switch contour lines based on units

website/src/lib/assets/custom/topo.json

@@ -16,6 +16,12 @@
         "tiles": ["http://localhost:8080/contours_m/{z}/{x}/{y}.mvt"],
         "minzoom": 4,
         "maxzoom": 12
+    },
+    "contours_ft": {
+        "type": "vector",
+        "tiles": ["http://localhost:8080/contours_ft/{z}/{x}/{y}.mvt"],
+        "minzoom": 4,
+        "maxzoom": 12
     }
   },
   "sprite": "https://tiles.openfreemap.org/sprites/ofm_f384/ofm",
@@ -160,6 +166,40 @@
         "line-width": 0.5
       }
     },
+    {
+      "id": "contours_index_ft",
+      "type": "line",
+      "source": "contours_ft",
+      "source-layer": "contours_ft",
+      "filter": [
+        "any",
+        ["all", ["<=", ["zoom"], 11], ["==", ["%", ["get", "ele"], 2000], 0]],
+        ["all", ["==", ["zoom"], 12], ["==", ["%", ["get", "ele"], 800], 0]],
+        ["all", [">=", ["zoom"], 13], ["==", ["%", ["get", "ele"], 400], 0]]
+      ],
+      "paint": {
+        "line-color": "rgb(124, 122, 121)",
+        "line-opacity": 0.1,
+        "line-width": 1.0
+      }
+    },
+    {
+      "id": "contours_ft",
+      "type": "line",
+      "source": "contours_ft",
+      "source-layer": "contours_ft",
+      "filter": [
+        "any",
+        ["all", ["<=", ["zoom"], 11], ["==", ["%", ["get", "ele"], 400], 0]],
+        ["all", ["==", ["zoom"], 12], ["==", ["%", ["get", "ele"], 200], 0]],
+        ["all", [">=", ["zoom"], 13], ["==", ["%", ["get", "ele"], 100], 0]]
+      ],
+      "paint": {
+        "line-color": "rgb(126, 124, 121)",
+        "line-opacity": 0.3,
+        "line-width": 0.5
+      }
+    },
     {
       "id": "landuse_pitch",
       "type": "fill",
@@ -2270,6 +2310,34 @@
         "text-halo-width": 1.25
       }
     },
+    {
+      "id": "contours_label_ft",
+      "type": "symbol",
+      "source": "contours_ft",
+      "source-layer": "contours_ft",
+      "filter": [
+        "any",
+        ["all", ["<=", ["zoom"], 11], ["==", ["%", ["get", "ele"], 2000], 0]],
+        ["all", ["==", ["zoom"], 12], ["==", ["%", ["get", "ele"], 1000], 0]],
+        ["all", ["==", ["zoom"], 13], ["==", ["%", ["get", "ele"], 400], 0]],
+        ["all", [">=", ["zoom"], 14], ["==", ["%", ["get", "ele"], 200], 0]]
+      ],
+      "layout": {
+        "text-size": ["interpolate", ["linear"], ["zoom"], 11, 6, 18, 10],
+        "text-allow-overlap": false,
+        "symbol-avoid-edges": true,
+        "text-ignore-placement": false,
+        "symbol-placement": "line",
+        "text-rotation-alignment": "map",
+        "text-field": "{ele}ft",
+        "text-padding": 0
+      },
+      "paint": {
+        "text-color": "#5c5c5c",
+        "text-halo-color": "rgba(255,255,255,0.85)",
+        "text-halo-width": 1.25
+      }
+    },
     {
       "id": "waterway_line_label",
       "type": "symbol",

website/src/lib/components/map/style.ts

@@ -10,7 +10,8 @@ import {
 import { getLayers } from '$lib/components/map/layer-control/utils';
 import { i18n } from '$lib/i18n.svelte';
 
-const { currentBasemap, currentOverlays, customLayers, opacities, terrainSource } = settings;
+const { currentBasemap, currentOverlays, customLayers, opacities, terrainSource, distanceUnits } =
+    settings;
 
 const emptySource: maplibregl.GeoJSONSourceSpecification = {
     type: 'geojson',
@@ -57,6 +58,9 @@ export class StyleManager {
         opacities.subscribe(() => this.updateOverlays());
         terrainSource.subscribe(() => this.updateTerrain());
         customLayers.subscribe(() => this.updateBasemap());
+        distanceUnits.subscribe(() => {
+            if (get(currentBasemap) === 'topo') this.updateBasemap();
+        });
     }
 
     updateBasemap() {
@@ -217,7 +221,12 @@ export class StyleManager {
 
     merge(style: maplibregl.StyleSpecification, other: maplibregl.StyleSpecification) {
         style.sources = { ...style.sources, ...other.sources };
+        const units = get(distanceUnits);
         for (let layer of other.layers ?? []) {
+            if ('source' in layer) {
+                if (layer.source == 'contours_m' && units === 'imperial') continue;
+                if (layer.source == 'contours_ft' && units !== 'imperial') continue;
+            }
             if (layer.type === 'symbol' && layer.layout && layer.layout['text-field']) {
                 const textField = layer.layout['text-field'];
                 if (