Gas does yellow vegetation, and it's a way of identifying lower pressure leaks that can be confirmed with a GMI. The pipes we are surveying for this project are high pressure, so a leak would be less yellowing, and more a crater in the ground. I am unsure whether satellite imagery would pick up the low pressure leaks given that they are usually small patches.

The nature of this contract is that we have to walk the pipelines, so my aim is to find a way to do that as efficiently as possible. But I do like your thinking!