Bad News for GCDB Users
Recently the BLM published an update of their GCDB data, or the section, township, range, and lot and tract data and published it to their web site. We recently took a close look at the Wyoming update to this data in shape file format. Our clients rely on this data in Wyoming as they use it to plan wells and locate leases in Wyoming’s exploration basins in addition to our industry standard version of the data from USGS topographic maps. There are several troubling aspects to the new BLM data, many of which have been problems right along. For example:
Sections, townships, lots and tracts have been physically moved from the last update, in some instances by as much as 800 feet.
The BLM GCDB Data Quality Information metadata page says that the data are topologically structured. This is not the case. We have identified more than 865 slivers in the data corresponding to gaps and overlaps within the data
The BLM Metadata page states, “The GCDB was created to provide the BLM and its public with a set of geographic foundation data that would most accurately portray the locations of PLSS corners.
These observation are concerning as the data were released without any explanation as to why the township data were moved. Moving large chunks of data by large amounts statewide creates large questions in the data consumer’s mind. I have made a point of telling clients in the past that it is absolutely critical to understand how a data set was acquired, how it was processed, and to understand what the changes mean. Without that piece of information, you are operating your exploration program in the dark.
Given the past two published versions of the data, we see little evidence to indicate that the BLM is honoring their vision for the GCDB cadastral data.
