Convert Earth-centered inertial (ECI) coordinates to azimuth coordinates
Utilities/Axes Transformations
The ECI Position to AER block converts Earth-centered inertial (ECI) position coordinates to azimuth, elevation, and slant-range coordinates (AER), based on the geodetic position (latitude, longitude, and altitude).
Azimuth (A) — Angle measured clockwise from true north. It ranges from 0 to 360 degrees.
Elevation (E) — Angle between a plane perpendicular to the ellipsoid and the line that goes from the local reference to the object position. It ranges from –90 to 90 degrees.
Slant range (R) — Straight line distance between the local reference and the object.
Reduction method to convert the coordinates. Select either:
IAU-76/FK5
Reduce the calculation using the International Astronomical Union 76/Fifth Fundamental Catalogue (IAU-76/FK5) reference system. Choose this reduction method if the reference coordinate system for the conversion is FK5.
This method uses the IAU 1976 precession model and the IAU 1980 theory of nutation to reduce the calculation. This model and theory are no longer current, but the software provides this reduction method for existing implementations. Because of the polar motion approximation that this reduction method uses, the block calculates the transformation matrix rather than the direction cosine matrix.
IAU-2000/2006
Reduce the calculation using the International Astronomical Union 2000/2006 reference system. Choose this reduction method if the reference coordinate system for the conversion is IAU-2000. This reduction method uses the P03 precession model to reduce the calculation.
Specify the year used to calculate the Universal Coordinated
Time (UTC) date. Enter a double value that is a whole number greater
than 1, such as 2013
.
Specify the month used to calculate the UTC date. From the list,
select the month from January
to December
.
Specify the day used to calculate the UTC date. From the list,
select the day from 1
to 31
.
Specify the hour used to calculate the UTC date. Enter a double
value that is a whole number from 0
to 24
.
Specify the minutes used to calculate the UTC date. Enter a
double value that is a whole number from 0
to 60
.
Specify the seconds used to calculate the UTC date. Enter a
double value that is a whole number from 0
to 60
.
Specify the time increment between the specified date and the
desired model simulation time. The block adjusts the calculated direction
cosine matrix to take into account the time increment from model simulation.
For example, selecting Day
and connecting a simulation
timer to the port means that each time increment unit is one day.
The block adjusts the calculation based on that simulation time.
This parameter corresponds to the fifth block input, the clock source.
Possible values are Day
, Hour
, Min
, Sec
,
and None
. If you select None
,
the calculated Julian date does not take into account the model simulation
time. Selecting None
removes the fifth block input.
Specify the block behavior when the block inputs are out of range.
Action | Description |
---|---|
None | No action. |
Warning | Warning in the MATLAB^{®} Command Window, model simulation continues. |
Error (default) | MATLAB returns an exception, model simulation stops. |
Select this check box to allow the following as block inputs. These inputs let you better control the conversion result. See Inputs and Outputs for a description.
X_{i} |
ΔUT1 |
ΔAT |
[xp,yp] |
[Δδψ, Δδε] or [dX,dY] |
day |
Specifies the parameter and output units.
Units | Position | Equatorial Radius | Altitude |
---|---|---|---|
| Meters | Meters | Meters |
| Feet | Feet | Feet |
This option is available only when Earth
model is set to WGS84
.
Specifies the planet model to use: Custom
or WGS84
.
Specifies the flattening of the planet. This option is only
available with Earth model set to Custom
.
Specifies the radius of the planet at its equator. This option
is only available with Earth model set to Custom
.
Specifies the reference location in latitude and longitude in degrees.
Specifies angle for converting the flat Earth x and y coordinates to north and east coordinates, respectively. An example is the angle between the vessel and the true geodetic north.
Specifies the reference height measured from the surface of the Earth to the flat Earth frame. It uses the same units as the ECI position. Estimate the reference height relative to the Earth frame.
Input | Dimension Type | Description |
---|---|---|
First | 3-by-1 element vector | X, position in ECI coordinates. |
Second (Optional) | Scalar | ΔUT1, difference between UTC
and Universal Time (UT1), in seconds, for which the function calculates
the direction cosine or transformation matrix, for example, |
Third (Optional) | Scalar | ΔAT, difference between International
Atomic Time (IAT) and UTC, in seconds, for which the function calculates
the direction cosine or transformation matrix, for example, |
Fourth (Optional) | 1-by-2 array | [xp,yp], polar
displacement of the Earth, in radians, from the motion of the Earth
crust, along the x- and y-axes,
for example, |
Fifth (Optional) | 1-by-2 array |
For historical values, see the International
Earth Rotation and Reference Systems Service website ( |
Sixth | Scalar | Time increment, for example, the Clock block. If
the Higher accuracy parameters check box is cleared
and the Time Increment parameter is a value other
than |
Output | Dimension Type | Description |
---|---|---|
First | 3-by-1 element vector | 3-by-1 element vector with the local reference coordinates azimuth (degrees), elevation (degrees), and slant range (meters). |