Algorithm 1 Function GD-Taylor()
Input	Locations of anchors (x1, y1), (x2, y2), …, (xn, yn)
	Received timestamps t1, t2, …, tn
	Maximal iteration time max_iter
	Initial location (xinit, yinit)
Output	Estimated location of tag (xt, yt)
1	Calculate d21, d31, …, dn1 by multiplying light speed and
	time resolution to (t2 − t1), (t3 − t1), …, (tn − t1);
2	Set weight to 10−10;
3	Set (x, y) to (xinit, yinit);
4	whiletimes < max_iter do
5	d1, d2, …, dn are the distances from anchors to (x, y);
6	use (8) and (11) to calculate δTaylor and δGD;
7	Set δGD-Taylor to (δTaylor + δGD);
8	Set weight to (weight + δGD-Taylor, x2 + δGD-Taylor, y2);
9	Set x to (x + δGD-Taylor, x /(weight)1/2);
10	Set y to (y + δGD-Taylor, y /(weight)1/2);
11	times++;
12	if ((δGD-Taylor, x2 + δGD-Taylor, y2)/weight)1/2 < 0.001 then
13	break
14	endif
15	endwhile
16	return (x, y)