You now know the boundaries and width of your scent trail. Face upwind and walk back into the scent trail and progress upwind, occasionally veering to the right and left to keep tabs on the trail boundaries. If you lose the trail and you are angling to the right, turn left until you pick it back up, and vice versa. The wider the track, the farther away the source. Vegetation, rocks, and landforms in or near the scent trail can modify it, either spreading, narrowing, or diffusing it.
Air temperature is next in importance, as warmer air holds more moisture.
I come across, just for the experience. I remember one particular time when a visiting friend asked if I would demonstrate scent tracking. A porcupine's scent was strong, but we couldn't follow it for more than twenty paces without losing it, and it didn't seem to be coming from any clear direction. Rather than become frustrated, I got excited, realizing I was being gifted another dimension of scent tracking. I radiated out in all directions to define the perimeter of the scent trail.