fix(web): handle imperial altitude conversion in fixed position

apps/web/src/components/PageComponents/Settings/Position.tsx

@@ -16,6 +16,7 @@ import {
 import { useMyNodeAsProto } from "@core/hooks/useNodesAsProto.ts";
 import { useToast } from "@core/hooks/useToast.ts";
 import { useDevice } from "@core/stores";
+import { feetToMeters, metersToFeet } from "@core/utils/unitConversion.ts";
 import { Protobuf } from "@meshtastic/sdk";
 import { useConfigEditor, useSignal } from "@meshtastic/sdk-react";
 import { LocateFixed } from "lucide-react";
@@ -36,6 +37,10 @@ function UseBrowserLocationButton() {
   const { setValue } = useFormContext<PositionValidation>();
   const { toast } = useToast();
   const { t } = useTranslation("config");
+  const { getEffectiveConfig } = useDevice();
+  const displayUnits = getEffectiveConfig("display")?.units;
+  const isImperial =
+    displayUnits === Protobuf.Config.Config_DisplayConfig_DisplayUnits.IMPERIAL;
   const [busy, setBusy] = useState(false);
 
   if (typeof navigator === "undefined" || !navigator.geolocation) {
@@ -57,7 +62,10 @@ function UseBrowserLocationButton() {
           pos.coords.altitude !== null &&
           !Number.isNaN(pos.coords.altitude)
         ) {
-          setValue("altitude", Math.round(pos.coords.altitude), {
+          const altitudeDisplay = isImperial
+            ? Math.round(metersToFeet(pos.coords.altitude))
+            : Math.round(pos.coords.altitude);
+          setValue("altitude", altitudeDisplay, {
             shouldDirty: true,
           });
         }
@@ -113,8 +121,14 @@ export const Position = ({ onFormInit }: PositionConfigProps) => {
 
   const currentPosition = myNode?.position;
   const displayUnits = getEffectiveConfig("display")?.units;
+  const isImperial =
+    displayUnits === Protobuf.Config.Config_DisplayConfig_DisplayUnits.IMPERIAL;
 
   const formValues = useMemo(() => {
+    const altitudeMeters = currentPosition?.altitude ?? 0;
+    const altitudeDisplay = isImperial
+      ? Math.round(metersToFeet(altitudeMeters))
+      : altitudeMeters;
     return {
       ...config.position,
       ...effectivePosition,
@@ -124,9 +138,9 @@ export const Position = ({ onFormInit }: PositionConfigProps) => {
       longitude: currentPosition?.longitudeI
         ? currentPosition.longitudeI / 1e7
         : undefined,
-      altitude: currentPosition?.altitude ?? 0,
+      altitude: altitudeDisplay,
     } as PositionValidation;
-  }, [config.position, effectivePosition, currentPosition]);
+  }, [config.position, effectivePosition, currentPosition, isImperial]);
 
   const onSubmit = (data: PositionValidation) => {
     const {
@@ -149,13 +163,17 @@ export const Position = ({ onFormInit }: PositionConfigProps) => {
       data.latitude !== undefined &&
       data.longitude !== undefined
     ) {
+      const altitudeMeters =
+        data.altitude != null
+          ? Math.round(isImperial ? feetToMeters(data.altitude) : data.altitude)
+          : 0;
       const message = create(Protobuf.Admin.AdminMessageSchema, {
         payloadVariant: {
           case: "setFixedPosition",
           value: create(Protobuf.Mesh.PositionSchema, {
             latitudeI: Math.round(data.latitude * 1e7),
             longitudeI: Math.round(data.longitude * 1e7),
-            altitude: data.altitude || 0,
+            altitude: altitudeMeters,
             time: Math.floor(Date.now() / 1000),
           }),
         },
@@ -264,7 +282,7 @@ export const Position = ({ onFormInit }: PositionConfigProps) => {
                     : "Meters",
               }),
               properties: {
-                step: 0.0000001,
+                step: 1,
                 suffix:
                   displayUnits ===
                   Protobuf.Config.Config_DisplayConfig_DisplayUnits.IMPERIAL

apps/web/src/core/utils/unitConversion.test.ts

@@ -0,0 +1,38 @@
+import { describe, expect, it } from "vitest";
+
+import { feetToMeters, metersToFeet } from "./unitConversion.ts";
+
+describe("unitConversion", () => {
+  it("converts 1 meter to feet", () => {
+    expect(metersToFeet(1)).toBeCloseTo(3.28084, 5);
+  });
+
+  it("converts 1 foot to meters", () => {
+    expect(feetToMeters(1)).toBeCloseTo(0.3048, 5);
+  });
+
+  it("round-trips 312m ↔ 1024ft (issue #1051 case)", () => {
+    // 312m displayed as feet should be ~1024 ft
+    expect(Math.round(metersToFeet(312))).toBe(1024);
+    // 1025 ft stored as meters should be ~312m
+    expect(Math.round(feetToMeters(1025))).toBe(312);
+  });
+
+  it("round-trips within 1 ft for integer meters (firmware int32 loss)", () => {
+    for (const m of [0, 100, 312, 1000]) {
+      const ft = Math.round(metersToFeet(m));
+      const m2 = Math.round(feetToMeters(ft));
+      expect(Math.abs(m - m2)).toBeLessThanOrEqual(1);
+    }
+  });
+
+  it("handles zero", () => {
+    expect(metersToFeet(0)).toBe(0);
+    expect(feetToMeters(0)).toBe(0);
+  });
+
+  it("handles negative (below sea level, e.g., Dead Sea)", () => {
+    expect(metersToFeet(-430)).toBeCloseTo(-1410.76, 1);
+    expect(feetToMeters(-1410)).toBeCloseTo(-430, 0);
+  });
+});

apps/web/src/core/utils/unitConversion.ts

@@ -0,0 +1,16 @@
+/**
+ * Altitude unit conversion — pure functions, canonical is meters
+ * (firmware Position.altitude int32 meters per mesh_pb.ts).
+ * Display in feet when DisplayUnits is IMPERIAL.
+ */
+
+export const FEET_PER_METER = 3.28084;
+export const METERS_PER_FOOT = 0.3048;
+
+export function metersToFeet(meters: number): number {
+  return meters * FEET_PER_METER;
+}
+
+export function feetToMeters(feet: number): number {
+  return feet * METERS_PER_FOOT;
+}