From d54fe7c1f704a63824c5bfa0ece65245572e9b27 Mon Sep 17 00:00:00 2001 From: Joseph Hunkeler Date: Wed, 4 Mar 2015 21:21:30 -0500 Subject: Initial commit --- src/slalib/sun67.htx/node46.html | 123 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 src/slalib/sun67.htx/node46.html (limited to 'src/slalib/sun67.htx/node46.html') diff --git a/src/slalib/sun67.htx/node46.html b/src/slalib/sun67.htx/node46.html new file mode 100644 index 0000000..39a1ffd --- /dev/null +++ b/src/slalib/sun67.htx/node46.html @@ -0,0 +1,123 @@ + + + + +SLA_DBEAR - Direction Between Points on a Sphere + + + + + + + + + + + + +
+ +next + +up + +previous +
+ Next: SLA_DBJIN - Decode String to B/J Epoch (DP) +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_DAV2M - Rotation Matrix from Axial Vector +

+

+

SLA_DBEAR - Direction Between Points on a Sphere +   +

+
+
ACTION: +
Returns the bearing (position angle) of one point on a +sphere relative to another (double precision). +

CALL: +
D = sla_DBEAR (A1, B1, A2, B2) +

+

+
GIVEN: +
+
+ + + + + + + + + +
A1,B1Dspherical coordinates of one point
A2,B2Dspherical coordinates of the other point
+

+
RETURNED: +
+
+ + + + + +
sla_DBEARDbearing from first point to second
+

+
NOTES: +
+
1. +
The spherical coordinates are $[\,\alpha,\delta\,]$,$[\lambda,\phi]$ etc., in radians. +
2. +
The result is the bearing (position angle), in radians, + of point [A2,B2] as seen + from point [A1,B1]. It is in the range $\pm \pi$. The sense + is such that if [A2,B2] + is a small distance due east of [A1,B1] the result + is about $+\pi/2$. Zero is returned + if the two points are coincident. +
3. +
If either B-coordinate is outside the range $\pm\pi/2$, the + result may correspond to ``the long way round''. +
4. +
The routine sla_DPAV performs an equivalent function except + that the points are specified in the form of Cartesian unit + vectors. +
+
+ +next + +up + +previous +
+ Next: SLA_DBJIN - Decode String to B/J Epoch (DP) +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_DAV2M - Rotation Matrix from Axial Vector +

+

+

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