A National Parcel Polygon Service — Part 2
A Nation of Parcels
The national parcel polygon service is a modest effort with achievable goals. We must prove we can assemble and maintain this data. That it can be a national and public resource. We can overcome institutional barriers combining data from multiple data stewards and sources.
Who provides this data?
The Data Steward is the primary data provider for parcel data. These are typically the local jurisdiction, a town, a city, a county and in some cases a state agency. The parcel data is often tax parcels, collected to support the records in the real estate tax system. In some cases, the parcel data are ownership parcels, including non-taxable lands. Much less common are parcel data sets that include all the lands in jurisdiction from roadways to water to more traditional parcels.
For the modest starting efforts, the national parcel polygon service does not specify which parcels are provided. It is whatever the Data Steward maintains as a regular part of business.
The Data Aggregator is an Authoritative Source. Typically, these are states but are also regional agencies within a state. Aggregated data is provided state-by-state, that is no multi-state aggregated data set have been identified in the US. The state aggregators use the data steward data sets and compile them into a single data set.
Some state aggregators use extract-transform-load routines to build statewide standardized attribution. Typically, there are fewer attributes in the state aggregated data. Data stewards may use different attribute name sand may have different values for coded domains that the state standardizes in the ETL process. The state aggregator may add information such as FIPS codes. New Mexico is an example of this approach. Some states provide the Data Steward with a specified standard and tools to build the extracted data set. North Carolina is an example of this approach. Other states assemble the local data with no standardization. In these cases, the data maybe kept as individual county files. Colorado is an example of this approach. A few states maintain the local data or keep the local data in a statewide data system. Montana is an example of this approach.
The common thread is the parcel data aggregator uses data as provided by the data steward and is an authoritative data set.
In states where no parcel data are available, third party aggregated data from Loveland Technologies is used as the fill in that completes national coverage. The figure below illustrates the data source concept.
Link Back to Source
The national parcel polygon service is a very thin modest effort, providing polygons and identifiers with links to more data aggregators who can then provide links to data stewards. Establishing this stacked hierarchical approach assures the connection to authoritative data and provides users access to the most detailed and currently available data.
What Could it Look Like?
The presentation and symbology is being explored, but the link could look as shown below. The parcels are should across data steward and data aggregator boundaries. Clicking on a parcel or selecting a set of parcels exposes the information on the data source.
The availability of local data steward download sites is indicated on the county in this graphic. But symbology and labeling are in development.
There are plans for an annual web form emailed to data aggregators to maintain the content on data aggregator source.
So Let’s Do This
We also must understand the costs, resources, and commitments necessary to provide and maintain such a service. This will take public and private resources and partnerships. Parcel providers at all levels of government must be a part of the solution.