Methodology and data sources

Data refreshed September 17, 2026. A GitHub Actions job runs the pipeline nightly, rebuilds every page and redeploys the site.

Boundaries

Each type comes from one public ArcGIS REST service. The polygons are requested in WGS84 and generalized by the server to a tolerance of a few hundred meters so the download stays small. That generalized geometry is what the maps show and what the derived figures are measured from.

National wildlife refuges (549): the Fish and Wildlife Service National Wildlife Refuge System Boundaries layer, filtered to records typed NWR. Records that share a refuge name are merged into one unit. The layer also carries waterfowl production areas, fish hatcheries and coordination areas, which are left out.
Wilderness areas (806): the Wilderness Areas in the United States layer published by Wilderness Connect, a partnership of the University of Montana and the four wilderness agencies. A wilderness managed by two agencies has two records in the layer; they are merged by the wilderness id, the acreage summed and both agencies listed.
National forests and grasslands (112): the Forest Service Administrative Forest Boundaries layer from the Enterprise Data Warehouse. The URL of each forest page uses the Forest Service organization code, so other sites can link to a forest by code.
BLM national monuments and conservation areas (56): the Bureau of Land Management National Monuments, National Conservation Areas and Similar Designations layer. One record describing a designated road area inside a monument is left out. Where the layer omits the designation from a name, the designation is taken from the layer’s category code; a few names in the layer carry no code and are shown as the layer spells them.

Derived facts

Acreage. Wilderness areas use the Wilderness Connect acreage field and forests use the Forest Service gis_acres field. Refuges and BLM units carry no acreage in their layers, so the site computes the geodesic area of the polygon on the WGS84 ellipsoid. Because the polygon is generalized and may include water, easements or inholdings, that figure can differ from the agency’s official acreage, and the pages say so.
States. Wilderness areas use the state field in the Wilderness Connect layer. For the other types the boundary is intersected with Census state polygons and a state is listed when it holds at least one percent of the area. A boundary that touches no state polygon, such as an offshore refuge, is assigned the nearest state.
Center point. The centroid of the boundary, or a point inside the boundary when the centroid falls outside it. Live widgets, the night-sky reading and the distance to Forest Service sites all use this point.
Where to camp. Federal campgrounds from the Campsite Atlas index (Recreation.gov and Forest Service records) whose point falls inside the boundary or within ten miles of its edge. Distances are from the campground point to the nearest point on the boundary.
Trailheads and sites. The Forest Service Recreation Opportunities layer. Forest pages take every point carrying the forest’s organization code; wilderness pages take the points that fall inside the boundary. Marker categories that are not places (group headers and shields) are left out. Up to 60 sites nearest the center point are listed and the total is stated.
Nearby on the other atlases. National Park System units within 30 miles of the boundary, from Park Atlas, and National Register listings within 15 miles, from Register Atlas, landmarks first.
Night sky. NASA’s Black Marble night-lights image (VIIRS, 2016 composite) sampled at zoom 6 as a 5 by 5 pixel mean around the center point, on a 0 to 255 scale. The word on the page follows fixed bands: under 20 is about as dark as the ground gets, under 40 very dark, under 80 some glow, under 150 noticeable light pollution, and above that bright skies nearby.

Descriptions

Wilderness pages quote the short description in the Wilderness Connect record and link to the full text on wilderness.net. Refuge, forest and BLM pages quote the opening of the Wikipedia article about the unit, under the Creative Commons Attribution-ShareAlike 4.0 license, with a link to the article. The article is found by searching Wikipedia for the unit’s name and is accepted only when the title of the top result contains that name, so a refuge never gets the article about the town it is named after. Matches so far: 489 of 549 refuges, 94 of 112 forests and 41 of 56 BLM units. Pages without a match say so rather than showing a wrong article.

Official links

Wilderness pages link to the Wilderness Connect page in the record. Refuge pages link to fws.gov/refuge/ followed by the refuge name in lower case without the words National Wildlife Refuge; each link is requested during the build and kept only when the server answers 200, otherwise the page links to a search on fws.gov. 528 of 549 refuge links verified on the last run. Forest pages link to the fs.usda.gov address found in that forest’s recreation records, verified the same way; 107 of 112 verified. The BLM layer carries no page addresses, so BLM pages link to a search on blm.gov.

Live conditions

Weather and alerts come from the National Weather Service, air quality from EPA AirNow through a small proxy that holds the key, river flow from USGS gauges, earthquakes from the USGS feed, wildlife observations from iNaturalist, and wildfire incidents from the interagency WFIGS feed fetched nightly. These load in the browser when a page is opened and are not stored.

Known limitations

Boundaries are simplified for display. Small parcels and inholdings may not appear, and the agency map is authoritative.
Computed acreage for refuges and BLM units is a measure of the polygon, not the agency’s legal acreage.
Wikipedia text reflects the article at the time of the nightly run and may lag changes to the unit.
Campground and recreation site lists depend on the sibling indexes and the Forest Service layer being current.

The open-data files are documented on the data page. Corrections can be raised at github.com/kirkwood-justin/site4/issues.