next up previous
Next: SLA_DRANGE - Put Angle into Range
Up: SUBPROGRAM SPECIFICATIONS
Previous: SLA_DR2AF - Radians to Deg,Min,Sec,Frac

SLA_DR2TF - Radians to Hour,Min,Sec,Frac   

ACTION:
Convert an angle in radians to hours, minutes, seconds, fraction (double precision).

CALL:
CALL sla_DR2TF (NDP, ANGLE, SIGN, IHMSF)

GIVEN:

NDP I number of decimal places of seconds
ANGLE D angle in radians

RETURNED:

SIGN C `+' or `-'
IHMSF I(4) hours, minutes, seconds, fraction

NOTES:
1.
NDP less than zero is interpreted as zero.
2.
The largest useful value for NDP is determined by the size of ANGLE, the format of DOUBLE PRECISION floating-point numbers on the target machine, and the risk of overflowing IHMSF(4). For example, on a VAX computer, for ANGLE up to $2\pi$, the available floating-point precision corresponds roughly to NDP=12. However, the practical limit is NDP=9, set by the capacity of the 32-bit integer IHMSF(4).
3.
The absolute value of ANGLE may exceed $2\pi$. In cases where it does not, it is up to the caller to test for and handle the case where ANGLE is very nearly $2\pi$ and rounds up to 24 hours, by testing for IHMSF(1)=24 and setting IHMSF(1-4) to zero.


next up previous
Next: SLA_DRANGE - Put Angle into Range
Up: SUBPROGRAM SPECIFICATIONS
Previous: SLA_DR2AF - Radians to Deg,Min,Sec,Frac

SLALIB --- Positional Astronomy Library
Starlink User Note 67
P. T. Wallace
12 October 1999
E-mail:ptw@star.rl.ac.uk