# ArduPilot SITL Integration

Run the simulation with a realistic ArduPilot flight controller.

## Quick Start (2 Terminals)

**Terminal 1 - Gazebo:**
```bash
gz sim -v4 -r ~/ardupilot_gazebo/worlds/iris_runway.sdf
```

**Terminal 2 - SITL + MAVProxy:**
```bash
sim_vehicle.py -v ArduCopter -f gazebo-iris --model JSON --console
```

## Installation

```bash
./setup/install_ardupilot.sh
source ~/.bashrc
```

This installs:
- ArduPilot SITL
- Gazebo Harmonic
- ardupilot_gazebo plugin
- MAVProxy

## MAVProxy Commands

Once `sim_vehicle.py` is running:

```bash
# Set GUIDED mode
mode guided

# Arm
arm throttle

# Takeoff to 5m
takeoff 5

# Land
mode land

# Disarm
disarm
```

## Available Worlds

```bash
# Iris on runway
gz sim -v4 -r ~/ardupilot_gazebo/worlds/iris_runway.sdf

# Zephyr plane
gz sim -v4 -r ~/ardupilot_gazebo/worlds/zephyr_runway.sdf
```

## Standalone SITL (No Gazebo)

```bash
sim_vehicle.py -v ArduCopter --console --map
```

This opens a 2D map view for testing without Gazebo.

## How It Works

```
Gazebo                    ArduPilot SITL
┌─────────────────┐      ┌─────────────────┐
│ iris_runway.sdf │◄────►│ sim_vehicle.py  │
│ + ArduPilot     │ JSON │ + MAVProxy      │
│   Plugin        │ UDP  │                 │
└─────────────────┘      └─────────────────┘
                              │
                              ▼ MAVLink
                         Your Controller
```

The ArduPilot Gazebo plugin communicates with SITL via JSON over UDP.

## Troubleshooting

**sim_vehicle.py not found:**
```bash
export PATH=$PATH:~/ardupilot/Tools/autotest
```

**Plugin not loading:**
```bash
export GZ_SIM_SYSTEM_PLUGIN_PATH=~/ardupilot_gazebo/build:$GZ_SIM_SYSTEM_PLUGIN_PATH
export GZ_SIM_RESOURCE_PATH=~/ardupilot_gazebo/models:~/ardupilot_gazebo/worlds:$GZ_SIM_RESOURCE_PATH
```

**Can't arm:**
```bash
# In MAVProxy, disable pre-arm checks
param set ARMING_CHECK 0
```