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1.3 ArduPilot SITL Installation

What You'll Learn

Install and launch your first virtual drone:

  • What SITL is and why we use it
  • Clone ArduPilot source code
  • Install ArduPilot dependencies
  • Build SITL simulator
  • Launch your first virtual drone
  • Verify SITL works correctly

Time: 45-60 minutes

Prerequisites

Before starting, you must have completed:

What is SITL?

SITL = Software In The Loop

Think of SITL as a virtual drone that runs entirely on your computer: - No physical hardware needed - Same ArduPilot firmware as real drone - Safe to crash and experiment - Perfect for testing code before real flights

Why start with SITL? - Learn without risk of damaging hardware - Test missions before flying - Develop code in safety - Everything you learn transfers to real drones

How SITL Works

SITL and MAVProxy Communication Flow

Clone ArduPilot Repository

cd ~/simtofly_ws/

Clone ArduPilot Source

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

What this does: Downloads ArduPilot source code to your computer.

This takes: 2-5 minutes depending on internet speed.

Expected output: 

Cloning into 'ardupilot'...
remote: Enumerating objects: xxxxx, done.
remote: Counting objects: 100% (xxxxx/xxxxx), done.
...
Resolving deltas: 100% (xxxxx/xxxxx), done.

✅ Success: Clone completes without errors

Verify Clone

cd ~/simtofly_ws/ardupilot/
ls

Expected output: You should see directories like:

Ardupilot Directories

ArduCopter  ArduPlane  ArduSub  libraries  Tools  ...

✅ Success: ArduPilot directories visible

Install ArduPilot Dependencies

Run Installation Script

ArduPilot provides a script that installs everything needed:

cd ~/simtofly_ws/ardupilot/
Tools/environment_install/install-prereqs-ubuntu.sh -y

What this does: Installs compilers, libraries, and tools ArduPilot needs.

This takes: 10-20 minutes (downloads ~2GB of packages).

Expected output:

Install ArduPilot Dependencies

---------- Installing prerequisites for SITL ----------
...
Installing packages...
...
Finished installing prerequisites

✅ Success: Script completes with "Finished installing prerequisites"

Reload Your Profile

The installation script modifies your environment. Reload it: 

. ~/.profile

Alternative (same result): 

source ~/.profile

Initialize Submodules

ArduPilot uses additional code libraries called submodules.

⚠️ Configure Git for Submodules (If Needed)

Most users can skip this step. Only needed if you have git protocol issues or are behind a firewall.

** ⚠️ If submodule update fails in the next step, come back here and run: ⚠️**

git config --global url.https://.insteadOf git://

Then retry the submodule update command.

Checkout Stable Version

We'll use ArduCopter 4.5.7 (current stable as of December 2025): 

cd ~/simtofly_ws/ardupilot/
git checkout Copter-4.5.7

Expected output:

ArduPilot Checkout

Note: switching to 'Copter-4.5.7'.
...
HEAD is now at xxxxxxx ArduCopter: release 4.5.7

✅ Success: Switched to Copter-4.5.7

Update Submodules

git submodule update --init --recursive

What this does: Downloads additional required libraries.

This takes: 5-10 minutes.

Expected output: 

Submodule 'modules/xxx' registered for path 'modules/xxx'
...
Cloning into '/home/.../ardupilot/modules/xxx'...
...
Submodule path 'modules/xxx': checked out 'xxxxxx'

✅ Success: All submodules initialized without errors

First SITL Launch

Initial Parameter Setup

The first time you run SITL, it needs to set default parameters: 

cd ~/simtofly_ws/ardupilot/ArduCopter
sim_vehicle.py -w

Important flags:

  • -w = Wipe parameters and start fresh

What this does:

  • Builds SITL for the first time
  • Sets default ArduCopter parameters
  • Creates configuration files

This takes: 2-5 minutes (first build is slow).

Expected output:

Building ArduCopter...
...
Configuring for SITL...
...
Init ArduCopter V4.5.7
...
Received 500 parameters
...

Wait until you see: Received XXX parameters (where XXX is around 500-600)

Then: Press Ctrl+C to exit

✅ Success: Parameters received, SITL built successfully

Verify sim_vehicle.py is Accessible

The installation should have added sim_vehicle.py to your PATH. Verify: 

which sim_vehicle.py

Expected output: 

/home/your-username/simtofly_ws/ardupilot/Tools/autotest/sim_vehicle.py

If command not found: 

echo 'export PATH=$PATH:$HOME/simtofly_ws/ardupilot/Tools/autotest' >> ~/.bashrc
source ~/.bashrc

✅ Test SITL Launch

Launch SITL Simulator

Now let's launch SITL properly: 

cd ~/simtofly_ws/ardupilot/ArduCopter
sim_vehicle.py -v ArduCopter

What this does: Starts ArduCopter SITL simulator.

