dazldr_c |

Table of contents## Proceduredazldr_c ( Derivative of AZ/EL w.r.t. rectangular ) void dazldr_c ( SpiceDouble x, SpiceDouble y, SpiceDouble z, SpiceBoolean azccw, SpiceBoolean elplsz, SpiceDouble jacobi [3][3] ) ## AbstractCompute the Jacobian matrix of the transformation from rectangular to azimuth/elevation coordinates. ## Required_ReadingNone. ## KeywordsCOORDINATES DERIVATIVES MATRIX ## Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- x I x-coordinate of point. y I y-coordinate of point. z I z-coordinate of point. azccw I Flag indicating how azimuth is measured. elplsz I Flag indicating how elevation is measured. jacobi O Matrix of partial derivatives. ## Detailed_Inputx, y, z are the rectangular coordinates of the point at which the Jacobian matrix of the map from rectangular to azimuth/elevation coordinates is desired. azccw is a flag indicating how the azimuth is measured. If `azccw' is SPICETRUE, the azimuth increases in the counterclockwise direction; otherwise it increases in the clockwise direction. elplsz is a flag indicating how the elevation is measured. If `elplsz' is SPICETRUE, the elevation increases from the XY plane toward +Z; otherwise toward -Z. ## Detailed_Outputjacobi is the matrix of partial derivatives of the transformation from rectangular to azimuth/elevation coordinates. It has the form .- -. | dr/dx dr/dy dr/dz | | daz/dx daz/dy daz/dz | | del/dx del/dy del/dz | `- -' evaluated at the input values of `x', `y', and `z'. ## ParametersNone. ## Exceptions1) If the input point is on the Z-axis ( x = 0 and y = 0 ), the Jacobian matrix is undefined and therefore, the error SPICE(POINTONZAXIS) is signaled by a routine in the call tree of this routine. ## FilesNone. ## ParticularsWhen performing vector calculations with velocities it is usually most convenient to work in rectangular coordinates. However, once the vector manipulations have been performed it is often desirable to convert the rectangular representations into azimuth/elevation coordinates to gain insights about phenomena in this coordinate system. To transform rectangular velocities to derivatives of coordinates in an azimuth/elevation coordinate system, one uses the Jacobian matrix of the transformation between the two systems. Given a state in rectangular coordinates ( x, y, z, dx, dy, dz ) the corresponding azimuth/elevation coordinate derivatives are given by the matrix equation: t | t (dr, daz, del) = jacobi| * (dx, dy, dz) |(x,y,z) This routine computes the matrix | jacobi| |(x, y, z) In the azimuth/elevation coordinate system, several conventions exist on how azimuth and elevation are measured. Using the `azccw' and `elplsz' flags, users indicate which conventions shall be used. See the descriptions of these input arguments for details. ## ExamplesThe numerical results shown for this example may differ across platforms. The results depend on the SPICE kernels used as input, the compiler and supporting libraries, and the machine specific arithmetic implementation. 1) Find the azimuth/elevation state of Venus as seen from the DSS-14 station at a given epoch. Map this state back to rectangular coordinates as a check. Task description ================ In this example, we will obtain the apparent state of Venus as seen from the DSS-14 station in the DSS-14 topocentric reference frame. We will use a station frames kernel and transform the resulting rectangular coordinates to azimuth, elevation and range and its derivatives using recazl_c and ## RestrictionsNone. ## Literature_ReferencesNone. ## Author_and_InstitutionJ. Diaz del Rio (ODC Space) ## Version-CSPICE Version 1.0.0, 07-AUG-2021 (JDR) ## Index_EntriesJacobian matrix of AZ/EL w.r.t. rectangular coordinates Rectangular to range, azimuth and elevation derivative Rectangular to range, AZ and EL velocity conversion |

Fri Dec 31 18:41:04 2021