A city is a set of coterminous spaces in which people coexist to diverse degrees. Public spaces belong to everybody, and the coexistence of all is possible under certain community-defined rules. Public space can also be recognized by opposition to private spaces, in which an owner’s right to restrict in a much larger measure the interaction levels is recognized, even if general laws are still to be applied (I.e. your property rights do not allow murder of trespassers).
Public properties, despite belonging to everyone, are not homogeneous; they have different owners (state, region, city, administrative units in the above), and distinct statutes. It is not uncommon to see legal systems dividing public property into public domains (for instance streets) and public patrimony (for instance, schools), with diverging sales possibilities. The later have property rights that are similar to those of private properties.
Urban planning defines the future limit between public domain and private domain (the rest) by drawing the plot line. This means that planning can define changes to private property in its present form.
For some centuries in many countries there have been systems to define the present configuration of private property and how they relate to public ones, with the aim to guarantee the property rights and to raise taxes related to it.
In Spain two systems (this is just an outline) coexist:
- The land cadastre, an administrative record managed by the Tax Ministry, in which all urban and rural properties are inscribed, inscription being compulsory and free of charge. Today it is a digital graphical base, used for local property taxes and income taxes. As a free access graphic base it is in growing use. Tax payers are not necessarily land owners. In 2011 it covered in urban areas 13.435.868 plots with a combined area of 1.098.77 hectares. Rural areas had 39.861.294 plots with a combined area of 47.540.978 hectares.
- The Land Property Registry, created in 1861, which is public and subject to a price. The inscription of a lot guarantees property, but as the description is to often only a text describing the relation with neighboring properties, there can be substantial differences with the Cadastre graphic bases. All conditions applying to the lot, as mortgages, are inscribed in the Registry.
So all the land plots in Spain are theretically included in the cadastre, but only a fraction is in the registry. The cadastral database is updated by entire municipalities (or by the inscription of building permits) with some regularity, and the geometry of contiguous land plots is coherente, while the registry is updated each time that an isolated owner asks for it. The cadastral taxpayer is considered secret data, but a citizen can ask the registry for data about the owner and deeds running with the land.
For an urban planner, the cadastre can give a rather good property map, but contacting the real owner can be more complex: it is possible that no one pays the local real estate taxes, and the sale of the lot could never have been inscribed in the registry, or have been inscribed in 1920… by an owner whose last trace is to have emigrated to Buenos Aires in 1930