3 ms·

You might be right but I have doubts. Most weapons are INS guided despite the long fly times of cruise missiles etc. ITAR has a massive chilling effect on devel

You might be right but I have doubts. Most weapons are INS guided despite the long fly times of cruise missiles etc. ITAR has a massive chilling effect on development, I wouldn't be surprised if we had error rates of less than a meter a day in mobiles if development wasn't severely curtailed

azernik 8y ago
Cruise missiles combine (using Tomahawk as an example) GPS, visual terrain-matching, radar terrain-matching, and INS. Because they know INS needs those constant corrections.
wahern 8y ago
https://en.wikipedia.org/wiki/TERCOM https://en.wikipedia.org/wiki/TERCOM
ohazi 8y ago
Drift is over a given time, not distance. Missiles generally have an very short fly time, even if they're going really far.
- azernik 8y ago
  Cruise missiles are very different from (quasi-)ballistic or anti-aircraft missiles - they fly at subsonic speeds at low altitudes (usually using a turbojet) to avoid interception. For example, the classic Tomahawk flies at ~900km/h, with the long-range variants having a range of 2500km, giving a maximum flight time on the order of hours, and so a pure INS drift on the order of low hundreds of meters.
dschuler 8y ago
This works the other way - you get to prove your assertion that inertial navigation could work with cheap miniaturized sensors. Anyone can cast a doubt without proof. If your acceleration sensor is off by 1 part per million, 9.8 m/s^2 (i.e. gravity) will turn into a positioning error of ~73km in one day.
rdtsc 8y ago
> Most weapons are INS guided despite the long fly times of cruise missiles etc. And because of a long fly time or imprecise initial reference point (a submarine is floating) some do corrections. One of the coolest one for ICBMs is to use celestial navigation to correct errors. They'd have a window with a camera and would "look" for a few stars.
TickleSteve 8y ago
sensor fusion combines multiple sensors with different characteristics such as: - GPS; widespread, low accuracy - INS; always available, high short-term accuracy, terrible long-term accuracy - terrain-matching: large-scale corrections. The different characteristics allow one sensor to correct another to a degree to produce an overall stable position.

azernik 8y ago

Cruise missiles combine (using Tomahawk as an example) GPS, visual terrain-matching, radar terrain-matching, and INS. Because they know INS needs those constant corrections.

wahern 8y ago

https://en.wikipedia.org/wiki/TERCOM https://en.wikipedia.org/wiki/TERCOM

ohazi 8y ago

Drift is over a given time, not distance. Missiles generally have an very short fly time, even if they're going really far.

azernik 8y ago
Cruise missiles are very different from (quasi-)ballistic or anti-aircraft missiles - they fly at subsonic speeds at low altitudes (usually using a turbojet) to avoid interception. For example, the classic Tomahawk flies at ~900km/h, with the long-range variants having a range of 2500km, giving a maximum flight time on the order of hours, and so a pure INS drift on the order of low hundreds of meters.

dschuler 8y ago

This works the other way - you get to prove your assertion that inertial navigation could work with cheap miniaturized sensors. Anyone can cast a doubt without proof. If your acceleration sensor is off by 1 part per million, 9.8 m/s^2 (i.e. gravity) will turn into a positioning error of ~73km in one day.

rdtsc 8y ago

> Most weapons are INS guided despite the long fly times of cruise missiles etc. And because of a long fly time or imprecise initial reference point (a submarine is floating) some do corrections. One of the coolest one for ICBMs is to use celestial navigation to correct errors. They'd have a window with a camera and would "look" for a few stars.

TickleSteve 8y ago

sensor fusion combines multiple sensors with different characteristics such as: - GPS; widespread, low accuracy - INS; always available, high short-term accuracy, terrible long-term accuracy - terrain-matching: large-scale corrections. The different characteristics allow one sensor to correct another to a degree to produce an overall stable position.