The red lines are veins. The smaller red dots on the vein indicator mean that the data ended sharply, and likely indicates that the vein hits the surface there. If no small red dot appears on the ends of the vein indicators then the data faded out gradually. Large red dots alone are usually seen in water ways, but may be a vertical vein as seen from above. These indicate probable dredging and panning locations. The large red dots on usually at the center of vein intersections is "highest reading" in our map data.