Is RNGFND_LANDING available on Copter?

ArduCopter Copter 4.6
1

I followed the rangeFinder setup documentation, and im a little confused about this part.

" If a rangefinder is oriented facing down, it will be used to for height above ground measurements when within its range for increased landing precision in Copter, and in Plane autolandings if RNGFND_LANDING is enabled. In Copter, when landing and within 10m of the ground according to the range finder, the vehicle will slow its descent to the LAND_SPEED (which defaults to 50cm/s). In Plane, see the “using a rangefinder” section of Automatic Landing"

My rangefinder is setup and working as status shows in missionplannner, but I can’t find the RNGFND_LANDING in the parameter list. Is RNGFND_LANDING only available for planes?

2

Hello,
see those parameters:
EK3_RNG_USE_HGT
EK3_SRC1_POSZ
As far as i know if you defined the range finder well, it will work in auto takeoff and landing automatically until ( rangefinder_limit * EK3_RNG_USE_HGT) other than this baro and gps altitude will be used. You don’t need to change EK3_SRCx_POSZ to have the rangefinder activated in takeoff and landing.

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3

These settings serve completely different purpose and generally shouldn’t be used.

Copter will automatically use rangefinder for correcting altitude targets during landing from what I recall.
See Understanding Altitude in ArduPilot — Copter documentation

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4

What would be the issue if EK3_RNG_USE_HGT is adjusted based on sensor accuracy or to account for an offset? This parameter simply defines the maximum range of the range finder. The system will only rely on the range finder for altitude measurements when the altitude is below a certain percentage of this value.
I also mentioned that there is no need to change the other parameter.

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5

First of all thanks for answering my question. :blush:

So. for my understanding. When the rangefinder is set as downwards position (RNGFND1_ORIENT:25). It will use the rangefinder for ground distance measurement in auto takeoff and landing?
It will bring up my next question: When I use for example AltHold at 5 meter, (my rangefinder is set to 10 meter max) what is keeping my drone at 5 meter? The rangefinder or the gps/baro, or a combination of all 3 (like the masking as for dual GPS option)?

6

This parameter changes how the rangefinder is used by navigation controller and EKF. If you fly over uneven ground, it may seriously upset the EKF position estimate.

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7

If you have the default settings the baro is responsible for maintaining altitude but the rangefinder is used to adjust target altitude as long as there isn’t an excessive change. This way rangefinder upsets are unlikely to negatively affect the EKF state estimate.

If you use EK3_RNG_USE_HGT>0 then EKF state estimate is directly affected and if there are large changes it may be negatively affected as acceleration and altitude won’t agree.

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8

:+1: Thanks for the explanation.

9

Thank you for your response! It really drew my attention to an issue I had but wasn’t aware of until you pointed it out. I went and checked the flight logs and found that the variance in the EKF height increases when I’m within the range of the rangefinder, especially when aggressive attitude angles are applied. While trying to analyze the issue you highlighted, I noticed that this parameter behaves more like a flag rather than applying an offset percentage—contrary to what its description suggests. This makes me feel that it opens the door for user error, just like what happened to me. Lidar in AltHold - #9 by anbello An old issue related to the same parameter were addressed here too.