Area of Interest
The boundary drawn around the ground being researched, such as a list of townships and sections or a mapped polygon, that sets which records are pulled.
Detailed Definition
An area of interest (AOI) is the boundary drawn around the ground being researched. It sets which mining claim records, land status records, and mineral data are pulled and which are left out. The term is common in GIS and land work; it has no legal definition.
BLM's advice
BLM's brochure "Mining Claims and Sites on Federal Lands" recommends it directly: "Rather than looking randomly through the records for lands open to location, it is better to restrict the search to a specific area of interest." It notes that USGS topographic maps "provide the legal description (meridian, township, range, section) of such lands," and advises checking "maps, BLM master title plats, mining claim records, and files" at the BLM office responsible for the land.
Defining an AOI by the PLSS
Federal land records are organized by the Public Land Survey System. BLM's "Specifications for Descriptions of Land" (2017) describes the township as "the nominal 6-mile-square area" that is "subdivided into 36 'sections,' with each section being nominally 1 mile square, 640 acres." Many records follow that grid:
- Master title plats show "current land status for a specified township" (BLM Land Records)
- Mining claims must be described "by state, meridian, township, range, section and by aliquot part to the quarter section" (43 CFR 3832.12(a)(1))
- The BLM Control Document Index "is organized by legal land description only" (BLM brochure)
An AOI given as townships and sections lines up with those records without translation.
Defining an AOI by a polygon
A drawn boundary is more precise, but the data it is compared with is not always. BLM's mining claim map data states that "the BLM only requires that mining claims be identified down to the affected quarter section(s)," so a mining claim shown in MLRS covers whole quarter sections even where the staked mining claim covers part of one. A polygon that cuts through a quarter section will catch some mining claims that lie outside it on the ground and miss others. Datums also differ: BLM's mining claim layers use NAD 1983, while USGS MRDS locations are in WGS84.
Practical points
- Extend the AOI to the full quarter sections, or sections, it touches, then trim results against the staked boundaries in the case files
- Include ground around the target, since neighboring mining claims and withdrawals affect access and expansion
- Record the AOI's definition with the date of the search, because the records change
Why it matters in mining claim research
Every result of a mining claim or land status search is only as complete as the AOI behind it. Fitting the boundary to the PLSS units the records use keeps mining claims from being dropped at the edges. See also PLSS, Aliquot Part, Legal Land Description, and Land Status.
Related Terms
GIS
A geographic information system: software and data that store, analyze, and display information tied to locations on the earth.
Claim Density
The number of mining claims in a unit of area, such as a section or township, used to see where ground is being held and how that changes over time.
MRDS
The Mineral Resources Data System, a USGS database of reports on mines, prospects, and mineral occurrences, most complete for the United States, no longer systematically updated.
Claims Research
Finding and reading the records of the mining claims on a tract, from BLM and the county, to learn what is claimed, by whom, and whether the filings were made on time.
Claims Intelligence
Tracking BLM mining claim records over time to see who holds ground in an area, how their positions change, and what those changes suggest.