Documentation

lla2eci

Convert geodetic latitude, longitude, altitude (LLA) coordinates to Earth-centered inertial (ECI) coordinates

Description

example

position = lla2eci(lla,utc) converts geodetic latitude, longitude, altitude (LLA) coordinates to Earth-centered inertial (ECI) position coordinates as an M-by-3 array. The conversion is based on the Universal Coordinated Time (UTC) you specify.

example

position = lla2eci(lla,utc,reduction) converts geodetic latitude, longitude, altitude (LLA) coordinates to Earth-centered inertial (ECI) position coordinates as an M-by-3 array. The conversion is based on the specified reduction method and the Universal Coordinated Time (UTC) you specify.

position = lla2eci(lla,utc,reduction,deltaAT) uses the difference between International Atomic Time and UTC that you specify as deltaAT to calculate the ECI coordinates.

position = lla2eci(lla,utc,reduction,deltaAT,deltaUT1) uses the difference between UTC and Universal Time (UT1), which you specify as deltaUT1, in the calculation.

position = lla2eci(lla,utc,reduction,deltaAT,deltaUT1,polarmotion) uses the polar displacement, polarmotion, in the calculation.

position = lla2eci(lla,utc,reduction,deltaAT,deltaUT1,polarmotion,Name,Value) uses additional options specified by one or more Name,Value pair arguments.

Examples

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Convert the position to ECI coordinates from LLA coordinates 6 degrees north, 75 degrees west, and 1000 meters altitude at 01/17/2010 10:20:36 UTC.

position = lla2eci([6 -75 1000],[2010 1 17 10 20 36])
position=

1.0e+06 *

-6.0744   -1.8289    0.6685

Convert the position to ECI coordinates from LLA coordinates 55 deg south, 75 deg west, and 500 meters altitude at 01/12/2000 4:52:12.4 UTC. Specify all arguments, including optional ones such as polar motion.

position = lla2eci([-55 -75 500],[2000 1 12 4 52 12.4],...
'IAU-76/FK5',32,0.234,[-0.0682e-5 0.1616e-5],...
'dNutation',[-0.2530e-6 -0.0188e-6],...
'flattening',1/290,'RE',60000)
position=

1.0e+04 *

-1.1358    3.2875   -4.9333

Input Arguments

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Latitude, longitude, altitude (LLA) coordinates as M-by-3 array of geodetic coordinates, in degrees, degrees, and meters, respectively. Latitude and longitude values can be any value. However, latitude values of +90 and -90 may return unexpected values because of singularity at the poles.

Universal Coordinated Time (UTC), in the order year, month, day, hour, minutes, and seconds, for which the function calculates the conversion, specified as one of the following.

• For the year value, enter a double value that is a whole number greater than 1, such as 2013.

• For the month value, enter a double value that is a whole number greater than 0, within the range 1 to 12.

• For the hour value, enter a double value that is a whole number greater than 0, within the range 1 to 24.

• For the hour value, enter a double value that is a whole number greater than 0, within the range 1 to 60.

• For the minute and second values, enter a double value that is a whole number greater than 0, within the range 1 to 60.

Specify these values in one of the following formats:

• 1-by-6 array

Specify a 1-row-by-6-column array of UTC values.

• M-by-6 matrix

Specify an M-by-6 array of UTC values, where M is the number of transformation matrices to calculate. Each row corresponds to one set of UTC values.

This is a one row-by-6 column array of UTC values.

Example: [2000 1 12 4 52 12.4]

This is an M-by-6 array of UTC values, where M is 2.

Example: [2000 1 12 4 52 12.4;2010 6 5 7 22 0]

Data Types: double

Reduction method to calculate the coordinate conversion, specified as one of the following:

• 'IAU-76/FK5'

Reduce the calculation using the International Astronomical Union (IAU)-76/Fifth Fundamental Catalogue (FK5) (IAU-76/FK5) reference system. Choose this reduction method if the reference coordinate system for the conversion is FK5. You can use the 'dNutation' Name,Value pair with this reduction.

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, lla2eci performs a coordinate conversion that is not orthogonal because of the polar motion approximation.

• 'IAU-2000/2006'

Reduce the calculation using the International Astronomical Union (IAU)-2000/2005 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. You can use the 'dCIP' Name,Value pair with this reduction.

Difference between International Atomic Time (IAT) and UTC, in seconds, for which the function calculates the coordinate conversion.

• scalar

Specify one difference-time value to calculate one direction cosine or transformation matrix.

• one-dimensional array

Specify a one-dimensional array with M elements, where M is the number of ECI coordinates. Each row corresponds to one set of ECI coordinates.

Specify 32 seconds as the difference between IAT and UTC.

Example: 32

Data Types: double

Difference between UTC and Universal Time (UT1), in seconds, for which the function calculates the coordinate conversion.

• scalar

Specify one difference-time value to calculate ECI coordinates.

• one-dimensional array

Specify a one-dimensional array with M elements of difference time values, where M is the number of ECI coordinates. Each row corresponds to one set of ECI coordinates.

Specify 0.234 seconds as the difference between UTC and UT1.

Example: 0.234

Data Types: double

Polar displacement of the Earth, in radians, from the motion of the Earth crust, along the x- and y-axes.

• 1-by-2 array

Specify a 1-by-2 array of the polar displacement values to convert one ECI coordinate.

• M-by-2 array

Specify an M-by-2 array of polar displacement values, where M is the number of ECI coordinates to convert. Each row corresponds to one set of UTC values.

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

Data Types: double

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: 'dNutation',[-0.2530e-6 -0.0188e-6]

Adjustment to the longitude (dDeltaPsi) and obliquity (dDeltaEpsilon), specified in radians, as the comma-separated pair consisting of dNutation and an M-by-2 array. You can use this Name,Value pair with the IAU-76/FK5 reduction.

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.

• M-by-2 array

Specify M-by-2 array of adjustment values, where M is the number of LLA coordinates to be converted. Each row corresponds to one set of longitude and obliquity values.

Data Types: double

Adjustment to the location of the Celestial Intermediate Pole (CIP), in radians, specified as the comma-separated pair consisting of dCIP and an M-by-2 array. This location (dDeltaX, dDeltaY) is along the x- and y- axes. You can use this argument with the IAU-200/2006 reduction. By default, this function assumes an M-by-2 array of zeroes.

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.

• M-by-2 array

Specify M-by-2 array of location adjustment values, where M is the number of LLA coordinates to be converted. Each row corresponds to one set of dDeltaX and dDeltaY values.

Example: 'dcip',[-0.2530e-6 -0.0188e-6]

Data Types: double

Custom ellipsoid planet defined by flattening.

Example: 1/290

Data Types: double

Custom planet ellipsoid radius, in meters.

Example: 60000

Data Types: double 