# gsw_distance

```spherical earth distance between points in long,
lat coordinates at a given pressure```

## USAGE:

`distance = gsw_distance(long,lat,{p})`

## DESCRIPTION:

```Calculates the distance in metres between successive points in the
vectors long and lat, computed using the Haversine formula on a
spherical earth of radius 6,371 km, being the radius of a sphere having
the same volume as Earth. For a sperical Earth of radius 6,371,000 m,
one nautical mile is 1,853.2488 m, thus one degree of latitude is
111,194.93 m.
Note. Distances are probably good to better than 1% of the "true"
distance on the ellipsoidal earth.```

## INPUT:

```long  =  longitude in decimal degress                     [ 0 ... +360 ]
or [ -180 ... +180 ]
lat   =  latitude in decimal degress north               [ -90 ... +90 ]```
`OPTIONAL:`
```p     =  sea pressure ( default is 0 )                          [ dbar ]
( i.e. absolute pressure - 10.1325 dbar )```
```lat and long need to have the same dimensions, Mx1 or 1xN or MxN.
p, if provided, may have dimensions 1x1 or Mx1 or 1xN or MxN,
where lat & long are Mx1 or 1xN or MxN.```

## OUTPUT:

```distance  =  Distance between points on a spherical                [ m ]
Earth at pressure (p)
Note. The output is in m not km.```

## EXAMPLE:

```Example 1  Station 1 is at (-35, 159) & Station 2 is at (35, 220)
long = [159 220]
lat = [-35 35]```
` distance = gsw_distance(long,lat)`
` distance =`
`   1.003097465291600e+007`
```Example 2  Station 1 is at (-35, 159) & Station 2 is at (35, 220),
the pressure at  Station 1 is 200 and at Station 2 it is 1000 dbar.
long = [159 220]
lat = [-35 35]
p = [200 1000]```
```Note that the pressures are not equal, we therefore calculate the
distance between stations at the mid pressure.```
` distance = gsw_distance(long,lat,p)`
` distance =`
`  1.003066163927133e+007`
```Example 3 If the locations are entered as pairs in a column it will
calculate the distances between each pairs of stations (points).
long = [159 220; 140 200]
lat = [-35 35; 20 45]
p = [200 1000]```
` distance = gsw_distance(long,lat,p)`
` distance =`
```     1.003066163927133e+007
6.11164218568001e+006```

## AUTHOR:

```6th November, 2000 by Rich Pawlowicz               [ help@teos-10.org ]
Note. This function was extracted from Rich Pawlowicz's m_map package,
which is available from http://www.eos.ubc.ca/~rich/map.html```
```MODIFIED:
28th July, 2010 by Paul Barker and Trevor McDougall.```

## VERSION NUMBER:

`3.05 (16th February, 2015)`

## REFERENCE:

`Rich Pawlowicz's m_map package.  http://www.eos.ubc.ca/~rich/map.html`
`The software is available from http://www.TEOS-10.org`