Understanding Land databases

Land administration is a major area of concern in many jurisdictions around the world. What seems as a fairly straightforward domain actually involves many datasets that do not integrate well with each other.

Types of databases

These include the following:
1. A Title or ownership database - A Title/ Ownership database is a record of ownership of land or property. In most areas, it maintains a reference to the piece of land through some unique identifier, a legal description of the title which may refer to a lot number in a specific subdivision plan, as well as a record of ownership and transfers. In case, the land organization maintains a separate document library, it will refer to the document and the filing number, or a book and a page number.

2. A Cadastral database - A Cadastral maintains a record of the geometry of land. A cadastral database may maintain its own numbering system for identifying a unique piece of land. A cadastral database typically records data in terms of plans. Each plan has a boundary denoting the study area as well as control points that are established for accuracy. Each plan will then have a set of surveyed lines and points (also called line points) as they are used to establish the accuracy of the lines.
Finally, resulting from these are parcel boundaries which are actually derived from the survey lines.

3. An Assessment or Valuation database - An assessment database keeps track of properties from a valuation perspective. Valuation or assessment maps are prepared in jurisdictions where taxes are collected based on uses and improvements done to a piece of land. The argument being that a five star hotel built on a property should be charged more than a piece of land that is being farmed. Property taxes are also levied so that people don't simply buy land for speculative purposes and leave it vacant but are forced to put it to some economic use. Based on this need, assessment maps are prepared that are then used by taxation authorities to track changes in usage and improvements done to piece of land.

Other information in primary datasets

Typically sales history is tied to the title database. Structures history is tied to the valuation database as these indicate improvements in land. The original subdivision planning is tied to the cadastral database as these include lot and parcel numbers.

Tied to all the above datasets are documents that include all sorts of records and plans around land transactions. Since all these databases do not have a consistent view of a parcel/ property, most land administration organizations maintain cross reference table such that as long as the user had one piece of information, other datasets can be accessed.