Road Finder

1.

form a road seed from each combination of vertical and horizontal clusters in each panel of the two seed planes (the seed is formed from one horizontal and one vertical cluster in each of the two planes; each of the four clusters have the same panel number);

2.

determine the road trajectory by fitting a straight line to the positions of the clusters;

3.

for each of the non-seed planes in the same spectrometer arm,

• project along the straight-line trajectory to the plane, and determine the position of the intersection point of the line with the plane;
• search for horizontal and vertical clusters (in the panel with the same number as the one from which the seed clusters were taken) whose centroids are within a specific distance from this intersection point;
• if there are clusters within the search window, attach the one with centroid closest to the intersection point;
• refit the trajectory, including all of the clusters attached to the road;

4.

apply cuts to eliminate ghost roads³:

• a vertex cut
• and a $\chi^2$ cut