Topics in Module 3:

• The National Geospatial Data Clearinghouse
• Metadata Standards
• Framework, and Levels of Use of Cadastral Data
• Spatial Data Transfer Standard
• Other FGDC standards (link to the FGDC home page)
• Open GIS
• Relationship of Existing Data Sets to the Cadastral Data Content Standard

The National Geospatial Data Clearinghouse

(The information below is summarized from Clearinghouse Web pages constructed and maintained by Douglas D. Nebert, FGDC, and Chief, Spatial Data Support Unit, USGS.)

The National Geospatial Data Clearinghouse is a distributed, electronically connected network of geospatial data producers, managers, and users. The clearinghouse will allow its users to determine what geospatial data exist, find the data they need, evaluate the usefulness of the data for their applications, and obtain or order the data as economically as possible.

By Executive Order of the President, all agencies are required to document their digital spatial data and make it available to the public to encourage re-use of expensive information. The National Geospatial Data Clearinghouse is a FGDC-sponsored activity that provides a series of technical solutions to making spatial data discoverable on the Internet. The FGDC facilitates the accessibility of digital spatial information on the Internet among federal and state organizations. Using the data elements defined in the Content Standard for Digital Geospatial Metadata, governmental, non-profit, and commercial participants worldwide can make their collections of spatial information searchable and accessible on the Internet.

The clearinghouse can be described as:

• a distributed archive of information -- distributed among several nodes within an organization, but accessible to all potential users through a single point-of-entry, or gateway, managed by the FGDC
• a virtual spatial data clearinghouse to enable the rapid discovery, review, and retrieval of digital spatial data through the Internet
• a referral service to discover who has what information
• a set of information stores that use hardware, software, and telecommunications networks to provide access to information
• a distributed browseable and searchable clearinghouse of spatial data

• facilitate the construction of NSDI Clearinghouse nodes
• be an inventory of spatial data holdings
• documentation of all data sets created after January 11, 1995
• placement of descriptive information (metadata) in an on-line searchable service starting in January 1995
• on-line access to spatial data sets through the metadata

A Clearinghouse Node can be established wherever you have a collection of data, and metadata, to describe them. Smaller collections, sites which have poor or limited Internet connectivity, or sites that are unable to host the metadata and data -- but have metadata -- are invited to partner with other Clearinghouse activities within your region or discipline. The key to success is in making your metadata discoverable through search in Clearinghouse, so it matters little who actually houses and serves the metadata.

To participate in the Geospatial Data Clearinghouse Activity, a participating site must have the following ingredients in place:

• Metadata (descriptive fields) that describe a digital geospatial data set. Data elements must match fields and logic of the FGDC Content Standards for Digital Geospatial Metadata.
• Computer hardware to store the indexed metadata in various forms, connected to the Internet.
• Z39.50 software that supports access to your metadata using the Geospatial Metadata Profile (GEO).
• Metadata Parser Software (optional). The metadata parser (mp) program supports validation and reformatting of FGDC metadata into SGML, HTML, TEXT, and DIF formats from TEXT or SGML.

[In addition to the clearinghouse there as an effort within USGS for a revision to the national atlas. This program is providing a standardized interface to geospatial search engines for web searches within the USGS. It is expected that this engine could be linked to the clearinghouse requirements for information in the FGDC Metadata format related to the FGDC data themes.]

Metadata Standards

In addition, relationships between the Cadastral Data Content Standard and the Geospatial Metadata Standard for the purpose of exchanging cadastral data in the future will be described in the Cadastral Data Transfer Profile section of Module 6.

For more information on the Metadata Standard, see the FGDC Metadata home page, and Content Standards for Digital Geospatial Metadata.

Framework, and Levels of Use of Cadastral Data

• Users of digital geospatial data, varying greatly in purpose, often have a need for a few common themes of data. Because of past lack of coordination and common approaches, organizations often cannot share data, and thus spend time and money duplicating data sets already collected by others. Duplicate data sets may exists for some regions, while for other regions there may be no data collected.
• A geospatial data framework will "provide a base on which to collect, register, or integrate information accurately."
• "The information content for the framework will include the data themes of geodetic control, digital orthoimagery, elevation, transportation, hydrography, government units, and cadastre."

In order for data sources to support NSDI and Framework as they are currently envisioned, some level of data standardization will be required. Framework data must be easily accessed and exchanged across multiple agency and organizational data stores. To support this exchange or transfer of information, the FGDC Subcommittee on Cadastral Data has initiated a modular approach to developing a physical data profile (see Module 6 ) for exchanging information. In addition, efforts have been started to develop complementary computer assisted tools to help users crosswalk and transfer existing data to the profile.

Check out the Framework website for more information on Framework.

