ECEF acceleration in straight and level flight

In summary, ECEF acceleration refers to the acceleration experienced by an aircraft in the Earth-Centered Earth-Fixed (ECEF) coordinate system during straight and level flight. It is calculated by taking into account the aircraft's true airspeed, heading, and altitude, as well as external factors like wind and turbulence. ECEF acceleration is important for accurate navigation and tracking of the aircraft's position and movement, and it differs from other types of acceleration in flight by accounting for the Earth's rotation.
  • #1
Chuck37
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Hopefully this is the right forum. I'm trying to do something I think should be straightforward, which is to describe a straight and level flight over a WGS84 Earth in ECEF coordinates. For example, pick a starting lat,lon,alt,heading and speed and just keep going at that heading and altitude. I'm trying to get evenly spaced time samples with ECEF position, velocity and acceleration.

I can compute ECEF position at the start, then compute a vector that is level to the ellipsoid at that point. If the time sampling is very close I can propagate to the next point and just move along like that and be close to the right answer (I'm slowly climbing because the velocity vectors point up). I'd like to get closer by computing the ECEF acceleration at each point and using that to propagate to the next point too, plus my data will be better if I can provide ECEF acceleration at each point anyway.

Can anyone help? If you know a smarter way to get all the points in one shot, that would be just as good too, I just couldn't figure it out that way.
 
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  • #2

Thank you for reaching out to our forum for assistance with your project. I can understand your frustration with trying to accurately describe a straight and level flight over a WGS84 Earth in ECEF coordinates. This can be a complex task, but I'm here to help guide you in the right direction.

Firstly, it is important to understand that the WGS84 Earth is not a perfect sphere, but rather an ellipsoid with variations in its shape and size. Therefore, your starting position in lat, lon, alt coordinates may not be directly on the ellipsoid's surface, but rather slightly above or below it. This will affect your calculations and could lead to discrepancies in your results.

To accurately describe a straight and level flight over the WGS84 Earth in ECEF coordinates, you will need to take into account the Earth's curvature and rotation. One approach you could take is to use a geodetic coordinate system, such as the WGS84, to define your starting position and heading. Then, you can convert these coordinates to ECEF coordinates using a transformation matrix that takes into account the Earth's shape and rotation. This will give you your initial ECEF position and velocity vectors.

To continue the flight at a constant heading and altitude, you will need to take into account the Earth's rotation and curvature. This can be done by using the Earth's angular velocity to compute an incremental change in the heading and altitude. You can then use this change along with the initial ECEF position and velocity vectors to calculate the next ECEF position and velocity vectors. This process can be repeated for each time sample to get evenly spaced points along the flight path.

To calculate ECEF acceleration, you can use the same approach by taking into account the Earth's curvature and rotation in your calculations. This will give you a more accurate representation of the flight path and can help improve your data.

In summary, accurately describing a straight and level flight over the WGS84 Earth in ECEF coordinates will require taking into account the Earth's shape, rotation, and curvature in your calculations. I hope this information helps guide you in the right direction for your project. If you need further assistance, please don't hesitate to reach out to our forum again.
 

1. What is ECEF acceleration in straight and level flight?

ECEF acceleration refers to the acceleration experienced by an aircraft in the Earth-Centered Earth-Fixed (ECEF) coordinate system during straight and level flight. This coordinate system is fixed to the Earth's surface and takes into account the Earth's rotation, making it useful for navigation and tracking purposes.

2. How is ECEF acceleration calculated in straight and level flight?

The ECEF acceleration is calculated by taking into account the aircraft's true airspeed, heading, and altitude, as well as the Earth's rotation rate and gravitational force. It can be calculated using mathematical equations or through onboard sensors and instruments.

3. What factors can affect ECEF acceleration in straight and level flight?

ECEF acceleration can be affected by external forces such as wind, turbulence, and changes in air density. It can also be influenced by the aircraft's weight, aerodynamics, and engine performance.

4. Why is ECEF acceleration important in straight and level flight?

ECEF acceleration is important in straight and level flight because it allows for accurate navigation and tracking of the aircraft's position and movement. It also helps pilots maintain a stable flight path and avoid deviations from their intended course.

5. How does ECEF acceleration differ from other types of acceleration in flight?

ECEF acceleration differs from other types of acceleration in flight, such as body-fixed or ground-relative acceleration, because it takes into account the Earth's rotation. This makes it a more accurate measure of an aircraft's acceleration in relation to the Earth's surface.

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