Expected output:

Launch SITL Simulator

Starting SITL...
Waiting for heartbeat from 127.0.0.1:5760
...
Init ArduCopter V4.5.7 (xxxxxxx)
...
APM: ArduCopter V4.5.7
...
Received 500 parameters

You should see a prompt: 

STABILIZE>

✅ Success: SITL is running, you're in STABILIZE mode

Test Basic Commands

At the STABILIZE> prompt, try these commands:

Check mode: 

mode GUIDED

Expected response: 

GUIDED>

Arm the motors: 

arm throttle

Expected response: 

ARMED

Disarm: 

disarm

Expected response: 

DISARMED

Test Basic Commands

✅ Success: Commands work, SITL responds

Exit SITL

To stop SITL, press: 

Ctrl+C

Verification Checklist

Before moving to next section, verify:

  • ArduPilot cloned to ~/simtofly_ws/ardupilot/
  • Dependencies installed (install-prereqs script completed)
  • Submodules initialized (no errors)
  • Checked out Copter-4.5.7
  • First launch with -w flag completed
  • sim_vehicle.py accessible from terminal
  • SITL launches and shows STABILIZE> prompt
  • Can change modes (GUIDED works)
  • Can arm/disarm vehicle

All checked? Your SITL is ready!

What You Accomplished

  • ✅ Downloaded ArduPilot source code
  • ✅ Installed all required dependencies
  • ✅ Built SITL from source
  • ✅ Launched your first virtual drone
  • ✅ Tested basic commands (mode, arm, disarm)
  • ✅ Verified SITL installation works

Next Steps

Continue to 1.4 MAVProxy Command Line where we'll:

  • Understand flight modes
  • Control drone via commands
  • Perform takeoff and landing
  • Navigate with basic movements

Common Questions

Q: Why Copter-4.5.7 specifically?

A: This is the latest stable release as of December 2025. It's well-tested and widely used. You can use newer versions when they're released, but this tutorial is verified with 4.5.7.

Q: Can I use a different vehicle type?

A: Yes! ArduPilot supports:

  • ArduCopter — Multirotor drones (what we use)
  • ArduPlane — Fixed-wing aircraft
  • ArduSub — Underwater vehicles
  • Rover — Ground vehicles

Replace ArduCopter with your vehicle type in commands.

Q: What's the difference between -w and normal launch?

A:

  • -w flag: Wipes parameters, sets defaults (use first time only)
  • Normal launch: Uses saved parameters (use after first time)

Q: Do I need to be in ArduCopter directory to launch?

A: No, if sim_vehicle.py is in your PATH. But starting there is good practice.

Q: How much disk space does ArduPilot use?

A:

  • Source code: ~2 GB
  • Built SITL: ~3 GB
  • Total: ~5 GB

Troubleshooting

Error: "command not found: sim_vehicle.py"

Cause: sim_vehicle.py not in PATH

Solution: 

echo 'export PATH=$PATH:$HOME/simtofly_ws/ardupilot/Tools/autotest' >> ~/.bashrc
source ~/.bashrc

Then try launching again.

Error: "Failed to download submodules"

Cause: Network issues or git protocol blocked

Solution: 

git config --global url.https://.insteadOf git://
git submodule update --init --recursive

Error: "Building failed" or compiler errors

Cause: Missing dependencies

Solution: 

cd ~/simtofly_ws/ardupilot/ardupilot
Tools/environment_install/install-prereqs-ubuntu.sh -y
. ~/.profile

Then try building again.

Cause: Python dependencies not installed

Solution: 

pip3 install --user pymavlink MAVProxy

SITL launches but no "Received parameters" message

Cause: First launch without -w flag

Solution: 

cd ~/simtofly_ws/ardupilot/ArduCopter
sim_vehicle.py -w

Wait for parameters, then Ctrl+C and relaunch normally.

"Permission denied" errors during installation

Cause: Trying to install in system directories

Solution: Make sure you're in ~/simtofly_ws/ (your home directory), not /opt/ or /usr/.

Build is very slow

Cause: Limited CPU cores or running in VM

Solution:

  • Be patient (first build takes time)
  • Close other applications
  • Subsequent builds will be faster
  • Consider native Ubuntu instead of VM for better performance

← Back: 1.2 Environment Setup | Next: 1.4 MAVProxy Basics →