feat: Add UWB integration — follow mode, range presets, UWB status

UWBModels.swift (new):
- FollowMode enum: .gps / .uwb — publishes {"mode":"gps|uwb"} to saltybot/follow/mode
- FollowPreset enum: .close(1.5m) / .medium(3m) / .far(5m) — publishes
  {"range_m":N,"preset":"..."} to saltybot/follow/range
- UWBPosition struct: x/y/z + timestamp
- UWBRange struct: anchorID + rangeMetres + timestamp

SensorManager:
- Subscribes to saltybot/uwb/range + saltybot/uwb/position on startStreaming
- handleUWBRange: updates uwbRanges[anchorID] (keyed dict)
- handleUWBPosition: updates uwbPosition + sets uwbActive=true
- UWB staleness watchdog (1Hz timer): clears uwbActive and prunes stale ranges >3s
- setFollowMode(_:) / setFollowPreset(_:): update state + publish to MQTT immediately
- Publishes current follow mode+range on connect

MapContentView:
- UWB status badge (top-left): green/gray dot, "UWB Active|Out of Range",
  per-anchor range readouts (e.g. A1 2.34m)
- Follow mode segmented control: GPS | UWB
- Follow range segmented control: Close | Medium | Far (shows metres)
- MapCircle follow-range ring around robot: green inside, orange outside range
- Stats bar: distance turns green + checkmark when user is inside follow range;
  UWB (x,y) coord shown when UWB mode active and position known

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SulTee/SulTee.xcodeproj/project.pbxproj

@@ -14,6 +14,7 @@
 		A100000100000000000005AA /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = A100000100000000000005AB /* Assets.xcassets */; };
 		A100000100000000000009AA /* MQTTClient.swift in Sources */ = {isa = PBXBuildFile; fileRef = A100000100000000000009AB /* MQTTClient.swift */; };
 		A10000010000000000000AAA /* MapContentView.swift in Sources */ = {isa = PBXBuildFile; fileRef = A10000010000000000000AAB /* MapContentView.swift */; };
+		A10000010000000000000BAA /* UWBModels.swift in Sources */ = {isa = PBXBuildFile; fileRef = A10000010000000000000BAB /* UWBModels.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
@@ -26,6 +27,7 @@
 		A100000100000000000007AB /* SulTee.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = SulTee.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		A100000100000000000009AB /* MQTTClient.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MQTTClient.swift; sourceTree = "<group>"; };
 		A10000010000000000000AAB /* MapContentView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MapContentView.swift; sourceTree = "<group>"; };
+		A10000010000000000000BAB /* UWBModels.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UWBModels.swift; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -56,6 +58,7 @@
 				A100000100000000000004AB /* WebSocketClient.swift */,
 				A100000100000000000009AB /* MQTTClient.swift */,
 				A10000010000000000000AAB /* MapContentView.swift */,
+				A10000010000000000000BAB /* UWBModels.swift */,
 				A100000100000000000005AB /* Assets.xcassets */,
 				A100000100000000000006AB /* Info.plist */,
 			);
@@ -146,6 +149,7 @@
 				A100000100000000000004AA /* WebSocketClient.swift in Sources */,
 				A100000100000000000009AA /* MQTTClient.swift in Sources */,
 				A10000010000000000000AAA /* MapContentView.swift in Sources */,
+				A10000010000000000000BAA /* UWBModels.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

SulTee/SulTee/MapContentView.swift

@@ -1,18 +1,33 @@
 import SwiftUI
 import MapKit
 
+extension CLLocationCoordinate2D: @retroactive Equatable {
+    public static func == (lhs: CLLocationCoordinate2D, rhs: CLLocationCoordinate2D) -> Bool {
+        lhs.latitude == rhs.latitude && lhs.longitude == rhs.longitude
+    }
+}
+
 /// Full-screen map showing user (blue) and robot (orange) positions,
-/// a follow-path line between them, and fading breadcrumb trails for both.
+/// a follow-path line, fading breadcrumb trails, UWB status, and follow controls.
 struct MapContentView: View {
     @EnvironmentObject var sensor: SensorManager
 
     @State private var position:    MapCameraPosition = .automatic
     @State private var followUser   = true
 
+    private var insideFollowRange: Bool {
+        guard let d = sensor.distanceToRobot else { return false }
+        return d <= sensor.followPreset.metres
+    }
+
     var body: some View {
         ZStack(alignment: .bottom) {
             map
-            overlay
+            VStack(spacing: 0) {
+                Spacer()
+                followControls
+                statsBar
+            }
         }
         .ignoresSafeArea(edges: .top)
         .onChange(of: sensor.userLocation) { _, coord in
@@ -20,20 +35,32 @@ struct MapContentView: View {
                 withAnimation(.easeInOut(duration: 0.4)) {
                     position = .camera(MapCamera(
                         centerCoordinate: coord,
-                        distance: 400,
+                        distance: 400, heading: 0, pitch: 0
-                        heading: 0,
-                        pitch: 0
                     ))
                 }
             }
         }
     }
 
