/* boton zoom control */
#btn_zoomOut, #btn_zoomIn, #btn_zoomHome {
    background-color: white;
    position: fixed;
    color: grey;
    right: 0;
    border-radius: 50%;
    border: none;
    width: 40px;
    height: 40px;
    margin: 2px;
    font-size: 1rem;
    font-weight: 700;
    text-align: center;    
    vertical-align: center;
}
#btn_zoomIn {
    top: 80px;;
}
#btn_zoomHome {
    top: 121px;;
}
#btn_zoomOut {
    top: 162px;;
}