scircle1
Small circles from center, range, and azimuth
Syntax
[lat,lon] = scircle1(lat0,lon0,rad)
[lat,lon] = scircle1(lat0,lon0,rad,az)
[lat,lon] = scircle1(lat0,lon0,rad,az,ellipsoid)
[lat,lon] = scircle1(lat0,lon0,rad,units)
[lat,lon] = scircle1(lat0,lon0,rad,az,units)
[lat,lon] = scircle1(lat0,lon0,rad,az,ellipsoid,units)
[lat,lon] = scircle1(lat0,lon0,rad,az,ellipsoid,units,npts)
[lat,lon] = scircle1(track,...)
Description
[lat,lon] = scircle1(lat0,lon0,rad) computes
small circles (on a sphere) with a center at the point lat0,lon0 and
radius rad. The inputs can be scalar or column
vectors. The input radius is in degrees of arc length on a sphere.
[lat,lon] = scircle1(lat0,lon0,rad,az) uses
the input az to define the small circle arcs computed.
The arc azimuths are measured clockwise from due north. If az is
a column vector, then the arc length is computed from due north. If az is
a two-column matrix, then the small circle arcs are computed starting
at the azimuth in the first column and ending at the azimuth in the
second column. If az = [], then a complete small
circle is computed.
[lat,lon] = scircle1(lat0,lon0,rad,az,ellipsoid) computes small circles
on the ellipsoid defined by the input ellipsoid, rather than by
assuming a sphere. ellipsoid is a referenceSphere, referenceEllipsoid, or oblateSpheroid object, or a vector of the form [semimajor_axis
eccentricity]. If the semimajor axis is non-zero, rad
is assumed to be in distance units matching the units of the semimajor axis. However, if
ellipsoid = [], or if the semimajor axis is zero, then
rad is interpreted as an angle and the small circles are computed
on a sphere as in the preceding syntax.
[lat,lon] = scircle1(lat0,lon0,rad,units),
[lat,lon] = scircle1(lat0,lon0,rad,az,units), and
[lat,lon] = scircle1(lat0,lon0,rad,az,ellipsoid,units)
are
all 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] = scircle1(lat0,lon0,rad,az,ellipsoid, uses
the scalar input units,npts)npts to determine the number of
points per small circle computed. The default value of npts is
100.
[lat,lon] = scircle1(track,...) uses track to define either a great
circle or rhumb line radius. If track =
'gc'track = 'rh',
then the circles with radii of constant rhumb line distance are computed. If you omit
track, 'gc' is assumed.
mat = scircle1(...) returns a single output
argument where mat = [lat lon]. This is useful
if a single small circle is computed.
Multiple circles can be defined from a single starting point
by providing scalar lat0,lon0 inputs and column
vectors for rad and az if desired.
Examples
Create and plot a small circle centered at (0º,0º) with a radius of 10º.
axesm('mercator','MapLatLimit',[-30 30],'MapLonLimit',[-30 30]);
[latc,longc] = scircle1(0,0,10);
plotm(latc,longc,'g')If the desired radius is known in some nonangular distance unit,
use the radius returned by the earthRadius function
as the ellipsoid input to set the range units. (Use an empty azimuth
entry to indicate a full circle.)
[latc,longc] = scircle1(0,0,550,[],earthRadius('nm'));
plotm(latc,longc,'r')For just an arc of the circle, enter an azimuth range.
[latc,longc] = scircle1(0,0,5,[-30 70]); plotm(latc,longc,'m')
