When the United States Bureau of Land Management (BLM) completed the initial collection of the Public Land Survey System (PLSS) dataset, they realized they needed a solution that would easily support updates to PLSS Cadastral National Spatial Data Infrastructure (CadNSDI) data; could be used by states, local governments, and all federal land agencies; and be a commercially supported product. Esri’s parcel fabric — a dataset for the storage, maintenance, and editing of parcels — has widely been regarded as a viable solution for maintaining measurement accuracy and bringing uniformity to the maintenance of cadastral datasets. Today, the BLM Cadastral Survey has fully adopted the parcel fabric to maintain PLSS data.
Laying the Groundwork
Starting in the 1980s, the BLM began collecting and indexing PLSS data to support automated land management, including geographic information system (GIS) technology. At that time, there were no commercially available products that would allow users to enter a complete PLSS township dataset, add control points, support the BLM’s basis of bearing, and apply adjustments that would generate a precise latitude and longitude for every corner. To rectify this, the BLM turned to employee William Ball to develop a program based on some earlier work Ball had done with offshore computations. The culmination of that work was the PLSS Coordinate Computational System (PCCS), which was used extensively by BLM cadastral surveyors throughout the ‘80s.
Building on the PCCS, the BLM contracted with the University of Maine to develop a customized least squares analysis program to determine the most accurate set of coordinates of all PLSS corners within surveyed areas. This would meet the specialized needs for computing and automated adjustment across large land areas, producing coordinate values for all corners along with an error estimate. Called Geographic Measurement Management (GMM), that program was used to collect the data of entire states, one township at a time, with the added features of regional adjustments to match PLSS boundaries in large township blocks.
This system was adequate for many years, but with changing technology and new opportunities to interoperate with Esri mapping software, the Federal Geographic Data Committee (FGDC) Cadastral Subcommittee developed documentation to standardize the publication of cadastral data in 2008. Derived from the FGDC Cadastral Data Content Standard, it contained the domains of values, attributes, and features that were common language in GIS. Attributes and features were subsequently protocoled to facilitate migration from flat files and maintain vertical integration with geodatabases. (That standard can be found at the FGDC Subcommittee’s outreach page.)
In 2010, the BLM — in consultation with Premier Data Services and Fairview Industries — began an intensive process of converting all western states with nearly complete PLSS coverage from GMM files into PLSS CadNSDI standard datasets. This process took almost a whole year and generated nearly 30 gigabytes of standardized, state edge-matched PLSS datasets.
Montana and Nevada Go First
In 2013, the BLM reviewed and tested many commercially available software products, including various configurations and combinations thereof. Concurrently with that analysis, the State of Montana assumed the stewardship of its PLSS CadNSDI data that also included federally managed lands. Unlike many states, Montana’s statewide parcel management relies on PLSS data for vertical integration of parcel and PLSS data. With that amount of data to oversee and edit, officials at the Montana State Library concluded that they’d need the Esri parcel fabric workflow to sustainably manage that data. By 2014, Montana became the first state to commit to loading its entire PLSS dataset into the fabric.
With more than four million polygons in one fabric, concern about performance proliferated at the library — in particular, some at BLM were doubtful that that many polygons could even be successfully loaded. The BLM and Montana began meticulous testing of the tools for PLSS adjustment and output to the PLSS CadNSDI format, addressing, one at a time, the expected hiccups and glitches that accompany the loading of such a large dataset.
Although the trial and error from that testing laid the groundwork for smoother integration for states today, planning remains essential before plunging into the fabric in order to reap maximal benefits. State GIS Coordinator for the Montana State Library Stu Kirkpatrick explains:
“State management of CadNSDI provides multiple advantages but should not be undertaken lightly without forethought — preparing the data is still essential.” says Kirkpatrick. “Now, because we’re stewards of the vertically integrated data tied to the PLSS, we can inform our users when changes occur and when they need to update other data tied to the PLSS.”
In recognition of its groundbreaking work, Montana earned a SAG Award at the 2015 Esri User Conference.
Following the success in Montana, the Nevada State Office was chosen as the full-scale test bed for the BLM. Thanks to Montana’s pioneering efforts, many parts of the process, such as loading the dataset, went smoothly for Nevada. Additional tools and scripts were deployed by Esri and tested by both Montana and Nevada. It was also critical to be able to update the published data set, as many GIS professionals in the BLM, as well as other federal agencies and states and the private sector, have come to rely on that content.
The Road Ahead
The BLM still has some remaining initial collection to complete. There are some areas in both California and Colorado that have a higher degree of complexity, such as townships with many mineral surveys, and an area of Alaska that hasn’t been surveyed or collected (there are also some areas in the eastern United States with federal interests that most likely will be further densified and updated).
Going forward, the BLM created a Change Management Board to facilitate the update process and create a collaborative environment ensuring that all stakeholder needs will be met. Continued maintenance will focus on making changes in areas with added control and new surveys (as opposed to the large area adjustments that were part of the initial collection).
With proven workflows and established procedures, the BLM now has the ability to provide very accurate updates to the PLSS CadNSDI in a timely manner.
“By adopting a commercially supported package that’s compliant with national and federal standards, we’ve built a solid foundation for the future for the BLM,” says Don Buhler, National Cadastral Director, BLM.
For more information on Montana’s transition, visit the Montana Geographic Information Clearinghouse.