Dec 11, 2023 · ECI and ECEF are really terms that characterize a coordinate system or a reference frame. I think of them as more like adjectives than nouns. ECI simply means that its origin is at the Earth's center and it's not rotating along with the Earth and ECEF means that its origin is at the Earth's center and it is rotating with the earth.

Nov 7, 2020 · (ECEF could be thought of as a class, just like ECI, except that ECEF is defined with respect to the international reference pole and the international reference meridian -- aka the North pole and the prime meridian. So it truly is a coordinate system)

Sep 14, 2019 · Keep in mind you need some clear definitions of what you mean by ECEF and ECI. Most people utilize WGS84 for ECEF, but that is not a requirement. Similarly ECI could be J2000 or ICRF. In general you will need 4 steps to convert from ECI to ECEF: Calculate earth's precession; Calculate earth's nutation; Account for earth's rotation including UTC ...

Mar 27, 2021 · No problem. I can build the matrix myself so long as I know the X, Y, Z rotations needed to transform J2000 into ECEF. If the z axes of J2000 and ECEF are aligned (e.g., if they both coincide with the earth's polar axis), then all I need is the Z rotation from J2000 to ECEF at one moment in time.

Jun 18, 2022 · Calculate GMST at the TLE epoch time. This will directly yield the transformation matrix between TEME (of epoch) and ECEF. Calculate the time difference in seconds (UT1 or UTC) between the TLE epoch time and observation time. Multiply by $2\pi/86400$. (Alternatively, you may want to use 86400 plus the excess length of day for the epoch time ...

May 31, 2022 · "Real" forces are the same in all Newtonian frames. Gravity is a real force in Newtonian mechanics. The best thing to do is to calculate gravitational acceleration from the perspective of an ECEF frame, and that can include nutation and even polar motion.

I am looking for an Algorithm (the formulas; not the code) to convert from ECEF coordinates to ECI coordinates. I have a MATLAB code for it but am unable to understand certain things. So it'd be helpful if I could get the Algorithm in mathematical form (preferably along with the derivation).

Sep 29, 2022 · Since $\vec{r}_{r}$ can be inter-converted between geodetic and ECEF (geocentric) coordinates, as shown in this Wikipedia post, with minor complication of calculating the latitude, which requires either an approximation or an iterative solution, then given $(\lambda_r, \varphi_r, H_r)$ one can obtain $(x_r, y_r, z_r)$ and vice-versa.

Mar 16, 2022 · I want to compute the distance of a certain satellite, given the TLE, to a ground station in the earth. I have the latitude, longitude and altitude of the ground station. But I don't know if the TLEs are computed using the ECEF or ECI models. Does this question even make sense? Or am I mixing things?

Oct 31, 2016 · I am writing a piece of software which propagates the orbit of a spacecraft from an initial Earth orbit to an interplanetary orbit. My simple two-body propagation works fine in either a geocentric or