5 SUMMARY OF CALLS

The basic trigonometrical and numerical facilities are supplied in both single and double precision versions. Most of the more esoteric position and time routines use double precision arguments only, even in cases where single precision would normally be adequate in practice. Certain routines with modest accuracy objectives are supplied in single precision versions only. In the calling sequences which follow, no attempt has been made to distinguish between single and double precision argument names, and frequently the same name is used on different occasions to mean different things. However, none of the routines uses a mixture of single and double precision arguments; each routine is either wholly single precision or wholly double precision.

In the classified list, below, subroutine subprograms are those whose names and argument lists are preceded by ‘CALL’, whereas function subprograms are those beginning ‘R=’ (when the result is REAL) or ‘D=’ (when the result is DOUBLE PRECISION).

The list is, of course, merely for quick reference; inexperienced users must refer to the detailed specifications given later. In particular, don’t guess whether arguments are single or double precision; the result could be a program that happens to works on one sort of machine but not on another.

String Decoding

CALL sla_INTIN (STRING, NSTRT, IRESLT, JFLAG)
Convert free-format string into integer

CALL sla_FLOTIN (STRING, NSTRT, RESLT, JFLAG)
CALL sla_DFLTIN (STRING, NSTRT, DRESLT, JFLAG)
Convert free-format string into floating-point number

CALL sla_AFIN (STRING, NSTRT, RESLT, JFLAG)
CALL sla_DAFIN (STRING, NSTRT, DRESLT, JFLAG)
Convert free-format string from deg,arcmin,arcsec to radians

Sexagesimal Conversions

CALL sla_CTF2D (IHOUR, IMIN, SEC, DAYS, J)
CALL sla_DTF2D (IHOUR, IMIN, SEC, DAYS, J)
Hours, minutes, seconds to days

CALL sla_CD2TF (NDP, DAYS, SIGN, IHMSF)
CALL sla_DD2TF (NDP, DAYS, SIGN, IHMSF)
Days to hours, minutes, seconds

CALL sla_CTF2R (IHOUR, IMIN, SEC, RAD, J)
CALL sla_DTF2R (IHOUR, IMIN, SEC, RAD, J)
Hours, minutes, seconds to radians

CALL sla_CR2TF (NDP, ANGLE, SIGN, IHMSF)
CALL sla_DR2TF (NDP, ANGLE, SIGN, IHMSF)
Radians to hours, minutes, seconds

CALL sla_CAF2R (IDEG, IAMIN, ASEC, RAD, J)
CALL sla_DAF2R (IDEG, IAMIN, ASEC, RAD, J)
Degrees, arcminutes, arcseconds to radians

CALL sla_CR2AF (NDP, ANGLE, SIGN, IDMSF)
CALL sla_DR2AF (NDP, ANGLE, SIGN, IDMSF)
Radians to degrees, arcminutes, arcseconds

Angles, Vectors and Rotation Matrices

R = sla_RANGE (ANGLE)
D = sla_DRANGE (ANGLE)
Normalize angle into range ±π

R = sla_RANORM (ANGLE)
D = sla_DRANRM (ANGLE)
Normalize angle into range 0 −2π

CALL sla_CS2C (A, B, V)
CALL sla_DCS2C (A, B, V)
Spherical coordinates to [x, y, z]

CALL sla_CC2S (V, A, B)
CALL sla_DCC2S (V, A, B)
[x, y, z] to spherical coordinates

R = sla_VDV (VA, VB)
D = sla_DVDV (VA, VB)
Scalar product of two 3-vectors

CALL sla_VXV (VA, VB, VC)
CALL sla_DVXV (VA, VB, VC)
Vector product of two 3-vectors

CALL sla_VN (V, UV, VM)
CALL sla_DVN (V, UV, VM)
Normalize a 3-vector also giving the modulus

R = sla_SEP (A1, B1, A2, B2)
D = sla_DSEP (A1, B1, A2, B2)
Angle between two points on a sphere

R = sla_SEPV (V1, V2)
D = sla_DSEPV (V1, V2)
Angle between two [x, y, z] vectors

R = sla_BEAR (A1, B1, A2, B2)
D = sla_DBEAR (A1, B1, A2, B2)
Direction of one point on a sphere seen from another

R = sla_PAV (V1, V2)
D = sla_DPAV (V1, V2)
Position-angle of one [x, y, z] with respect to another

CALL sla_EULER (ORDER, PHI, THETA, PSI, RMAT)
CALL sla_DEULER (ORDER, PHI, THETA, PSI, RMAT)
Form rotation matrix from three Euler angles

