A drone that stays overhead: building autonomous dispatch for campus safety

A student leaves the library at midnight. She presses one button, and a drone flies out to meet her.

Most safety apps are alarms: you press them once something has already happened. This one was built for the twenty minutes before that, when someone knowing where you are is what changes the outcome.

The pilot approves; the aircraft flies itself

The request goes to a pilot covering that part of campus, who sees the route, the wind and the visibility, and taps dispatch. From there the aircraft runs a six-step sequence: it takes off, holds a five-second hover so it settles before a mission is sent, builds a waypoint route from the student's live location and flies it.

While it flies, the system re-checks the student's GPS every two seconds until the drone is overhead.

Hover, not return home

Most drone missions end by flying back. This one ends in a hover, because the whole point is that it stays with the student for the rest of the walk. It is a one-line decision that defines the product.

Four codebases for three kinds of people

A student, a pilot and a campus operator need completely different tools, so the system is two mobile apps, a native pilot app and a 31,000-line operations console. The student app ships in four languages with the same 327 strings in each, because campus safety apps are used disproportionately by international students.

The lesson we took from it: the impressive feature is rarely the hard part. The edge cases are.