Levels of Use. The concept levels of use was introduced and summarized in Module 2 How the Standard Was Developed. The summaries from Module 2 are repeated here, along with further detail and examples.

To understand the usefulness of cadastral data, it is convenient to divide the uses into three levels: Presentation, Analysis, and Transaction. None of these levels are mandated and none are pre-specified as framework data.

1. Presentation. This level of use of cadastral data is for displaying information in a simple and cartographically pleasing manner, and for the display of other information in reference to the Public Land Survey System. It is used primarily for georeference, with no cadastral attributes. In Minnesota, for example, a state-wide base map provides PLSS data down to the sixteenth section level. This base product is advertised as a standard for PLSS presentation. This has reduced duplication of effort by Minnesota agencies through standardized coding, attributing, and presentation. Another example of presentational use of landnet type data is being developed by the Wisconsin Department of Natural Resources (DNR). A portion of Wisconsin's statewide layer can be seen in two Oneida County townships. Still another example of presentational use of public land survey data can be seen in a Dubuque, County, Iowa PLS layer.

2. Analysis. This level of use is for GIS analysis such as generalizing and categorizing, resulting in graphic presentation of text and/or attribute databases, or generalized graphic representation of land ownership and other cadastral related information. The analysis level is a statistical sampling or generalization for transaction level information. GIS analysis might yield such examples as: all parcels with similar restrictions on use; or which are managed by one agency; or which are part of a single program. Another example could be a local tax map, a graphic display of taxable parcels linked to a taxation database. Still another analysis application could be using a Master Title Plat to observe patterns of land activity and trends, but not to convey lands or write legal activities. For an example of Analytical use of cadastral data, see the Osage County example.

3. Transaction. This level of use is the true cadastral graphic that is tied fully to the legal record used to manage cadastral level data. This is the most detailed and most accurate representation of land ownership information. It is the foundation for the analysis and presentation levels of use. The transaction level of use of cadastral data conducts transactions on real property, and manages cadastral information to support transactions, especially legal documents and records. A description of how transactional use of cadastral data may be applied in the near future is described in the Osage County example.

Much of the detail in the Cadastral Data Content Standard supports the transaction level. The analysis and transaction levels are usually the most meaningful to decision making, though presentation level (as in the Minnesota example) can be used too. In general there is increasing detail as the levels move from presentation to analysis to transaction levels.

(The above descriptions are derived from "Framework Cadastral Data" (no date) by Nancy Von Meyer, Fairview Industries, along with discussions during Cadastral Data Content Standard educational committee meetings.)

Spatial Data Transfer Standard

The development of the SDTS was led by the U.S. Geological Survey, working with academic, industrial, and federal, state, and local government users of computer mapping and GIS.

Use of the SDTS is mandatory for federal agencies, according to Federal Information Processing Standard (FIPS) Publication 173. Other agencies, such as state and local governments, and private organizations, may also use SDTS, though it is not mandatory that they do so.

OpenGIS

What OpenGIS is: "The OpenGIS Specification is a comprehensive software architecture specification that provides a standard way to represent all kinds of geodata in software and a common set of services to support distributed geoprocessing in heterogeneous environments. Programming interfaces based on this specification will enable true interoperability between applications on the desktop, and they will enable access (often but not necessarily object-based) to heterogeneous geodata and geoprocessing resources across local and wide area networks." A primary goal is "to integrate geographic information contained in heterogeneous data stores whose incompatible formats and data structures have prevented interoperability."

The OpenGIS standard is relevant to the Cadastral Data Content Standard in that "OpenGIS technology was cited by the Federal Geographic Data Committee (FGDC) in its 1994 Plan for the National Spatial Data Infrastructure (NSDI) in recognition for its potential as an enabling technology for NSDI projects."

All information and quotes in this section are derived from the OGC's online brochure.

Reviewing these examples will help familiarize you with the way cadastral data from varying agencies can all relate to the Cadastral Data Content Standard. As you read about the agency examples below, think about how your own cadastral data is being used and will be used in the future.

BLM's land and minerals records

ALP The USDA Forest Service Automated Lands Project

This ends Course Module 3. Use the links below to return to the top of this page, or to go on to Module 4, or any of the other Modules.

Links to the Course Modules: [Quick Reference] [Introduction] [Module 1: Purpose and Benefits of the Cadastral Data Content Standard] [Module 2: How the Standard Was Developed] [Module 3: Other Standards and Related Activities] [Module 4: Data Modeling Techniques, Rules and Diagram Conventions] [Module 5: Crosswalks, Translations, and Examples] [Module 6: Understanding Compliance with the Standard] [Module 7: Maintenance of the Standard] [Module 8: User and Technical Support] [County Recorder Module] [GIS Specialist Module] [Surveyor Module] [Glossary]