def split_line_segment(lng1, lat1, lng2, lat2, max_section_length):
    # Split line segment defined by (x1, y1, x2, y2) into a set of points 
    # (x,y,displacement) spaced less than max_section_length apart
    
    if lng1==lng2 and lat1==lat2:
        yield [lng1, lat1, 0]
        yield [lng2, lat2, 0]
        return
    
    street_len = vincenty(lat1, lng1, lat2, lng2)
    n_sections = int(street_len/max_section_length)+1
    
    geolen = ((lat2-lat1)**2 + (lng2-lng1)**2)**0.5
    section_len = geolen/n_sections
    street_vector = (lng1-lng2, lat2-lat1)
    unit_vector = [x/geolen for x in street_vector]
    
    for i in range(n_sections+1):
        vec = [x*section_len*i for x in unit_vector]
        vec = [lng1+vec[0], lat1+vec[1], (street_len/n_sections)*i]
        yield vec
dataset/ETHPy150Open bmander/graphserver/pygs/graphserver/ext/ned/elevation/elevation.py/split_line_segment/swapped operands of `-`