What is Cadastral Data and why do we need standards?
GIS cadastral data is the compilation of land records information into a continuous map of a jurisdiction, typically a county. Land records information is gathered from existing property maps, original subdivision plats, legal land descriptions, road right-of-way maps, and other reliable sources. Cadastral data is usually created to support property taxation purposes and is typically integrated with property ownership records.
Standards are important for effective communication, integration and sharing of data. These framework standards provide sufficient information to support integrating basic land parcel information across jurisdictional boundaries and answering fundamental questions for business processes that need cadastral information.
What is the basis for these Cadastral Framework Standards?
The Cadastral Sub-Committee of the Federal Geodetic Data Committee has adopted a set of “framework” standards called “Cadastral Core Data” for publication and distribution of cadastral information by cadastral producers and distributors. The Standards and Recommendations Committee of the Indiana Geographic Information Council has adapted and expanded on this standard to use as the basis for its cadastral framework standards for Indiana.
How are the Cadastral Framework Standards organized?
These cadastral framework standards are presented in four parts. The data considered “Core” are divided into two categories – “Core Geometry” and “Core Attributes.” Core Geometry is comprised of fields considered necessary to uniquely define and reflect the spatial orientation and location of a parcel. Core Attributes are those minimum attribute data considered necessary to adequately document a parcel in a GIS system. The standard also includes “Core Plus” options, and a table of suggested field types and sizes for the Core and Core Plus attribute fields.
What are Core Plus Standards?
In its framework standards, the FGDC Sub-Committee offered what it termed optional “Core Plus” attributes for parcels. This concept has also been used in this Indiana standard. Core Plus attributes are those attributes that a cadastral producer or distributor may deem desirable for inclusion as part of the cadastral information, but are not considered necessary. The Core Plus attributes in the Indiana standard are Owner-related, Improvement and Assessment/Value Information.
What are the critical issues when considering Cadastral Standards?
When considering cadastral standards, it is especially important to recognize the following:
- Cadastral map content should be detailed and complete
- Cadastral map data should be compiled and constructed using coordinate geometry and precision placement techniques whenever possible
- Attributes are as important as spatial information when used to support business decisions
- Careful consideration must be given to how cadastral data will be improved upon and updated over time
- Care should be taken to respect the privacy policies of the jurisdiction dealing with cadastral attribute information
What other information should be considered before starting to build a Cadastre?
The National Geodetic Reference System (NGRS)The National Geodetic Survey manages and coordinates the NGRS to provide for a uniform and consistent definition of coordinate system, horizontal and vertical datums and monumented points throughout the country.
OrthophotographyOrthophotography should be tied to the NGRS and have a resolution of one or two foot pixels for rural areas and 6 inch pixels or smaller for subdivided or urban areas. The orthophotography should be generated from aerial photography flown at an appropriate altitude to support the mapping of cadastral details for rural and urban areas and meet published specifications (ASPRS, USGS, FGDC). Orthophotography should be updated at a frequency of 2 to 5 years as appropriate for growth and development of the mapped area.
HydrographySufficient hydrography to support the definition of cadastral features is necessary. This will normally include meanderable bodies of water, named bodies of water, and water features that otherwise form parcel boundaries.