Operation Manual

The Micro VPS is a camera-based system that combines inertial and optical data with satellite imagery to deliver drift-free, high-accuracy positioning.

Failure patterns of the Micro VPS differ from a GPS. For example, while it cannot be jammed, the current version of the system cannot operate in dark environments and will fail if all cameras are obstructed.

We outline below a series of potential pitfalls to avoid when using the Micro VPS for a successful flight.

If you believe we're missing something below, please let us know!

Initialization

It can take a minute for the VPS to initialize. The VPS is waiting for movement to correlate the observed pixel changes from its camera feeds to the measured IMU accelerations and rotations.

During initialization, ensure that Micro VPS is seeing objects or textured elements in its field of view. Gently move the system after powering it on to help with initialization.

Apply some movement to the VPS to help it with initialization.

Pitfalls

VPS relies on 4 cameras and an inertial measurement unit (IMU) to estimate its position. Below are some patterns to avoid when using Micro VPS on your vehicle.

Obstructing all cameras

Much like if you place a GPS inside a building where it cannot receive any signal, obfuscating all cameras will make Micro VPS fail because it is not getting any visual data.

When initializing on the vehicle, make sure Micro VPS is clear off the ground and cameras are not obstructed.

Prolonged vertical movement

The Micro VPS relies on its estimation of the size of the world around it. It correlates inertial measurements with pixel movements to determine how much the vehicle moved during a fixed time interval.

When mission planning, avoid large straight vertical climb (>150m). Such movement can cause correlation issues between the inertial and optical measurements, potentially resulting in failure of the VPS.

Instead, follow a stair stepping pattern which breaks up the vertical climb into multiple progressive stages.

ArduPilot QuadPlane should handle the climb automatically for VTOL aircrafts.

TLDR; don't vertical climb straight for more than 150 m. Break up the climb in several stages.

Prolonged position hold

Theseus is working on a fix to enable longer position holds on quadcopters.

Similar to Prolonged vertical movement, flight modes that hold a position limit the relative movement of pixels. The current version of the firmware supports uninterrupted position holds for up to 60 seconds. Any longer position hold risks causing system failure.

Include movement in your flight plan between periods of position holds or alternatively circle around a small radius to mitigate potential failures.

TLDR; on VPS v1.5.3 avoid position hold for more than 60s. Add some movement between periods.