I saw Etak back in its early days, and Stan Honey gave me a demo. I still have one of their rate gyro/2D level units, and a compass unit. There's a motor driving a spinning disk, which warps slightly when the unit is turned, and sensors to detect the warp. The level, for sensing which way is down, is a sealed cup of liquid with the liquid height sensed with four capacitor plates outside the cup. The liquid was proprietary, chosen to not slosh under automotive movement. The whole thing is the size of a soda can. The compass is a 2-axis magnetometer, about 2 inches square. It wasn't mounted on a window; it had to be mounted in the horizontal plane, preferably far from metal.
The original Etak units always had the map oriented with north at the top. That was the way sailors used maps. Honey said they'd discovered that about 20% of the population could not cope with a map that wasn't aligned with the direction they were going, which is why they started rotating the map based on vehicle travel. Now everybody does that, and that's why.
The original Etak units always had the map oriented with north at the top. That was the way sailors used maps. Honey said they'd discovered that about 20% of the population could not cope with a map that wasn't aligned with the direction they were going, which is why they started rotating the map based on vehicle travel. Now everybody does that, and that's why.