cspice_nplnpt

 Abstract I/O Examples Particulars Required Reading Version Index_Entries
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```

#### Abstract

```
CSPICE_NPLNPT calculates the location on a defined line
nearest to a specified point, then determines the distance
between the two points.

For important details concerning this module's function, please refer to
the CSPICE routine nplnpt_c.

```

#### I/O

```
Given:

linpt    a double precision 3-vector.

lindir   a double precision 3-vector.

are, respectively, a point and a direction vector that define
a line. The line is the set of vectors

linept   +   t * linedr

where t is any real number.

point    a double precision 3-vector defining a position
in space.

the call:

cspice_nplnpt, linpt, lindir, point, pnear, dist

returns:

pnear   a double precision 3-vector identifying the nearest
point on the input line to the input 'point'.

dist    the scalar double precision distance between the
input line and input point.

```

#### Examples

```
Any numerical results shown for this example may differ between
platforms as the results depend on the SPICE kernels used as input
and the machine specific arithmetic implementation.

;;
;; Define a point on a line, a direction for the line, and
;; an arbitrary point in space.
;;
linept = [  1.d, 2.d,  3.d ]
linedr = [  0.d, 1.d,  1.d ]
point  = [ -6.d, 9.d, 10.d ]

;;
;; Calculate the location on the line nearest the point
;; and the distance between the location and the defined
;; point.
;;
cspice_nplnpt, linept, linedr, point, pnear, dist
print, pnear
print, dist

IDL outputs for pnear:

1.0000000   9.0000000   10.000000

IDL outputs for dist:

7.0000000

```

#### Particulars

```
For every line L and point P, there is a unique closest point
on L to P.  Call this closest point C.  It is always true that
P - C  is perpendicular to L, and the length of P - C is called
the "distance" between P and L.

```

```
ICY.REQ

```

#### Version

```
-Icy Version 1.0.1, 13-JUN-2011, EDW (JPL)

Edits to I/O and Particulars sections so as to parallel Mice version.

-Icy Version 1.0.0, 16-JUN-2003, EDW (JPL)

```

#### Index_Entries

```
distance between point and line
nearest point on line to point

```
`Wed Apr  5 17:58:02 2017`