# track2

Geographic tracks from starting and ending points

## Syntax

```[lat,lon] = track2(lat1,lon1,lat2,lon2) [lat,lon] = track2(lat1,lon1,lat2,lon2,ellipsoid) [lat,lon] = track2(lat1,lon1,lat2,lon2,units) [lat,lon] = track2(lat1,lon1,lat2,lon2,ellipsoid,units) [lat,lon] = track2(lat1,lon1,lat2,lon2,ellipsoid,units,npts) [lat,lon] = track2(track,...) mat = track2(...) ```

## Description

`[lat,lon] = track2(lat1,lon1,lat2,lon2)` computes great circle tracks on a sphere starting at the point `lat1,lon1` and ending at `lat2,lon2`. The inputs can be scalar or column vectors.

`[lat,lon] = track2(lat1,lon1,lat2,lon2,ellipsoid)` computes the great circle track on the ellipsoid defined by the input `ellipsoid`. `ellipsoid` is a `referenceSphere`, `referenceEllipsoid`, or `oblateSpheroid` object, or a vector of the form ```[semimajor_axis eccentricity]```. If `ellipsoid = []`, a sphere is assumed.

`[lat,lon] = track2(lat1,lon1,lat2,lon2,units)` and
`[lat,lon] = track2(lat1,lon1,lat2,lon2,ellipsoid,units)` are both valid calling forms, which use the input units to define the angle units of the inputs and outputs. If you omit `units`, `'degrees'` is assumed.

`[lat,lon] = track2(lat1,lon1,lat2,lon2,ellipsoid,units,npts)` uses the scalar input `npts` to determine the number of points per track computed. The default value of `npts` is 100.

`[lat,lon] = track2(track,...)` uses the track to define either a great circle or a rhumb line track. If ```track = 'gc'```, then great circle tracks are computed. If ```track = 'rh'```, then rhumb line tracks are computed. If you omit track, `'gc'` is assumed.

`mat = track2(...)` returns a single output argument where `mat = [lat lon]`. This is useful if a single track is computed. Multiple tracks can be defined from a single starting point by providing scalar inputs for `lat1,lon1` and column vectors for `lat2,lon2`.

## Examples

```% Set up the axes. axesm('mercator','MapLatLimit',[30 50],'MapLonLimit',[-40 40]) % Calculate the great circle track. [lattrkgc,lontrkgc] = track2(40,-35,40,35); % Calculate the rhumb line track. [lattrkrh,lontrkrh] = track2('rh',40,-35,40,35); % Plot both tracks. plotm(lattrkgc,lontrkgc,'g') plotm(lattrkrh,lontrkrh,'r')``` collapse all

### Track Lines

A path along the surface of the Earth connecting two points is a track. Two types of track lines are of interest geographically, great circles and rhumb lines. Great circles represent the shortest possible path between two points. Rhumb lines are paths with constant angular headings. They are not, in general, the shortest path between two points. 