Normally the flow of mana was balanced. It had a direction and if Walker used his senses, he could track it. This was the case for many mages. As long as they had the proper affinity or skills, they could sense their mana and follow it. This was even how magical trackers could use their mana to find what they were after.
Right now though, the wind mana that Walker was sensing was flowing against the air currents above him in the air. The way that he could tell that it wasn't two opposing air currents was simple. There was nothing to cause the air to flow differently. No massive mountain to stop the air nor any canyon to greatly cause a change.
This was a very open place before entering some forests and other areas that would not change the air currents so drastically. Therefore, the proper method of solving this issue was to follow the problem overall. And with his true mana sense, that was easier than ever.
Your gift is the motivation for my creation. Give me more motivation!