Add US Census Bureau layers

layers/census-bureau/index.js

@@ -0,0 +1,63 @@
+import GeoJSON from 'ol/format/GeoJSON.js';
+import VectorLayer from 'ol/layer/Vector.js';
+import VectorSource from 'ol/source/Vector.js';
+
+import counties20m from './us-counties-20m.geojson?url';
+import counties5m from './us-counties-5m.geojson?url';
+import schoolDistricts from './us-school-districts.geojson?url';
+
+import { Fill, Stroke, Style, Text } from 'ol/style.js';
+
+function style(feature){
+    return new Style({
+        text: new Text({
+            text: feature.get('NAME'),
+        }),
+        fill: new Fill({
+            color: 'rgba(255,255,255,0.4)',
+        }),
+        stroke: new Stroke({
+            color: '#3399CC',
+            width: 1.25,
+        }),
+    });
+}
+
+const layers = {
+    name: "US Census Bureau Data",
+    layers: [
+        {
+            name: "All Counties (2022; low-res)",
+            layer: new VectorLayer({
+                source: new VectorSource({
+                    url: counties20m,
+                    format: new GeoJSON(),
+                }),
+                style: style,
+            }),
+        },
+        {
+            name: "All Counties (2022; medium-res)",
+            layer: new VectorLayer({
+                source: new VectorSource({
+                    url: counties5m,
+                    format: new GeoJSON(),
+                }),
+                style: style,
+            }),
+        },
+        {
+            name: "School Districts (2022; unreasonably large)",
+            layer: new VectorLayer({
+                source: new VectorSource({
+                    url: schoolDistricts,
+                    format: new GeoJSON(),
+                    // TODO: this probably uses projection 'EPSG:4326'
+                }),
+                style: style,
+            }),
+        },
+    ],
+};
+
+export default layers;