Function gmtplot_get_local_scale

src/gmt_plot.c:4871–4881

}

GMT_LOCAL double gmtplot_get_local_scale (struct GMT_CTRL *GMT, double lon0, double lat0, double length, double azimuth) {
	/* Determine the local scale at lon0,lat in the direction azimuth using a test distance length in degrees.
	 * The scale returned can be used to convert a map distance in inch to great circle degrees.
	 * This is approximate only. */

	double tlon, tlat, x0, y0, x1, y1;
	gmtlib_get_point_from_r_az (GMT, lon0, lat0, length, azimuth, &tlon, &tlat);	/* Arbitrary 2nd point near (lon0,lat0) in the azimuth direction */
	gmt_geo_to_xy (GMT, lon0, lat0, &x0, &y0);	/* Get map position in inches for (lon0,lat0) */
	gmt_geo_to_xy (GMT, tlon, tlat, &x1, &y1);	/* Get map position in inches for close point */
	return (length / hypot (x1 - x0, y1 - y0));	/* This scales a length in inches to degrees, approximately */
}

GMT_LOCAL void gmtplot_circle_pen_poly (struct GMT_CTRL *GMT, double *A, double *B, bool longway, double rot, struct GMT_PEN *pen, struct GMT_SYMBOL *S, struct GMT_CIRCLE *C, double scale) {
	/* Given vectors A and B, return a small circle polygon path sampled every step that approximates a pen of given width