function preloadTimelineNav() {
    var imgPath = "../images/timeline/";

    date_1_on = new Image();
    date_1_on.src = imgPath + "hdr_t2_date_1_on.jpg";
    date_1_off = new Image();
    date_1_off.src = imgPath + "hdr_t2_date_1_off.jpg";

    date_2_on = new Image();
    date_2_on.src = imgPath + "hdr_t3_date_2_on.jpg";
    date_2_off = new Image();
    date_2_off.src = imgPath + "hdr_t3_date_2_off.jpg";

    date_3_on = new Image();
    date_3_on.src = imgPath + "hdr_t4_date_3_on.jpg";
    date_3_off = new Image();
    date_3_off.src = imgPath + "hdr_t4_date_3_off.jpg";

    date_4_on = new Image();
    date_4_on.src = imgPath + "hdr_t5_date_4_on.jpg";
    date_4_off = new Image();
    date_4_off.src = imgPath + "hdr_t5_date_4_off.jpg";

    date_6_on = new Image();
    date_6_on.src = imgPath + "hdr_t1_date_6_on.jpg";
    date_6_off = new Image();
    date_6_off.src = imgPath + "hdr_t1_date_6_off.jpg";

    marking_1_on = new Image();
    marking_1_on.src = imgPath + "marking_typ_on.gif";
    marking_1_off = new Image();
    marking_1_off.src = imgPath + "marking_typ_off.gif";

    marking_2_on = new Image();
    marking_2_on.src = imgPath + "marking_typ_on.gif";
    marking_2_off = new Image();
    marking_2_off.src = imgPath + "marking_typ_off.gif";

    marking_3_on = new Image();
    marking_3_on.src = imgPath + "marking_typ_on.gif";
    marking_3_off = new Image();
    marking_3_off.src = imgPath + "marking_typ_off.gif";

    marking_4_on = new Image();
    marking_4_on.src = imgPath + "marking_typ_on.gif";
    marking_4_off = new Image();
    marking_4_off.src = imgPath + "marking_typ_off.gif";

    marking_6_on = new Image();
    marking_6_on.src = imgPath + "marking_typ_on.gif";
    marking_6_off = new Image();
    marking_6_off.src = imgPath + "marking_typ_off.gif";

    tb_1_on = new Image();
    tb_1_on.src = imgPath + "marking_t_b_on.gif";
    tb_1_off = new Image();
    tb_1_off.src = imgPath + "marking_t_b_off.gif";

    tb_2_on = new Image();
    tb_2_on.src = imgPath + "marking_t_b_on.gif";
    tb_2_off = new Image();
    tb_2_off.src = imgPath + "marking_t_b_off.gif";

    tb_3_on = new Image();
    tb_3_on.src = imgPath + "marking_t_b_on.gif";
    tb_3_off = new Image();
    tb_3_off.src = imgPath + "marking_t_b_off.gif";

    tb_4_on = new Image();
    tb_4_on.src = imgPath + "marking_t_b_on.gif";
    tb_4_off = new Image();
    tb_4_off.src = imgPath + "marking_t_b_off.gif";

    tb_b1_on = new Image();
    tb_b1_on.src = imgPath + "marking_t1_b1_on.gif";
    tb_b1_off = new Image();
    tb_b1_off.src = imgPath + "marking_t1_b1_off.gif";

    tb_b2_on = new Image();
    tb_b2_on.src = imgPath + "marking_t1_b2_on.gif";
    tb_b2_off = new Image();
    tb_b2_off.src = imgPath + "marking_t1_b2_off.gif";

    tb_6_on = new Image();
    tb_6_on.src = imgPath + "marking_t1_b6_on.gif";
    tb_6_off = new Image();
    tb_6_off.src = imgPath + "marking_t1_b6_off.gif";
}

preloadTimelineNav();