Algorithm 1. Function of the GD–Taylor method.
Input	Locations of anchors (x1, y1), (x2, y2),…, (xn, yn) Received time stamps 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	while times < max_iter do
5	d1, d2, …, dn are the distances from anchors to (x, y);
6	use (8) and (11) to calculate ${\mathsf{\delta }}_{Taylor}$ and ${\mathsf{\delta }}_{GD}$;
7	Set ${\mathsf{\delta }}_{GD-Taylor}$ to (${\mathsf{\delta }}_{Taylor}$+${\mathsf{\delta }}_{GD}$);
8	Set weight to (weight+ ${\mathsf{\delta }}_{GD-Taylor, x^2}$ + ${\mathsf{\delta }}_{GD-Taylor, y^2}$);
9	Set x to (x+ ${\mathsf{\delta }}_{GD-Taylor, x}$/(weight)1/2);
10	Set y to (y+ ${\mathsf{\delta }}_{GD-Taylor, y}$/(weight)1/2);
11	times++;
12	if ((${\mathsf{\delta }}_{GD-Taylor}$, x2+ ${\mathsf{\delta }}_{GD-Taylor}$, y2)/weight)1/2 < 0.001 then
13	break
14	end if
15	end while
16	return (x, y)