Geofence

Description

A geofence check is done:

  • whenever a new mission is sent to the autopilot
  • the current position of the system is updated

On a violation of the geofence a warning is printed in qGroundControl.

Setup

Geofencing is enabled if the file fs/microsd/etc/geofence.txt exists and the parameter GF_ACTION is set to 0 = none, 1 = warning (default), 2 = loiter, 3 = return to launch, 4 = fight termination.

GF_COUNT sets the number of subsequent 'outside of geofence' detections (= positions measurements) which are needed before the geofence violation is triggered. This parameter can be used to make the fence more robust against gps/estimator glitches.

Source and altitude mode

  • The param GF_SOURCE defines which position source is used: 0 for global position (position estimator), 1 for raw gps
  • The param GF_ALTMODE defines which altitude reference is used for the vertical geofence limit. O: wgs84 (AMSL from GPS), 1: QNH (altitude calcualted from barometer + local ground offset (QNH))

File format

fs/microsd/etc/geofence.txt holds the points for the geofence polygon. There are two options for the coordinate format: Decimal degrees and the Degree-Minute-Second Format. The first line always holds the vertical limits in meters AMSL (altitude_min altitude_max). For a minimal altitude which corresponds to the ground set the lower vertical limit to a value « 0.

Example: Decimal Degrees

0 900
47.475273548913222 8.52672100067138672
47.4608261578541359 8.53414535522460938
47.4613484218861217 8.56444358825683594
47.4830758091035534 8.53470325469970703

Example: Degree-Minute-Second

0 900
DMS -26 -34 -10.4304 151 50 14.5428
DMS -26 -34 -11.8416 151 50 21.8580
DMS -26 -34 -36.5628 151 50 28.1112
DMS -26 -34 -37.1640 151 50 24.1620

Geofence files for OBC

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