Traditional legal doctrine pictures land ownership in the form of a cone down to the center of the earth. This article suggests that it is desirable for the law to enable subsurface subdivision into separate, three-dimensional property units, constituting separate subjects for title and transactions. Thus the law would contribute to the public interest in recognizing the subsurface space as a separate property unit from both the functional and the planning aspects.
Before three-dimensional registration can begin, it is necessary to create an infrastructure of professional standards for three-dimensional survey for registration purposes. The creation of such standards constitutes one of the main goals of the world survey profession.
It may be assumed that there is a downward limit below which the subsurface has no effect on the surface space and vice versa. In this case, the traditional doctrine may be seriously contested by the argument that those deep levels of the earth should be defined as a collective property. However, it is not practical to establish a fixed downward limit upon ownership of subsurface space. When expropriating the subsurface, it is necessary to compensate the landowner for the consequential damage, as well as for the direct damage incurred. There is some doubt whether compensation should be paid for subsurface area that the landowner could not reasonably and practically exploit. As soon as the axiomatic impediment to three-dimensional subdivision is removed, the importance of long-term planning for subsurface use will increase.