function fig_geo_q3_coverage()
%FIG_GEO_Q3_COVERAGE  问题三：七个 1000 m 接收盘覆盖区域 Ω。

    S = fig_style();
    D = load_data(S, 'geo_q3');
    H = geom_helpers();
    fig = figure('Color', 'w', 'Visible', 'off');
    ax = axes(fig);
    hold(ax, 'on');

    hd = gobjects(0);
    for i = 1:size(D.stations, 1)
        hd = H.disk(ax, D.stations(i, :), D.r_eff, pick_color(S, 'success'), 0.18, '-');
    end
    hw = H.circle(ax, [0 0], D.omega_r, pick_color(S, 'primary'), 1.2, '-');
    hs = plot(ax, D.stations(:, 1), D.stations(:, 2), 'o', 'MarkerSize', 6, ...
              'MarkerFaceColor', pick_color(S, 'accent'), 'MarkerEdgeColor', 'none');
    hx = H.marker(ax, D.worst, 'k', 8, false);
    hold(ax, 'off');
    axis(ax, 'equal');
    xlim(ax, [-D.half, D.half]);
    ylim(ax, [-D.half, D.half]);
    xlabel(ax, 'x / m');
    ylabel(ax, 'y / m');
    legend(ax, [hw, hd(1), hs, hx], D.legend, 'Location', 'southoutside', ...
           'Orientation', 'horizontal');

    fig_save(fig, S, 'geo-q3-seven-point-coverage.png');
end