

andyp1per added 4 commits December 6, 2025 19:56

Copter: use fence max alt frame for RTL

0765b61

AC_Fence: record safe alt min/max in relative frame

13f78fa

pre-arm check for terrain frames update safe alt min appropriately only enable terrain checks if terrain is available introduce get_relative_safe_alt_max_m and get_relative_safe_alt_min_m methods

autotest: add alt frame fence tests

f9757e6

Plane: use get_relative_safe_alt_min_m and get_relative_safe_alt_max_m

d8e78e8

andyp1per force-pushed the pr-fence-AGL-update branch from 737bf0c to d8e78e8 Compare December 6, 2025 19:57

timtuxworth reviewed Dec 6, 2025

View reviewed changes

libraries/AC_Fence/AC_Fence.h Show resolved Hide resolved

timtuxworth suggested changes Dec 6, 2025

View reviewed changes

AC_Fence: correct references to frame type

39c31b4

peterbarker requested changes Dec 8, 2025

View reviewed changes

	get our altitude in the FENCE_ALT_TYPE frame
	get our altitude in the supplied frame

	// update safe alt min
	// update safe alt min - home must be set before this function is called

	_safe_alt_min_m = _alt_min_m - home_alt - _margin_m;
	_safe_relhome_alt_min_m = _alt_min_m - home_alt - _margin_m;

AC_Fence: added FENCE_ALT_MIN_TP and FENCE_ALT_MAX_TP #31619

Are you sure you want to change the base?

AC_Fence: added FENCE_ALT_MIN_TP and FENCE_ALT_MAX_TP #31619

Conversation

andyp1per commented Nov 29, 2025

Uh oh!

IamPete1 commented Nov 29, 2025

Uh oh!

andyp1per commented Nov 29, 2025

Uh oh!

Uh oh!

IamPete1 commented Dec 1, 2025

Uh oh!

rmackay9 commented Dec 3, 2025

Uh oh!

peterbarker left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

andyp1per commented Dec 3, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Uh oh!

timtuxworth left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

7 participants

andyp1per commented Dec 3, 2025 •

edited

Loading