Chris Wiita, a cadastral surveyor, BLM Alaska. (photo by John Taivalkoski, BLM)
From Chains to Lasers and Global Satellites
By Robert Casias
From the earliest days of our nation’s history, the job of a federal land surveyor has been to identify the boundaries of the federal estate. By measuring both the direction (bearing) and distance of boundary lines that construct the network of the Public Land Survey System (PLSS), surveyors have created the legal structure for maintaining title ownership of land in the West and large parts of the eastern United States.
The art of measurement has significantly evolved over the past 200 years. Surveyors working at the turn of the 19th century were dragging a 66-foot chain across the landscape and sighting the sun and stars to determine their direction and distance measurements. With the advent of laser technology, surveyors working in the 1970s found themselves freed of their chains and able to measure up to 3 miles at a time with a “Total Station” and a single electronic distance measurement (EDM). Laser technology allowed surveyors to make highly accurate distance measurements over large expanses in very little time. Although this technology significantly improved efficiencies, there were many surveyors who continued, for some time, to take their chains to the field to validate the measurements reported by their new EDM instruments.
In the late 1980s, the military began releasing an unencrypted signal from their constellation of global positioning system (GPS) satellites, and very soon, GPS technology allowed private and federal land surveyors to access continuous, worldwide, three-dimensional positioning information that today allows us to locate geographic positions on the ground to within a centimeter of accuracy. In 1980, the National Research Council released a report to Congress with a far-reaching vision of how cadastral data should exist in digital form. The “Need for a Multipurpose Cadastre” report stated that there should be a single, comprehensive, multipurpose cadastre that would be readily available at the parcel level for the entire nation. Two outcomes of this report brought BLM cadastral surveys into the spotlight, as PLSS data was a foundational element of the proposed national cadastre.
A BLM surveyor using GPS technology in California. (BLM)
The first outcome of the report was that Congress identified the BLM’s cadastral survey program as the responsible party for collecting all PLSS geometries in a digital format. This effort was termed the Geographic Coordinate Data Base (GCDB) Project, and it transformed all of those measurements formerly found only on the official survey plats into a digital representation. The GCDB has become an invaluable tool to BLM land managers, who now widely use geographic information systems (GIS) to make decisions regarding the management of public lands.
The second outcome of the report was that the Office of Management and Budget extended the idea of common “multipurpose” mapping data by identifying seven separate themes that would be provided free of charge by the BLM to the public. These themes, known as the National Spatial Data Infrastructure framework, include cadastral survey boundaries, vegetation, transportation, terrain topology, and other national datasets. The Federal Geographic Data Committee (FGDC) was formed in 1990 to develop standards enabling these themes to be incorporated into a national dataset. The Department of the Interior (DOI) assumed responsibility for the cadastral framework along with several other themes. A Presidential order in 1994 specifically placed BLM in charge of data standards for the cadastral framework theme.
The BLM’s cadastral survey program has led the FGDC Cadastral Data Subcommittee and has already developed three kinds of standards: data content, transfer, and publication standards. While standards were evolving, the work of collecting GCDB data was continuous.
Since the 1970s, the BLM has collected many land records other than survey data. These records were combined with the GCDB into a GIS-based software the BLM built known as the Automated Land and Mineral Records System. Although there were merits to the system, it failed in staged operational testing and was subsequently abandoned. However, the test results noted the success of the spatial display of parcels, all of which were based on the GCDB portrayal of the PLSS.
In 1999, Congress encouraged the Forest Service and the BLM to combine their efforts into a single land information management system that would be useful to all other land management agencies and could be used by local jurisdictions such as states and counties. This system was known as the National Integrated Land System, which was the first digital multipurpose cadastre within the DOI. The vision was to have a coast-to-coast parcel dataset, with sources housed throughout the country, that would use GIS technology to automatically stitch the data together from these sources without the user needing to do anything more than ask for it.
|Arizona surveyors in 1910. (BLM)|
The BLM continues its efforts to integrate both the spatial component and the tabular data that define the scope of its work on the public lands. We truly have come a long way in this field . . . from chains to lasers and global satellites.
Bob Casias is the deputy state director for cadastral survey and geographic sciences in BLM’s New Mexico State Office. He has been acting deputy state director for business resources, chief cadastral surveyor, and a land surveyor for the BLM in New Mexico.