When my students transition from DJI drones that have waypoint missions, GPS modules, and AI tracking, down to a 75mm FPV drone, they’re quick to point out how difficult they are to control: that’s where LiteWing’s Stabilization Module picks up the slack for smaller projects.
Most drones of that size can’t spare a few grams of weight, so a dedicated GPS module is out of the question, and LiteWing has come up with a great Open Source solution.
Most people don’t realize how much “normal” drone flight is propped up by Global Navigation Satellite Systems (GNSS) until they try flying an FPV or DJI drone indoors, or anywhere that a typical DJI drone will enter “Attitude Mode,” which disables the onboard GPS module. The second you lose satellites, the drone stops being “smart” and starts being a nervous little blender that wants to drift into the nearest wall.
What Is This Thing?
This module pairs two sensors that show up repeatedly in unmanned aviation: Optical Flow sensors and Time of Flight (ToF) modules. Hackster recently highlighted the LiteWing Drone Positioning Module, a small add-on board that gives a LiteWing ESP32-based drone the ability to hold altitude and fight drift without access to GNSS (Global Navigation Satellite Systems), such as GPS.
The LiteWing module uses two sensors that make sense together for GPS-denied flight:
- Optical flow sensor (PMW3901)
Optical flow is basically an optical mouse sensor pointed at the ground. It watches the surface texture underneath the drone and measures how that pattern shifts between frames. That shift becomes motion data in X and Y, and it’s combined with other instrument data to navigate.
So if the drone starts “drifting” sideways, optical flow sees it immediately, and the flight controller can push back. That is the core of GPS-denied drift correction.
- Time of flight distance sensor (VL53L1X)
Optical flow alone is not enough because the math changes with altitude. The same “pixel shift” can mean very different real-world movement depending on how high you are above the ground. A time of flight sensor fixes that by measuring actual distance to the surface below, by timing how long it takes a laser beam to return to the sensor.
This is also why GPS-denied position hold tends to feel way better with ToF than without.
The drone itself, separate from the positioning module, is built around an ESP32 flight stack and uses an IMU (MPU6050) for stabilization. That’s your baseline “keep the drone level” sensor package, like the ones you’d find on a 65mm “tiny whoop”. The positioning module is what makes it stop drifting an Olympian on skates.
How Does GPS-Denied Position Hold Work?
This is not a GPS replacement for long-range flights. This is GPS-denied stabilization and position hold, which is a different way to navigate entirely.
The breakdown of how these sensors interact is as follows:
- Optical flow measures horizontal velocity relative to the ground.
- The onboard sensors use that horizontal velocity over time to guess position based on changes from a “starting point”.
- A PID controller applies corrections as it needs.
In my aviation/drone technology classes, we use DJI Tello’s, which are old(er) drones used for educational purposes.
The Tellos also use ToF sensors and Optical Flow sensors to maintain an accurate position hold feature, but they also highlight the downsides, like drifting and sharp drops in altitude.
The Limits of the LiteWing Module’s Hardware
Obviously Optical Flow is not a replacement for a GPS module, and there’s a reason they are used in unison. The texture of a surface, altitude of an aircraft, and dead reckoning drift are all limiting factors when only using these sensors.
By adding an explicit laser range-finder and a GPS module, you’ll be getting the best positioning possible (until you get into RTK).
DroneXL’s Take
This is the kind of GPS-denied tech that actually teaches people something.
A lot of pilots never touch the real problem space. They fly GPS-assisted platforms, hit record, and assume the drone is “smart.” GPS-denied flight removes the training wheels. It forces you to care about sensors, estimation, control loops, and why stability is not free.
LiteWing making this chip modular is a big deal. You can plug it in, test it, tune it in BetaFlight, and learn. You can break it, fix it, and learn more. That is how you build pilots and future engineers that understand autonomy instead of just consuming it.
If you are trying to get into indoor robotics, DIY engineering, or FPV drones, GPS-denied position hold is the lane, and this module is an easy way to get started.
