def land_to_index(num):
    """
    This function returns the (ilat,ilon) from land sequential number.
    """
    #This is the last column
    if num%720 == 0:
        j = 719
        i = num/720 - 1
    #normal columns
    else:
        j = num%720 - 1
        i = num/720
    return (i,j)