Add MN Ambulance Service Areas layer

Requested-By: Isaac Swift

layers/index.js

@@ -21,6 +21,7 @@ import survey_markers from './survey-markers/index.js';
 import tjx from './tjx/index.js';
 import minnesotaAdventureTrails from './minnesota-adventure-trails/index.js';
 import cropHistory from './crop-history/index.js';
+import mnAmbulanceServiceAreas from './mn-ambulance-service-areas/layer.js';
 
 const layerCategories = [
     { // Base maps
@@ -90,6 +91,7 @@ const layerCategories = [
                 name: "Bikepacking.com Routes",
                 layer: bikepackingLayer,
             },
+            mnAmbulanceServiceAreas,
         ]
     },
     minnesotaAdventureTrails,

layers/mn-ambulance-service-areas/README.md

@@ -0,0 +1,3 @@
+https://mn.gov/oems/ambulance-services/primary-service-area-maps.jsp
+
+https://experience.arcgis.com/experience/a222fe7ceaf44f868ec3c0f5dafe8446/page/Page

layers/mn-ambulance-service-areas/get_data.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env nix-shell
+#! nix-shell -i python3 -p python3 python3Packages.requests python3Packages.shapely
+
+import requests
+import json
+from collections import defaultdict
+from shapely.geometry import shape, mapping
+from shapely.ops import unary_union
+
+# https://services.arcgis.com/9OIuDHbyhmH91RfZ/arcgis/rest/services/EMSRB_Statewide/FeatureServer/0/query?f=pbf&cacheHint=true&maxRecordCountFactor=4&resultOffset=0&resultRecordCount=8000&where=1%3D1&orderByFields=OBJECTID%20ASC&outFields=AmbServNam%2CCounty%2COBJECTID&outSR=102100&spatialRel=esriSpatialRelIntersects
+
+url = "https://services.arcgis.com/9OIuDHbyhmH91RfZ/arcgis/rest/services/EMSRB_Statewide/FeatureServer/0/query"
+params = {
+    "f": "geojson",
+    "cacheHint": "true",
+    "maxRecordCountFactor": "4",
+    "resultOffset": "0",
+    "resultRecordCount": "8000",
+    "where": "1=1",
+    "outFields": "AmbServNam,County",
+    "outSR": "102100",
+    "spatialRel": "esriSpatialRelIntersects",
+}
+
+response = requests.get(url, params=params)
+response.raise_for_status()
+
+data = json.loads(response.text)
+
+services = defaultdict(list)
+
+for feature in data["features"]:
+    service_name = feature["properties"].get("AmbServNam", "Unknown")
+    services[service_name].append(feature)
+
+merged_features = []
+
+for service_name, features in services.items():
+    merged_features.append(
+        {
+            "type": "Feature",
+            "properties": {
+                "AmbServNam": service_name,
+            },
+            "geometry": mapping(unary_union([shape(feature["geometry"]) for feature in features])),
+        }
+    )
+
+merged_data = {
+    "type": "FeatureCollection",
+    "crs": {"type": "name", "properties": {"name": "EPSG:3857"}},
+    "features": merged_features,
+}
+
+with open("mn-ambulance-service-areas.geojson", "w", encoding="utf-8") as f:
+    json.dump(merged_data, f)

layers/mn-ambulance-service-areas/layer.js

@@ -0,0 +1,54 @@
+import GeoJSON from 'ol/format/GeoJSON.js';
+import VectorLayer from 'ol/layer/Vector.js';
+import VectorSource from 'ol/source/Vector.js';
+
+import serviceAreas from './mn-ambulance-service-areas.geojson?url';
+
+import { Fill, Stroke, Style, Text } from 'ol/style.js';
+
+window.chosenColors = {};
+window.chosenColors2 = {};
+
+function style(feature){
+    const name = feature.get('AmbServNam');
+    // // djb2 -- results in very non-uniform distribution
+    // // https://web.archive.org/web/20251011200517/https://www.cse.yorku.ca/~oz/hash.html
+    // let hash = 5381;
+    // for (let i = 0; i < name.length; i++) {
+    //     hash = hash * 33 + name.charCodeAt(i);
+    // }
+    // const colorDeg = hash % 360;
+
+    // erichash -- thanks @villnoweric
+    let hash = 0;
+    for (let i = 0; i < name.length; i++) {
+        hash += name.charCodeAt(i);
+    }
+    let colorDeg = hash % 360;
+
+    return new Style({
+        text: new Text({
+            text: name,
+        }),
+        fill: new Fill({
+            color: `lch(50% 50 ${colorDeg} / 40%)`,
+        }),
+        stroke: new Stroke({
+            color: `lch(50% 50 ${colorDeg})`,
+            width: 1.25,
+        }),
+    });
+}
+
+const layer = {
+    name: "MN Ambulance Service Areas",
+    layer: new VectorLayer({
+        source: new VectorSource({
+            url: serviceAreas,
+            format: new GeoJSON(),
+        }),
+        style: style,
+    }),
+};
+
+export default layer;