// Delta vs <v2obs>
// x y dy
0.016786	0.004639	0.002880
0.025825	0.013247	0.002400
0.036513	0.018746	0.002256
0.044704	0.021019	0.002247
0.047412	0.023126	0.002216
0.043555	0.020231	0.002043
0.032584	0.013576	0.001979
0.020110	0.007878	0.002741
0.011234	-0.001115	0.002753