It is important to be able to view the lightmap UVs that are being used, and Unity has a visualization tool to help you with this. First, open the Lighting window (menu: Window > RenderingThe process of drawing graphics to the screen (or to a render texture). By default, the main camera in Unity renders its view to the screen. More info
See in Glossary > Lighting) and tick the Auto checkbox at the bottom. This ensures that your bake and precompute are up-to-date, and outputs the data that is needed to view the UVs. Wait for the process to finish (this can take some time for large or complex Scenes).
To see the UVs for the Realtime Global IlluminationA group of techniques that model both direct and indirect lighting to provide realistic lighting results. Unity has two global illumination systems that combine direct and indirect lighting.: Baked Global Illumination, and Realtime Global Illumination.
See in Glossary system:
This displays the UV layout for the real-time lightmapA pre-rendered texture that contains the effects of light sources on static objects in the scene. Lightmaps are overlaid on top of scene geometry to create the effect of lighting. More info
See in Glossary of the selected instance of this Mesh.
Multiple instances can be packed into a real-time lightmap, so some of the charts you see might actually belong to other GameObjects.
To see the UVs for the Baked Global Illumination system:
As you can see, the baked UVs are very different to the precomputed real-time UVs. This is because the requirements for baked and precomputed real-time UVs are different.