ECI Position to AER

Convert Earth-centered inertial (ECI) coordinates to azimuth coordinates

  • Library:
  • Aerospace Blockset / Utilities / Axes Transformations

Description

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.

Ports

Input

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Position, specified as a 3-by-1 element vector, in ECI coordinates.

Data Types: double

Difference between UTC and Universal Time (UT1) in seconds, specified as a scalar, for which the block calculates the direction cosine or transformation matrix.

Example: 0.234

Dependencies

To enable this port, select Higher accuracy parameters.

Data Types: double

Difference between International Atomic Time (IAT) and UTC, specified as a scalar, in seconds, for which the function calculates the direction cosine or transformation matrix.

Example: 32

Dependencies

This port is disabled if the Higher accuracy parameters check box is cleared.

Data Types: double

Polar displacement of Earth, specified as a 1-by-2 array, in radians, from the motion of the Earth crust, along the x-axis and y-axis.

Example: [-0.0682e-5 0.1616e-5]

Dependencies

To enable this port, select Higher accuracy parameters.

Data Types: double

Adjustment based on reduction method, specified as 1-by-2 array. The name of the port depends on the setting of the Reduction parameter:

  • If the reduction method is IAU-2000/2006, this input is the adjustment to the location of the Celestial Intermediate Pole (CIP), specified in radians. This location ([dX,dY]) is along the x-axis and y-axis, for example, [-0.2530e-6 -0.0188e-6].

  • If the reduction method is IAU-76/FK5, this input is the adjustment to the longitude ([Δδψ, Δδε]), specified in radians.

For historical values, see the International Earth Rotation and Reference Systems Service website (https://www.iers.org) and navigate to the Earth Orientation Data Data/Products page.

Example: [-0.2530e-6 -0.0188e-6]

Dependencies

To enable this port, select Higher accuracy parameters.

Data Types: double

Time increment source, specified as a scalar, such as the Clock block.

Dependencies

  • The port name and time increment depend on the Time Increment parameter.

    Time Increment ValuePort Name

    Day

    day

    Hour

    hour

    Min

    min

    Sec

    sec

    None

    No port

  • To disable this port, set the Time Increment parameter to None.

Data Types: double

Output

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Local reference coordinates azimuth (degrees), elevation (degrees), and slant range (meters), specified as a 3-by-1 element vector.

Data Types: double

Parameters

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Reduction method to convert the coordinates. Method can be one of:

  • 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.

    Note

    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.

Programmatic Use

Block Parameter: red
Type: character vector
Values: 'IAU-2000/2006' | 'IAU-76/FK5'
Default: 'IAU-2000/2006'

Year to calculate the Universal Coordinated Time (UTC) date. Enter a double value that is a whole number greater than 1, such as 2014.

Programmatic Use

Block Parameter: year
Type: character vector
Values: double, whole number, greater than 1
Default: '2013'

Month to calculate the UTC date.

Programmatic Use

Block Parameter: month
Type: character vector
Values: 'January' | 'February' | 'March' | 'April' | 'May' | 'June' | 'July' | 'August' | 'September' | 'October' | 'November' | 'December'
Default: 'January'

Day to calculate the UTC date.

Programmatic Use

Block Parameter: day
Type: character vector
Values: '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' | '10' | '11' | '12' | '13' | '14' | '15' | '16' | '17' | '18' | '19' | '20' | '21' | '22' | '23' | '24' | '25' | '26' | '27' | '28' | '29' | '30' | '31'
Default: '1'

Hour to calculate the UTC date. Enter a double value that is a whole number, from 0 to 24.

Programmatic Use

Block Parameter: hour
Type: character vector
Values: double, whole number, 0 to 24
Default: '0'

Minutes to calculate the UTC date. Enter a double value that is a whole number, from 0 to 60.

Programmatic Use

Block Parameter: min
Type: character vector
Values: double, whole number, 0 to 60
Default: '0'

Seconds to calculate the UTC date. Enter a double value that is a whole number, from 0 to 60.

Programmatic Use

Block Parameter: sec
Type: character vector
Values: double, whole number, 0 to 60
Default: '0'

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 and the block adjusts its calculation based on that simulation time.

This parameter corresponds to the time increment input, the clock source.

If you select None, the calculated Julian date does not take into account the model simulation time.

Programmatic Use

Block Parameter: deltaT
Type: character vector
Values: 'None' | 'Day' | 'Hour' | 'Min' | 'Sec'
Default: 'Day'

Specify the block behavior when the block inputs are out of range.

ActionDescription
None No action.
Warning Warning in the MATLAB® Command Window, model simulation continues.
Error (default) MATLAB returns an exception, model simulation stops.

Programmatic Use

Block Parameter: errorflag
Type: character vector
Values: 'None' | 'Warning' | 'Error'
Default: 'Error'

Select this check box to allow the following as block inputs. These inputs let you better control the conversion result. See Input for a description.

  • Δ UT1

  • Δ AT

  • [ xp , yp ]

  • [Δδψ, Δδε] or [d X ,d Y ]

Programmatic Use

Block Parameter: extraparamflag
Type: character vector
Values: 'on' | 'off'
Default: 'on'

Specifies the parameter and output units.

Units

Position

Equatorial Radius

Altitude

Metric (MKS)

Meters

Meters

Meters

English

Feet

Feet

Feet

Dependencies

To enable this option, set Earth model to WGS84.

Programmatic Use

Block Parameter: eunits
Type: character vector
Values: 'Metric (MKS)' | 'English'
Default: 'Metric (MKS)'

Earth model to use, Custom or Earth (WGS84).

Programmatic Use

Block Parameter: earthmodel
Type: character vector
Values: 'Earth (WGS84)' | 'Custom'
Default: 'Earth (WGS84)'

Flattening of the planet, specified as a double scalar.

Dependencies

To enable this parameter, set Earth model to Custom.

Programmatic Use

Block Parameter: flat
Type: character vector
Values: double scalar
Default: 1/298.257223563

Radius of the planet at its equator.

Dependencies

To enable this parameter, set Earth model to Custom.

Programmatic Use

Block Parameter: eqradius
Type: character vector
Values: double scalar
Default: 6378137

Reference location in latitude and longitude, specified as 2-by-1 vector, in degrees.

Programmatic Use

Block Parameter: latlon0
Type: character vector
Values: 2-by-1 vector
Default: [0 0]

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.

Programmatic Use

Block Parameter: psi0
Type: character vector
Values: double scalar
Default: 0

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.

Programmatic Use

Block Parameter: href
Type: character vector
Values: double scalar
Default: 0

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Introduced in R2015a