Vector Data

Vector data describes features by coordinates. A point is one coordinate pair, a line is an ordered list of them, and a polygon is a closed ring. Esri's shapefile specification puts it this way: "The geometry for a feature is stored as a shape comprising a set of vector coordinates." Each feature is tied to a record of attributes, such as a name, a serial number, or a status.

The three basic shapes

• Points: single locations, such as a corner monument or a sample site
• Lines: ordered vertices, such as a section line, a road, or a stream
• Polygons: closed areas, such as a section, a mining claim, or a withdrawal

Standards spell out the details. GeoJSON (RFC 7946) defines seven geometry types, from "Point" to "GeometryCollection," and requires each polygon ring to be "a closed LineString with four or more positions." Esri's shapefile specification requires closed rings and says "Polygons stored in a shapefile must be clean," with no self-intersections. See GeoJSON and Shapefile.

Topology

Some formats store only shapes. Esri describes the shapefile as storing "nontopological geometry and attribute information." A geodatabase can add topology, which Esri says lets you "create rules to enforce how features behave when they share the same location or boundary." For parcels and survey lines, that keeps shared boundaries from drifting apart. See Feature Class.

Vector versus raster

A vector boundary holds its coordinates at any zoom. A raster boundary is only as fine as its cells, and Esri notes that restructuring data into cells brings "Loss of geometric precision." Surfaces and imagery go the other way and are stored as rasters. See Raster Data.

BLM's vector data

BLM's metadata classes its MLRS mining claim layer as "vector digital data." Its geometries "are primarily derived from Legal Land Descriptions (LLD) for the case and geocoded (mapped) using the Public Land Survey System (PLSS)." The PLSS layers themselves are polygon features for townships, sections, and smaller divisions, which BLM says were "converted from source documents to digital form."

Why it matters in mining claim research

Overlap, acreage, and location questions are answered with vector data. The catch is what the vectors stand for. BLM's metadata states that it "only requires that mining claims be identified down to the affected quarter section(s)," and that quarter sections are what its map will reflect, "most commonly." So a mining claim polygon in the MLRS layer is usually a quarter-section outline, not the staked boundary. A precise polygon can still describe an imprecise location.