CALL sla_AV2M (AXVEC, RMAT)
CALL sla_DAV2M (AXVEC, RMAT)
Form rotation matrix from axial vector

CALL sla_M2AV (RMAT, AXVEC)
CALL sla_DM2AV (RMAT, AXVEC)
Determine axial vector from rotation matrix

CALL sla_MXV (RM, VA, VB)
CALL sla_DMXV (DM, VA, VB)
Rotate vector forwards

CALL sla_IMXV (RM, VA, VB)
CALL sla_DIMXV (DM, VA, VB)
Rotate vector backwards

CALL sla_MXM (A, B, C)
CALL sla_DMXM (A, B, C)
Product of two 3x3 matrices

CALL sla_CS2C6 (A, B, R, AD, BD, RD, V)
CALL sla_DS2C6 (A, B, R, AD, BD, RD, V)
Conversion of position and velocity in spherical coordinates to Cartesian coordinates

CALL sla_CC62S (V, A, B, R, AD, BD, RD)
CALL sla_DC62S (V, A, B, R, AD, BD, RD)
Conversion of position and velocity in Cartesian coordinates to spherical coordinates

Calendars

CALL sla_CLDJ (IY, IM, ID, DJM, J)
Gregorian Calendar to Modified Julian Date

CALL sla_CALDJ (IY, IM, ID, DJM, J)
Gregorian Calendar to Modified Julian Date, permitting century default

CALL sla_DJCAL (NDP, DJM, IYMDF, J)
Modified Julian Date to Gregorian Calendar, in a form convenient for formatted output

CALL sla_DJCL (DJM, IY, IM, ID, FD, J)
Modified Julian Date to Gregorian Year, Month, Day, Fraction

CALL sla_CALYD (IY, IM, ID, NY, ND, J)
Calendar to year and day in year, permitting century default

CALL sla_CLYD (IY, IM, ID, NY, ND, J)
Calendar to year and day in year

D = sla_EPB (DATE)
Modified Julian Date to Besselian Epoch

D = sla_EPB2D (EPB)
Besselian Epoch to Modified Julian Date

D = sla_EPJ (DATE)
Modified Julian Date to Julian Epoch

D = sla_EPJ2D (EPJ)
Julian Epoch to Modified Julian Date

Time Scales

D = sla_GMST (UT1)
Conversion from Universal Time to sidereal time

D = sla_GMSTA (DATE, UT1)
Conversion from Universal Time to sidereal time, rounding errors minimized

D = sla_EQEQX (DATE)
Equation of the equinoxes

D = sla_DAT (DJU)
Offset of Atomic Time from Coordinated Universal Time: TAI−UTC

D = sla_DT (EPOCH)
Approximate offset between dynamical time and universal time

D = sla_DTT (DJU)
Offset of Terrestrial Time from Coordinated Universal Time: TT−UTC

D = sla_RCC (TDB, UT1, WL, U, V)
Relativistic clock correction: TDB−TT

Precession and Nutation

CALL sla_NUT (DATE, RMATN)
Nutation matrix

CALL sla_NUTC (DATE, DPSI, DEPS, EPS0)
Longitude and obliquity components of nutation, and mean obliquity

CALL sla_NUTC80 (DATE, DPSI, DEPS, EPS0)
Longitude and obliquity components of nutation, and mean obliquity, IAU 1980

CALL sla_PREC (EP0, EP1, RMATP)
Precession matrix (IAU)

CALL sla_PRECL (EP0, EP1, RMATP)
Precession matrix (suitable for long periods)

CALL sla_PRENUT (EPOCH, DATE, RMATPN)
Combined precession-nutation matrix

CALL sla_PREBN (BEP0, BEP1, RMATP)
Precession matrix, old system

CALL sla_PRECES (SYSTEM, EP0, EP1, RA, DC)
Precession, in either the old or the new system

Proper Motion

CALL sla_PM (R0, D0, PR, PD, PX, RV, EP0, EP1, R1, D1)
Adjust for proper motion

FK4/FK5/Hipparcos Conversions

CALL sla_FK425 (R1950, D1950, DR1950, DD1950, P1950, V1950, R2000, D2000, DR2000, DD2000, P2000, V2000)
Convert B1950.0 FK4 star data to J2000.0 FK5

CALL sla_FK45Z (R1950, D1950, EPOCH, R2000, D2000)
Convert B1950.0 FK4 position to J2000.0 FK5 assuming zero FK5 proper motion and no parallax

CALL sla_FK524 (R2000, D2000, DR2000, DD2000, P2000, V2000, R1950, D1950, DR1950, DD1950, P1950, V1950)
Convert J2000.0 FK5 star data to B1950.0 FK4

