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# scircleg

Small circle defined via mouse input

## Syntax

h = scircleg(ncirc)
h = scircleg(ncirc,npts)
h = scircleg(ncirc,linestyle)
h = scircleg(ncirc,PropertyName,PropertyValue,...)
[lat,lon] = scircleg(ncirc,npts,...)
h = scircleg(track,ncirc,...)

## Description

h = scircleg(ncirc) brings forward the current map axes and waits for the user to make (2 * ncirc) mouse clicks. The output h is a vector of handles for the ncirc small circles, which are then displayed.

h = scircleg(ncirc,npts) specifies the number of plotting points to be used for each small circle. npts is 100 by default.

h = scircleg(ncirc,linestyle) specifies the line style for the displayed small circles, where linestyle is any line style string recognized by the standard MATLAB® function line.

h = scircleg(ncirc,PropertyName,PropertyValue,...) allows property name/property value pairs to be set, where PropertyName and PropertyValue are recognized by the line function.

[lat,lon] = scircleg(ncirc,npts,...) returns the coordinates of the plotted points rather than the handles of the small circles. Successive circles are stored in separate columns of lat and lon.

h = scircleg(track,ncirc,...) specifies the logic with which ranges are calculated. If the string track is 'gc' (the default), great circle distance is used. If track is 'rh', rhumb line distance is used.

This function is used to define small circles for display using mouse clicks. For each circle, two clicks are required: one to mark the center of the circle and one to mark any point on the circle itself, thereby defining the radius.

## Background

A small circle is the locus of all points an equal surface distance from a given center. For true small circles, this distance is always calculated in a great circle sense; however, the scircleg function allows a locus to be calculated using distances in a rhumb line sense as well. You can modify the circle after creation by shift+clicking it. The circle is then in edit mode, during which you can change the size and position by dragging control points, or by entering values into a control panel. Shift+clicking again exits edit mode.