GIS
A geographic information system: software and data that store, analyze, and display information tied to locations on the earth.
Detailed Definition
A geographic information system (GIS) is software plus data that ties information to places. The U.S. Geological Survey (USGS) defines it this way: "A Geographic Information System (GIS) is a computer system that analyzes and displays geographically referenced information. It uses data that is attached to a unique location."
The core idea is layers of data, lined up by location, with questions asked across them. See Geospatial Analysis.
What goes into a GIS
- Vector data: points, lines, and polygons with attribute tables. Section lines and mining claim polygons are vector data. See Vector Data.
- Raster data: grids of cells, such as elevation models and aerial images. See Raster Data and DEM.
- A coordinate reference: every layer has a datum and a coordinate system, and layers line up only when those are handled correctly. See Datum and Coordinate System.
- Storage and delivery: files such as shapefiles and geodatabases, and web services that stream maps or features. See Geodatabase and Web Map Service.
Where the land data comes from
BLM publishes the Public Land Survey System (PLSS) as GIS data. Its national PLSS layer "represents the GIS Version of the Public Land Survey System including both rectangular and non-rectangular surveys." The primary source is "cadastral survey records housed by the BLM," and the data "has been converted from source documents to digital form." BLM's Manual of Surveying Instructions (2009) states the relationship plainly: "the spatial depiction of the PLSS in a digital land information system is a byproduct of the abstraction of data from official survey records" (section 2-37).
BLM also publishes mining claim cases from its Mineral and Land Records System (MLRS) as a GIS layer. Its metadata says "The BLM only requires that mining claims be identified down to the affected quarter section(s)," and that boundaries as staked and monumented are found in the accepted notice or certificate of location in the official case file.
Limits BLM states
Both layers carry the same warning: "These data are neither legal documents nor land surveys, and must not be used as such." And: "The data are not better than the original sources from which they were derived, and both scale and accuracy may vary across the data set."
Why it matters in mining claim research
A GIS puts mining claim records, the PLSS grid, land status, and terrain on one map, which is how overlaps and gaps get found. But a polygon on screen is a drawing of a record, often at quarter-section precision. Where the exact ground matters, the answer is in the location notice, the plat, and the field notes.
Related Terms
PLSS
The Public Land Survey System, the rectangular survey system that divides the public lands into townships, ranges, and sections and serves as the basis for describing them.
Geospatial AI
Artificial intelligence applied to maps, imagery, and location data. USGS uses machine learning to georeference historical maps and model mineral prospectivity.
Remote Sensing
Gathering information about the Earth from a distance by measuring reflected and emitted energy, usually from satellites or aircraft.
Geodatabase
Esri's native format for GIS data: feature classes, tables, rasters, and the rules between them, held in a folder, a single file, or a relational database.
Shapefile
Esri's published vector data format: a main file of shapes (.shp), an index (.shx), and a dBASE attribute table (.dbf) that travel together.
GeoJSON
An IETF standard (RFC 7946) for encoding geographic features in JSON, with coordinates in WGS 84 longitude and latitude, in that order.
Feature Class
In Esri's geodatabase model, a collection of features that share one geometry type (point, line, or polygon) and one set of attribute fields.
Web Map Service
An Open Geospatial Consortium (OGC) standard for requesting georeferenced map images from a server over HTTP. It returns pictures of data, not the data itself.
Spatial Join
A GIS operation that copies attributes from one layer to another based on where features sit relative to each other, not on a shared field.
Buffer Analysis
A GIS operation that draws polygons a set distance around points, lines, or polygons, used to find what lies within that distance.
Coordinate System
The rules that turn a position into numbers: latitude and longitude on a datum, or eastings and northings on a projected grid such as UTM or State Plane.