CALL sla_FK54Z (R2000, D2000, BEPOCH, R1950, D1950, DR1950, DD1950)
Convert J2000.0 FK5 position to B1950.0 FK4 assuming zero FK5 proper motion and no parallax

CALL sla_FK52H (R5, D5, DR5, DD5, RH, DH, DRH, DDH)
Convert J2000.0 FK5 star data to Hipparcos

CALL sla_FK5HZ (R5, D5, EPOCH, RH, DH )
Convert J2000.0 FK5 position to Hipparcos assuming zero Hipparcos proper motion

CALL sla_H2FK5 (RH, DH, DRH, DDH, R5, D5, DR5, DD5)
Convert Hipparcos star data to J2000.0 FK5

CALL sla_HFK5Z (RH, DH, EPOCH, R5, D5, DR5, DD5)
Convert Hipparcos position to J2000.0 FK5 assuming zero Hipparcos proper motion

CALL sla_DBJIN (STRING, NSTRT, DRESLT, J1, J2)
Like sla_DFLTIN but with extensions to accept leading ‘B’ and ‘J’

CALL sla_KBJ (JB, E, K, J)
Select epoch prefix ‘B’ or ‘J’

D = sla_EPCO (K0, K, E)
Convert an epoch into the appropriate form – ‘B’ or ‘J’

Elliptic Aberration

CALL sla_ETRMS (EP, EV)
E-terms

CALL sla_SUBET (RC, DC, EQ, RM, DM)
Remove the E-terms

CALL sla_ADDET (RM, DM, EQ, RC, DC)
Add the E-terms

Geographical and Geocentric Coordinates

CALL sla_OBS (NUMBER, ID, NAME, WLONG, PHI, HEIGHT)
Interrogate list of observatory parameters

CALL sla_GEOC (P, H, R, Z)
Convert geodetic position to geocentric

CALL sla_POLMO (ELONGM, PHIM, XP, YP, ELONG, PHI, DAZ)
Polar motion

CALL sla_PVOBS (P, H, STL, PV)
Position and velocity of observatory

Apparent and Observed Place

CALL sla_MAP (RM, DM, PR, PD, PX, RV, EQ, DATE, RA, DA)
Mean place to geocentric apparent place

CALL sla_MAPPA (EQ, DATE, AMPRMS)
Precompute mean to apparent parameters

CALL sla_MAPQK (RM, DM, PR, PD, PX, RV, AMPRMS, RA, DA)
Mean to apparent using precomputed parameters

CALL sla_MAPQKZ (RM, DM, AMPRMS, RA, DA)
Mean to apparent using precomputed parameters, for zero proper motion, parallax and radial velocity

CALL sla_AMP (RA, DA, DATE, EQ, RM, DM)
Geocentric apparent place to mean place

CALL sla_AMPQK (RA, DA, AMPRMS, RM, DM)
Apparent to mean using precomputed parameters

CALL sla_AOP (RAP, DAP, UTC, DUT, ELONGM, PHIM, HM, XP, YP, TDK, PMB, RH, WL, TLR, AOB, ZOB, HOB, DOB, ROB)
Apparent place to observed place

CALL sla_AOPPA (UTC, DUT, ELONGM, PHIM, HM, XP, YP, TDK, PMB, RH, WL, TLR, AOPRMS)
Precompute apparent to observed parameters

CALL sla_AOPPAT (UTC, AOPRMS)
Update sidereal time in apparent to observed parameters

CALL sla_AOPQK (RAP, DAP, AOPRMS, AOB, ZOB, HOB, DOB, ROB)
Apparent to observed using precomputed parameters

CALL sla_OAP (TYPE, OB1, OB2, UTC, DUT, ELONGM, PHIM, HM, XP, YP, TDK, PMB, RH, WL, TLR, RAP, DAP)
Observed to apparent

CALL sla_OAPQK (TYPE, OB1, OB2, AOPRMS, RA, DA)
Observed to apparent using precomputed parameters

Azimuth and Elevation

CALL sla_ALTAZ (HA, DEC, PHI, AZ, AZD, AZDD, EL, ELD, ELDD, PA, PAD, PADD)
Positions, velocities etc. for an altazimuth mount

CALL sla_E2H (HA, DEC, PHI, AZ, EL)
CALL sla_DE2H (HA, DEC, PHI, AZ, EL)
[h, δ] to [Az, El]

CALL sla_H2E (AZ, EL, PHI, HA, DEC)
CALL sla_DH2E (AZ, EL, PHI, HA, DEC)
[Az, El] to [h, δ]

CALL sla_PDA2H (P, D, A, H1, J1, H2, J2)
Hour Angle corresponding to a given azimuth

