How to measure a diamond-shaped locator pin?

How to measure a diamond-shaped locator pin?

This might be a basic question, but I’m struggling with it.

How would you approach measuring a 2-way locator "diamond-shaped" pin, like the one in the image? I need to report (GD&T) the position of that pin as well as the longer size (length) , so I assume I need to "create" a feature (of size) for it.

Thanks in advance for your help!