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Questions tagged [inertial-nav-system]

Questions about inertial navigation systems which sense an aircraft's motion to determine location as it travels.

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Can we use ECI coordinates for an airplane?

It is taught for navigation systems (like an airplane) on Earth we us ECEF (earth-centered, earth-fixed) and for space systems (like a satellite) we use ECI (earth-centered inertial). But why is ECEF ...
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Can you guide me about the purpose of fine alignment in inertial navigation systems?

I am new in inertial navigation field. I have some confusion about fine alignment process of INS. I want to ask that what is purpose of fine alignment? I know by process of alignment we find the ...
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How did KAL 007 get so far off course?

Regarding Flight 007 that got shot down in the Soviet Union, this was reported in the New York Times: Study Says Korean Airliner Was on Its Intended Course When Downed in '83 (nytimes.com) Excerpt: ...
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What does “inertial” refer to in “inertial reference”?

An ADIRU makes use of air data reference and inertial reference. Inertial reference calculates the heading, position, ground speed and attitude. I was wondering why is it called inertial. Is it ...
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How is the drift corrected in INS-driven attitude/heading indicators?

(wikimedia.org) EFIS instruments during a test flight. How is the drift (accumulated error) nullified in INS-driven attitude/heading indicators? The related post 'How are attitude indicators kept ...
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How many Inertial Reference Systems are on a commercial aircraft?

Nowadays all new airplanes have GPS on board so the use of IRS may lose importance, still they must be fitted. How many of them are usually on a commercial aircraft? Does the regulation impose the ...
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What makes inertial guidance unsuitable for auto-land?

Above shows the performance of a Lockheed Martin civilian landing system developed in the mid-90s. It works by using the weather radar in SAR mode to update the INS, and the final 100 ft are flown by ...
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What's the difference between orientation and position?

In INS (Inertial navigation system) sensors, is there a distinction between the following? Orientation (heading, pitch and roll) Position (latitude, longitude and altitude) Is the orientation ...
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How does an ADIRU convert ram air pressure from the Pitot tube into Airspeed?

I know how the analog Airspeed Indicator shows the Airspeed from the ram air pressure from the pitot tube. But I'd like to know how an ADIRU converts the raw pressure data to Airspeed that is ...
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Is it possible to accurately measure airspeed without pitot tube?

This is a follow-up to my previous question: How does this IMU work and how to convert its output into meaningful information? for which many people asserted that I need a pitot tube and a static ...
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468 views

How does this IMU work and how to convert its output into meaningful information?

To understand more about IMUs and IRS, I have chosen the Honeywell 6DF-1N6-C2-HWL Inertial Measurement Unit as an example: I don't see any mention of the output of the IMU in the linked datasheet - ...
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How are IRUs and AHRSs different in terms of their functions? [duplicate]

By my understanding, both systems use gyros and accelerometers to provide aircraft's attitude and heading information. Given that the information they produce are more or less the same, why do the ...
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Do today's aircraft still have INS (inertial navigation system)?

Do today's new aircraft like Boeing 787 still have INS (inertial navigation system)?
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Can cellular towers be used to correct INS drift?

At a high enough altitude a line-of-sight can be established with multiple cellular towers. Can such information be used to accurately correct INS drift (assuming GNSS is not available)?
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How does Kalman filtering work in inertial navigation systems?

As far as I understood it correctly most INS-systems use a Kalman filter to compensate measurement errors. I would like to know: Does the Kalman filter compensate the errors from all the onboard ...
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1answer
601 views

How does the attitude and heading reference (AHRS) work on Boeing 737 aircraft?

I would like to know how the AHRS work on Boeing 737 aircraft. If this aircraft (like every the other ones I guess) has an Inertial Reference System (IRS), composed of 3 accelerometers and 3 ...
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1answer
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Why does Boeing 737 use 2 Inertial Reference Systems (IRS) and GPS?

According to this website the Boeing 737 aircraft use 2 IRS and 2 GPS: IRS L & IRS R. Why? Apparently they are totally independent of each other. Could somebody explain a little bit why they need ...
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What is the difference between IMU (Inertial Measurement Unit) and AHRS (Attitude and Heading Reference System)?

According to online sources like wikipedia the difference belies on the addition of an on-board processing system (I assume it means a microcontroller) which outputs already processed data and not ...
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1answer
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Are the IMU velocities equivalent to the GPS ground velocity, except for the coordinate reference system?

If the velocities measured by the IMU in the body-fixed reference frame are converted into earth fixed frame, are they equivalent to the ground velocity measured using the GPS?
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In an Inertial Measurement Unit, how are the body-axis velocities calculated?

What are body-axis velocity components (u,v,w)? Are they calculated from IMU acceleration components (Ax,Ay,Az)? How can this be related with the airspeed measured from the pitot tube?
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Does the Zenith have anything to do with the read-out of an IRU accelerometer?

Let's say that I have an accelerometer as part of an inertial reference system. Will the position of the Zenith with-respect-to the current position (in terms of rotation) of my accelerometer, have ...
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How does an FMS shift after losing all external navaids?

It's not uncommon for polar flights to lose GPS signal (ionosphere issues due to the high latitudes). But it is not a concern because the typical IRS drift is 650 meters for every hour of flight, and ...
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How to make use of linear acceleration and gyroscope data? [closed]

This is strictly not aviation related so please feel free to move it to the correct section. I have a 9 axis IMU, which gives me yaw, pitch, roll, magnetics, gyros, accels etc. I currently make use ...
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What's the precision of a modern Inertial Measurement Unit, and how is it obtained?

This recent comment reports that: the IMU on new (plane) would localize the aircraft to within 3 feet after a cross-country flight, without any GPS input other than the starting location. I ...
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What is an Inertial Navigation System? How does it work?

In this question, the answer notes that some ADS-B systems are connected to Inertial Navigation Systems (INS), and says they are less accurate than GPS. What exactly is an INS? A couple sub ...