CALL sla_PDQ2H (P, D, Q, H1, J1, H2, J2)
Hour Angle corresponding to a given parallactic angle

D = sla_PA (HA, DEC, PHI)
[h, δ] to parallactic angle

D = sla_ZD (HA, DEC, PHI)
[h, δ] to zenith distance

Refraction and Air Mass

CALL sla_REFRO (ZOBS, HM, TDK, PMB, RH, WL, PHI, TLR, EPS, REF)
Change in zenith distance due to refraction

CALL sla_REFCO (HM, TDK, PMB, RH, WL, PHI, TLR, EPS, REFA, REFB)
Constants for simple refraction model (accurate)

CALL sla_REFCOQ (TDK, PMB, RH, WL, REFA, REFB)
Constants for simple refraction model (fast)

CALL sla_ATMDSP ( TDK, PMB, RH, WL1, REFA1, REFB1, WL2, REFA2, REFB2 )
Adjust refraction constants for colour

CALL sla_REFZ (ZU, REFA, REFB, ZR)
Unrefracted to refracted ZD, simple model

CALL sla_REFV (VU, REFA, REFB, VR)
Unrefracted to refracted [Az, El] vector, simple model

D = sla_AIRMAS (ZD)
Air mass

Ecliptic Coordinates

CALL sla_ECMAT (DATE, RMAT)
Equatorial to ecliptic rotation matrix

CALL sla_EQECL (DR, DD, DATE, DL, DB)
J2000.0 ‘FK5’ to ecliptic coordinates

CALL sla_ECLEQ (DL, DB, DATE, DR, DD)
Ecliptic coordinates to J2000.0 ‘FK5’

Galactic Coordinates

CALL sla_EG50 (DR, DD, DL, DB)
B1950.0 ‘FK4’ to galactic

CALL sla_GE50 (DL, DB, DR, DD)
Galactic to B1950.0 ‘FK4’

CALL sla_EQGAL (DR, DD, DL, DB)
J2000.0 ‘FK5’ to galactic

CALL sla_GALEQ (DL, DB, DR, DD)
Galactic to J2000.0 ‘FK5’

Supergalactic Coordinates

CALL sla_GALSUP (DL, DB, DSL, DSB)
Galactic to supergalactic

CALL sla_SUPGAL (DSL, DSB, DL, DB)
Supergalactic to galactic

Ephemerides

CALL sla_DMOON (DATE, PV)
Approximate geocentric position and velocity of the Moon

CALL sla_EARTH (IY, ID, FD, PV)
Approximate heliocentric position and velocity of the Earth

CALL sla_EPV (DATE, DPH, DVH, DPB, DVB )
Heliocentric and barycentric position and velocity of the Earth

CALL sla_EVP (DATE, DEQX, DVB, DPB, DVH, DPH)
Barycentric and heliocentric velocity and position of the Earth

CALL sla_MOON (IY, ID, FD, PV)
Approximate geocentric position and velocity of the Moon

CALL sla_PLANET (DATE, NP, PV, JSTAT)
Approximate heliocentric position and velocity of a planet

CALL sla_RDPLAN (DATE, NP, ELONG, PHI, RA, DEC, DIAM)
Approximate topocentric apparent place of a planet

CALL sla_PLANEL (DATE, JFORM, EPOCH, ORBINC, ANODE, PERIH, AORQ, E, AORL, DM, PV, JSTAT)
Heliocentric position and velocity of a planet, asteroid or comet, starting from orbital elements

CALL sla_PLANTE (DATE, ELONG, PHI, JFORM, EPOCH, ORBINC, ANODE, PERIH, AORQ, E, AORL, DM, RA, DEC, R, JSTAT)
Topocentric apparent place of a Solar-System object whose heliocentric orbital elements are known

CALL sla_PLANTU (DATE, ELONG, PHI, U, RA, DEC, R, JSTAT)
Topocentric apparent place of a Solar-System object whose heliocentric universal orbital elements are known

CALL sla_PV2EL (PV, DATE, PMASS, JFORMR, JFORM, EPOCH, ORBINC, ANODE, PERIH, AORQ, E, AORL, DM, JSTAT)
Orbital elements of a planet from instantaneous position and velocity

CALL sla_PERTEL (JFORM, DATE0, DATE1, EPOCH0, ORBI0, ANODE0, PERIH0, AORQ0, E0, AM0, EPOCH1, ORBI1, ANODE1, PERIH1, AORQ1, E1, AM1, JSTAT)
Update elements by applying perturbations

