I recently funded a project. Several technical details have been hidden due to the technology’s defence applications.

Background

The modern battlefield is a GPS denied environment. Ukraine is a example of this, where Russian’s GPS jamming devices are active. This means that any flying vehicle such as aircraft, missiles, or drones need alternatives for navigation.

I, together with some folks, experimented with such a navigation system.

Note: Several past approaches have been tried to solve this problem, and the following blog by Palantir does a good job of explaining all this → https://blog.palantir.com/the-future-of-drone-navigation-7236075fdedf

Let jump into the method we came up with.

Our idea was as follows →

1. We would have an Camera (onboard the aircraft) that constantly clicks images of the ground, clicking several images per second.
2. An onboard computer analyses the images for pixel transaction i.e. how much the pixels have shifted and in which direction, across two consecutive images.
3. Then, we would translate the pixels movement into actual ground distance. If you do a bit of trigonometry, you will realise that we need the the aircraft altitude to perform this calculation.
4. In order to get altitude, it was suggested that we active systems such as LiDAR or Radar. But then we run into stealth problems for the aircraft.
5. As such we came up with a new method for gauging altitude using purely passive methods.

Fully Passive Altitude Sensing

On the aircraft, we would have two camera’s onboard, that are fixed a set distance apart. Both the camera’s would simultaneously click two images of the ground directly below. Since the camera’s are apart, the two images of the ground below will be slightly different, but will also have overlapping sections as shown below -