Web Feature Service
An Open Geospatial Consortium (OGC) standard for querying and retrieving geographic features, with geometry and attributes, from a server over the web.
Detailed Definition
A Web Feature Service (WFS) delivers features themselves: geometry plus attributes. Where a Web Map Service returns a picture, WFS returns data. The Open Geospatial Consortium (OGC) puts it this way: "Rather than sharing geographic information at the file level using File Transfer Protocol (FTP), for example, the WFS offers direct fine-grained access to geographic information at the feature and feature property level."
OGC's standards page lists the Web Feature Service 2.0 Interface Standard, version 2.0.2 (OGC 09-025r2). Version 2.0 is also ISO 19142.
What it can do
OGC says the standard "covers 11 operations," in five groups:
- Discovery, to "determine its capabilities and to retrieve the application schema that defines the feature types that the service offers." GetCapabilities is the discovery operation OGC names.
- Query, where features are "retrieved from the underlying data store based upon constraints, defined by the client, on feature properties."
- Locking, for "exclusive access to features for the purpose of modifying or deleting features."
- Transaction, where features are "created, changed, replaced and deleted from the underlying data store."
- Stored queries, parameterized queries kept on the server that "can be repeatedly invoked using different parameter values."
The successor
OGC now steers new work elsewhere: "the functional capabilities are now available in a more modern web API, OGC API – Features, and implementers are encouraged to use the newer Standard." Part 1, "Core," is "restricted to fetching features where geometries are represented in the coordinate reference system WGS 84 with axis order longitude/latitude." Part 2 covers other coordinate systems. Part 1 was also published as ISO 19168-1:2020, and its discovery and query operations use HTTP GET.
BLM's services
BLM's national PLSS and MLRS land status layers are published as ArcGIS REST map services with their own query operation. Their service pages list supported query formats of "JSON, geoJSON, PBF" and a MaxRecordCount of 2000. See GeoJSON.
Why it matters in mining claim research
Feature services let mining claim and PLSS data be pulled straight from the source into analysis. Three settings decide whether the pull is complete and correct: the query filter, the record limit the service advertises, and the coordinate system of the output. A download that stops at the server's record limit, or that arrives on WGS 84 when the analysis assumes NAD 83, gives a wrong answer that looks right. See Coordinate System.
Related Terms
GIS
A geographic information system: software and data that store, analyze, and display information tied to locations on the earth.
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.
API
Application Programming Interface: a defined access point that lets one program request data or functions from another. Many government data services publish APIs.
GeoJSON
An IETF standard (RFC 7946) for encoding geographic features in JSON, with coordinates in WGS 84 longitude and latitude, in that order.
Vector Data
GIS data that stores features as points, lines, and polygons defined by coordinates, each linked to a row of attributes.
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.
Tile Service
A map service that delivers pre-rendered map tiles at fixed scales, so a viewer loads only the tiles it needs. OGC standardizes it as WMTS and OGC API - Tiles.