docs: Add docs on launching NaviGator simulation

docs/navigator/index.rst

@@ -25,6 +25,14 @@ Procedures related to operation of the NaviGator AMS.
    Testing Day Checklist <testing_checklist>
    networking
 
+Software
+--------
+
+.. toctree::
+   :maxdepth: 2
+
+   simulating.md
+
 Lessons Learned + Reflections
 -----------------------------
 Lessons we've learned throughout the process that are helpful for future projects.

docs/navigator/simulating.md

@@ -0,0 +1,64 @@
+# Simulating NaviGator
+
+If we had to test all of our new code on the physical build of NaviGator each time
+we made a change, we'd never be able to make changes quickly! Therefore, when
+making changes, it's recommended to simulate them before deploying NaviGator
+in a physical testing environment. Luckily, we have a great simulation environment,
+powered by VRX.
+
+## VRX
+
+[VRX](https://github.com/osrf/vrx) is a simulation environment for aquatic unmanned vehicles, developed by the
+[Open Source Robotics Foundation](https://www.openrobotics.org/). It was originally
+developed for the RobotX competition, and it has continued development in strong
+collaboration with RoboNation, the organization running RobotX. Eventually, the
+VRX competition was launched, which was an exclusively-virtual robotics competition
+that used the VRX platform as a simulator.
+
+VRX is a powerful simulator built on top of [Gazebo](https://gazebosim.org), a standard
+simulator for ROS environments. In VRX, you can customize the vehicle used in the simulator,
+as well as the surrounding environmental conditions (such as the wind, waves, fog,
+and ambient light). Also, the VRX platform typically provides world files and object
+models that are similar to actual task elements used in the biannual international RobotX competition,
+which MIL competes in.
+
+## Launching the NaviGator simulation
+
+To launch the simulation for NaviGator, run the following command in your terminal:
+```bash
+roslaunch navigator_launch simulation.launch --screen
+```
+
+There are some variables you can provide to this launch file to customize the
+simulation environment. These include:
+
+* `use_mil_world`: If `true`, use world files from `navigator_gazebo` (our own
+    ROS package built for NaviGator). Otherwise, use world files from `vrx_gazebo`
+    (aka, world files provided to everyone in VRX). Default: `false`.
+* `world`: Which world file to launch. Typically, there are several world files,
+    each of which will focus on one part of the competition.
+
+## Viewing and inspecting the environment
+
+Now, you've launched the simulation environment, but you're not actually able
+to see NaviGator -- what gives? At this point, you can run one of two commands.
+
+```bash
+gazebogui
+```
+
+`gazebogui` will launch Gazebo, which will provide a beautiful, high-level view
+of the simulation.
+
+```bash
+nviz
+```
+
+`nviz` will launch Rviz, which will give you a much more granular view of NaviGator.
+Here, you can inspect the frames and joints that make up NaviGator, the inputs of
+its sensors, etc.
+
+## Doing things
+
+At this point, it should be just like NaviGator is in the lake -- you can run
+missions, move NaviGator around using `nmove`, or take a peek at the cameras/sensors.