SITL and MAVProxy

Spring:

git clone https://github.com/ArduPilot/ardupilot

cd ardupilot

chmod u+x Tools/environment_install/install-prereqs-ubuntu.sh

Tools/environment_install/install-prereqs-ubuntu.sh -y

sudo apt-get install gdebi python-matplotlib python-serial python-wxgtk2.8 python-lxml

wget http://firmware.ardupilot.org/Tools/APMPlanner/apm_planner_2.0.26_bionic64.deb

sudo apt install ./apm_planner_2.0.26_bionic64.deb -y

sudo apt upgrade -y

sudo apt check

cd ~/Desktop/

ln -s ~/gps-sdr-sim ./gps-sdr-sim

ln -s ~/ardupilot ardupilot

One way to supply the GPS data is using the MAVLink interface and passing messages to Ardupilot.

I could not get this to work, see update above

https://mavlink.io/en/messages/common.html#GPS_INPUT

https://mavlink.io/en/messages/common.html#HIL_GPS

https://discuss.ardupilot.org/t/fake-gps-via-mavlink-hil-gps-message/26237/3

Fall:

In the HAL of the SITL there is a EPROM parameter we can send. In MAVProxy you can run param get SIM_GPS_GLITCH* to return:

SIM_GPS_GLITCH_X 0.000000 SIM_GPS_GLITCH_Y 0.000000 SIM_GPS_GLITCH_Z 0.000000

The value set here will be passed directly into ardupilot/libraries/AP_HAL_SITL/sitl_gps.cpp (1258):

Vector3f glitch_offsets = _sitl->gps_glitch; d.latitude += glitch_offsets.x; d.longitude += glitch_offsets.y; d.altitude += glitch_offsets.z;

This is a floating point number that will directly be offset to the current simulated position. The resulting position will be sent over the simulated serial pipe.

To help automate test I used two libraries pymavlink and dronekit:

I made a test spoofing script here that has a few helper functions and hardcoded spoofs for X direction:

from pymavlink import mavutil, mavwp

import time

import json

from dronekit import connect, VehicleMode, LocationGlobalRelative

# run sim_vehicle.py -w --console

# pymavlink is used to send raw MAV frames

mavlink = mavutil.mavlink_connection('udpin:0.0.0.0:14551')

# dronekit is used to simiplify to non-raw frames

vehicle = connect('127.0.0.1:14550', wait_ready=True)

time.sleep(2) # Wait for connection

def arm_and_takeoff(aTargetAltitude):

"""

Arms vehicle and fly to aTargetAltitude.

This code is used under Apache 2.0 from Dronekit

https://dronekit-python.readthedocs.io/en/latest/examples/simple_goto.html

Is is unmodified except to provide this copyright notice in accorandance

the FOSS license

"""

print("Basic pre-arm checks")

# Don't try to arm until autopilot is ready

while not vehicle.is_armable:

print(" Waiting for vehicle to initialise...")

time.sleep(1)

print("Arming motors")

# Copter should arm in GUIDED mode

vehicle.mode = VehicleMode("GUIDED")

vehicle.armed = True

# Confirm vehicle armed before attempting to take off

while not vehicle.armed:

print(" Waiting for arming...")

time.sleep(1)

print("Taking off!")

vehicle.simple_takeoff(aTargetAltitude) # Take off to target altitude

# Wait until the vehicle reaches a safe height before processing the goto

# (otherwise the command after Vehicle.simple_takeoff will execute

# immediately).

while True:

print(" Altitude: ", vehicle.location.global_relative_frame.alt)

# Break and return from function just below target altitude.

if vehicle.location.global_relative_frame.alt >= aTargetAltitude * 0.95:

print("Reached target altitude")

break

time.sleep(1)

def setGlitch(axis, size):

#build parameter string

parameter = "SIM_GPS_GLITCH_" + axis.upper()

# Size is a floating point REAL32 to add to axis

mavlink.mav.param_set_send(

mavlink.target_system, mavlink.target_component,

parameter,

size,

mavutil.mavlink.MAV_PARAM_TYPE_REAL32

)

#Adjust airspeed with dronekit

vehicle.airspeed = 40

#takeoff 10 m

arm_and_takeoff(10)

#Print home

print(mavlink.location())

#Hardcoded glitch

setGlitch("x", 0.0002)

time.sleep(4)

setGlitch("x", 0.0004)

time.sleep(4)

setGlitch("x", 0.0006)

time.sleep(4)

setGlitch("x", 0.0008)

time.sleep(4)

setGlitch("x", 0.001)

time.sleep(4)

When we run the SITL simulator with the sim_vehicle.py -w --console, it opens two ports 14550 and 14551. The above python script will connect to the ports once we launch the simulator.

PS: (1) we need to install 'dronekit' Python package. On Ubuntu, 'sudo pip install dronekit'

(2) Assume we already installed MAVLink Python package, which has pymavlink package.

In addition to using this script I add this to a file ~/.mavinit.src:

module load map

map set showsimpos 1

This sets the map up how use it showing the real location.