CALL sla_EL2UE (DATE, JFORM, EPOCH, ORBINC, ANODE, PERIH, AORQ, E, AORL, DM, U, JSTAT)
Transform conventional elements to universal elements

CALL sla_UE2EL (U, JFORMR, JFORM, EPOCH, ORBINC, ANODE, PERIH, AORQ, E, AORL, DM, JSTAT)
Transform universal elements to conventional elements

CALL sla_PV2UE (PV, DATE, PMASS, U, JSTAT)
Package a position and velocity for use as universal elements

CALL sla_UE2PV (DATE, U, PV, JSTAT)
Extract the position and velocity from universal elements

CALL sla_PERTUE (DATE, U, JSTAT)
Update universal elements by applying perturbations

R = sla_RVEROT (PHI, RA, DA, ST)
Velocity component due to rotation of the Earth

CALL sla_ECOR (RM, DM, IY, ID, FD, RV, TL)
Components of velocity and light time due to Earth orbital motion

R = sla_RVLSRD (R2000, D2000)
Velocity component due to solar motion wrt dynamical LSR

R = sla_RVLSRK (R2000, D2000)
Velocity component due to solar motion wrt kinematical LSR

R = sla_RVGALC (R2000, D2000)
Velocity component due to rotation of the Galaxy

R = sla_RVLG (R2000, D2000)
Velocity component due to rotation and translation of the Galaxy, relative to the mean motion of the local group

Astrometry

CALL sla_S2TP (RA, DEC, RAZ, DECZ, XI, ETA, J)
CALL sla_DS2TP (RA, DEC, RAZ, DECZ, XI, ETA, J)
Transform spherical coordinates into tangent plane

CALL sla_V2TP (V, V0, XI, ETA, J)
CALL sla_DV2TP (V, V0, XI, ETA, J)
Transform [x, y, z] into tangent plane coordinates

CALL sla_DTP2S (XI, ETA, RAZ, DECZ, RA, DEC)
CALL sla_TP2S (XI, ETA, RAZ, DECZ, RA, DEC)
Transform tangent plane coordinates into spherical coordinates

CALL sla_DTP2V (XI, ETA, V0, V)
CALL sla_TP2V (XI, ETA, V0, V)
Transform tangent plane coordinates into [x, y, z]

CALL sla_DTPS2C (XI, ETA, RA, DEC, RAZ1, DECZ1, RAZ2, DECZ2, N)
CALL sla_TPS2C (XI, ETA, RA, DEC, RAZ1, DECZ1, RAZ2, DECZ2, N)
Get plate centre from star [α, δ] and tangent plane coordinates

CALL sla_DTPV2C (XI, ETA, V, V01, V02, N)
CALL sla_TPV2C (XI, ETA, V, V01, V02, N)
Get plate centre from star [x, y, z] and tangent plane coordinates

CALL sla_PCD (DISCO, X, Y)
Apply pincushion/barrel distortion

CALL sla_UNPCD (DISCO, X, Y)
Remove pincushion/barrel distortion

CALL sla_FITXY (ITYPE, NP, XYE, XYM, COEFFS, J)
Fit a linear model to relate two sets of [x, y] coordinates

CALL sla_PXY (NP, XYE, XYM, COEFFS, XYP, XRMS, YRMS, RRMS)
Compute predicted coordinates and residuals

CALL sla_INVF (FWDS, BKWDS, J)
Invert a linear model

CALL sla_XY2XY (X1, Y1, COEFFS, X2, Y2)
Transform one [x, y]

CALL sla_DCMPF (COEFFS, XZ, YZ, XS, YS, PERP, ORIENT)
Decompose a linear fit into scales etc.

Numerical Methods

CALL sla_COMBN (NSEL, NCAND, LIST, J)
Next combination (subset from a specified number of items)

CALL sla_PERMUT (N, ISTATE, IORDER, J)
Next permutation of a specified number of items

CALL sla_SMAT (N, A, Y, D, JF, IW)
CALL sla_DMAT (N, A, Y, D, JF, IW)
Matrix inversion and solution of simultaneous equations

CALL sla_SVD (M, N, MP, NP, A, W, V, WORK, JSTAT)
Singular value decomposition of a matrix

CALL sla_SVDSOL (M, N, MP, NP, B, U, W, V, WORK, X)
Solution from given vector plus SVD

CALL sla_SVDCOV (N, NP, NC, W, V, WORK, CVM)
Covariance matrix from SVD

R = sla_RANDOM (SEED)
Generate pseudo-random real number in the range 0 ≤ x < 1

R = sla_GRESID (S)
Generate pseudo-random normal deviate ( ≡ ‘Gaussian residual’)

Real-time

CALL sla_WAIT (DELAY)
Interval wait