Skip to content

Sensor sanity toolkit

A camera does not measure speed

The single most common error in UAP discussion is reading a velocity off a video. A camera records the projection of a trajectory onto an observation plane, from a moving platform, at an unknown range. Change one assumption about range and the answer changes by an order of magnitude. Here you can do it yourself.

Worked example: GOFAST, January 2015

One of the three US Navy recordings whose authenticity the Pentagon confirmed. It appears to show a small object racing just above the ocean. The values below are taken from the aircraft’s own head-up display, visible on the footage.

This is the one number the video does not give you. Everything else is on the HUD. Drag it.

Sea levelObserverTarget
line of sightthe same line, moments earlier — this rotation is what looks like target motiondepression angle
Range to target
Apparent transverse speed
Own-motion (parallax) component
Implied target speed

What that means

Assumptions of this model — read them
  • The line of sight lies in a vertical plane; the observer’s velocity is treated as perpendicular to it. Real geometry has a crossing angle that reduces the parallax term.
  • A flat Earth over these distances and no atmospheric refraction — both negligible at this scale.
  • The angular rate is the rate of rotation of the line of sight, taken from tracking the object across the frame.
  • The result is the transverse component of the target’s velocity. Motion directly toward or away from the observer is invisible to this method.

02

Aperture shape, not object shape

A defocused point of light takes the shape of the lens aperture. A night-vision device with a triangular aperture turns every distant light into a triangle. This is why the USS Russell “pyramids” are pyramids.

Aperture

03

Angular size proves nothing about size

The same frame is consistent with a small object nearby and a large object far away. Photometry narrows the interval; it never closes it. Drag the distance.

17.5m

Implied object diameter

1.0° × 0.29°

This toolkit is deliberately simple and states its assumptions. It is a teaching model, not a forensic tool — it demonstrates the sensitivity of the result to one unknown, which is the entire point.

Read the GOFAST case file