The default planet is the size of Earth. Imported heightmaps from image formats that do not have embedded scaling information (e.g. bmp, jpg, png) are scaled with 1 pixel = 1 meter. You can adjust this with Heightfield Adjust nodes, assuming you are loading your images through heightfield load nodes and not as Image Maps for displacement. If they are Image Maps you can just scale them in the Image Map shader.
- Oshyan