Spatial Data
Data that identifies where something is on the earth and what it is like, stored as vector features, raster grids, or coordinates in records.
Detailed Definition
Spatial data, or geospatial data, is information tied to a place. BLM's Manual of Surveying Instructions (2009) gives a federal definition: "Geospatial data is information that identifies the geographic location and characteristics of natural or constructed features, including cadastral data about boundaries below, on, and above the surface of the earth. This information may be derived from remote sensing, mapping, and surveying technologies and records" (section 2-38).
The same section defines the National Spatial Data Infrastructure (NSDI) as "the technology, policies, standards, and human resources necessary to acquire, process, store, distribute, and improve utilization of geospatial data." It notes that the Federal Geographic Data Committee (FGDC) "is charged with the responsibility to develop spatial cadastral data content standards for the NSDI."
Forms it takes
- Vector: points, lines, and polygons with attributes. See Vector Data.
- Raster: grids of cells, such as imagery and elevation. See Raster Data.
- Coordinates in records: a latitude and longitude in a table, or a tie to a survey corner in a document.
Every form needs a coordinate system and a datum to mean anything. See Coordinate System and Datum.
Metadata is part of the data
Good spatial data says where it came from and how accurate it is. The FGDC standards, the Manual says, "define the methods for reporting the positional accuracy of geospatial data including cadastral data." BLM's PLSS layers state that the data were "converted from source documents to digital form" in a format "compliant with FGDC Cadastral Data Content Standards and Guidelines for publication." BLM's MLRS mining claim metadata is plain about accuracy: "The positional accuracy across this dataset varies according to the source. The accuracy and precision of the PLSS determines the spatial accuracy and precision of the final location of the geometry in the GIS layer."
What it is not
Both BLM layers carry the same statement: "These data are neither legal documents nor land surveys, and must not be used as such. Official records may be referenced at most BLM offices."
Why it matters in mining claim research
Mining claim research combines spatial data of very different quality: surveyed corners, digitized plats, mining claim cases mapped from legal descriptions, and GPS points. The metadata tells which is which. A layer that does not say how it was made, on what datum, and how accurate it is should be treated as a sketch until it is checked against the record. See Geocoding and GIS.
Related Terms
GIS
A geographic information system: software and data that store, analyze, and display information tied to locations on the earth.
Geospatial Analysis
Using location to answer questions across data layers: what overlaps, what is near, what lies where, and what follows the terrain.
Geocoding
Turning a written location, such as a street address or a legal land description, into map coordinates or a polygon.
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.
Raster Data
GIS data stored as a grid of cells, each holding a value such as an elevation, a color, or a class. Used for imagery and continuous surfaces.
Vector Data
GIS data that stores features as points, lines, and polygons defined by coordinates, each linked to a row of attributes.
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.