-    // MARK: - Map
+    // MARK: - Map content
 
     private var map: some View {
         Map(position: $position) {
 
+            // ── Follow range circle around robot
+            if let robotLoc = sensor.robotLocation {
+                MapCircle(center: robotLoc, radius: sensor.followPreset.metres)
+                    .foregroundStyle(
+                        insideFollowRange
+                            ? Color.green.opacity(0.12)
+                            : Color.orange.opacity(0.12)
+                    )
+                    .stroke(
+                        insideFollowRange ? Color.green : Color.orange,
+                        style: StrokeStyle(lineWidth: 1.5)
+                    )
+            }
+
             // ── User breadcrumb trail (fading blue dots)
             let userCrumbs = sensor.userBreadcrumbs
             ForEach(userCrumbs.indices, id: \.self) { idx in
@@ -69,15 +96,9 @@ struct MapContentView: View {
             if let userLoc = sensor.userLocation {
                 Annotation("You", coordinate: userLoc) {
                     ZStack {
-                        Circle()
+                        Circle().fill(.blue.opacity(0.25)).frame(width: 36, height: 36)
-                            .fill(.blue.opacity(0.25))
+                        Circle().fill(.blue).frame(width: 16, height: 16)
-                            .frame(width: 36, height: 36)
+                        Circle().stroke(.white, lineWidth: 2.5).frame(width: 16, height: 16)
-                        Circle()
-                            .fill(.blue)
-                            .frame(width: 16, height: 16)
-                        Circle()
-                            .stroke(.white, lineWidth: 2.5)
-                            .frame(width: 16, height: 16)
                     }
                 }
             }
@@ -86,9 +107,7 @@ struct MapContentView: View {
             if let robotLoc = sensor.robotLocation {
                 Annotation("Robot", coordinate: robotLoc) {
                     ZStack {
-                        Circle()
+                        Circle().fill(.orange.opacity(0.25)).frame(width: 36, height: 36)
-                            .fill(.orange.opacity(0.25))
-                            .frame(width: 36, height: 36)
                         Image(systemName: "car.fill")
                             .font(.system(size: 16, weight: .bold))
                             .foregroundStyle(.white)
@@ -99,27 +118,54 @@ struct MapContentView: View {
             }
         }
         .mapStyle(.standard(elevation: .realistic))
-        .onMapCameraChange { _ in
+        .onMapCameraChange { _ in followUser = false }
-            // User dragged map → stop auto-follow
+        .overlay(alignment: .topTrailing) { recenterButton }
-            followUser = false
+        .overlay(alignment: .topLeading)  { uwbBadge }
-        }
-        .overlay(alignment: .topTrailing) {
-            followButton
-        }
     }
 
-    // MARK: - Re-centre button
+    // MARK: - UWB status badge (top-left)
 
-    private var followButton: some View {
+    private var uwbBadge: some View {
+        VStack(alignment: .leading, spacing: 4) {
+            HStack(spacing: 6) {
+                Circle()
+                    .fill(sensor.uwbActive ? Color.green : Color.gray)
+                    .frame(width: 9, height: 9)
+                    .shadow(color: sensor.uwbActive ? .green : .clear, radius: 4)
+                Text(sensor.uwbActive ? "UWB Active" : "UWB Out of Range")
+                    .font(.caption2.bold())
+                    .foregroundStyle(sensor.uwbActive ? .primary : .secondary)
+            }
+
+            // Per-anchor ranges
+            let sortedRanges = sensor.uwbRanges.values.sorted { $0.anchorID < $1.anchorID }
+            if !sortedRanges.isEmpty {
+                HStack(spacing: 8) {
+                    ForEach(sortedRanges) { r in
+                        Text("\(r.anchorID) \(r.rangeMetres, specifier: "%.2f")m")
+                            .font(.caption2)
+                            .foregroundStyle(.secondary)
+                    }
+                }
+            }
+        }
+        .padding(.horizontal, 10)
+        .padding(.vertical, 7)
+        .background(.ultraThinMaterial, in: RoundedRectangle(cornerRadius: 10))
+        .padding(.top, 56)   // below status bar
+        .padding(.leading, 16)
+    }
+
+    // MARK: - Re-centre button (top-right)
+
+    private var recenterButton: some View {
         Button {
             followUser = true
             if let coord = sensor.userLocation {
                 withAnimation {
                     position = .camera(MapCamera(
                         centerCoordinate: coord,
-                        distance: 400,
+                        distance: 400, heading: 0, pitch: 0
-                        heading: 0,
-                        pitch: 0
                     ))
                 }
             }
@@ -128,24 +174,84 @@ struct MapContentView: View {
                 .padding(10)
                 .background(.ultraThinMaterial, in: Circle())
         }
-        .padding([.top, .trailing], 16)
+        .padding(.top, 56)
-        .padding(.top, 44)  // below nav bar
+        .padding(.trailing, 16)
     }
 
-    // MARK: - Stats overlay
+    // MARK: - Follow controls panel
 
-    private var overlay: some View {
+    private var followControls: some View {
+        VStack(spacing: 10) {
+
+            // Follow mode: GPS | UWB
+            VStack(alignment: .leading, spacing: 4) {
+                Label("Follow Mode", systemImage: "location.circle")
+                    .font(.caption.bold())
+                    .foregroundStyle(.secondary)
+                Picker("Follow Mode", selection: Binding(
+                    get:  { sensor.followMode },
+                    set:  { sensor.setFollowMode($0) }
+                )) {
+                    ForEach(FollowMode.allCases) { mode in
+                        Text(mode.rawValue).tag(mode)
+                    }
+                }
+                .pickerStyle(.segmented)
+            }
+
+            // Follow range: Close | Medium | Far
+            VStack(alignment: .leading, spacing: 4) {
+                HStack {
+                    Label("Follow Range", systemImage: "circle.dashed")
+                        .font(.caption.bold())
+                        .foregroundStyle(.secondary)
+                    Spacer()
+                    Text("\(sensor.followPreset.metres, specifier: "%.1f") m")
+                        .font(.caption.monospacedDigit())
+                        .foregroundStyle(.secondary)
+                }
+                Picker("Range", selection: Binding(
+                    get:  { sensor.followPreset },
+                    set:  { sensor.setFollowPreset($0) }
+                )) {
+                    ForEach(FollowPreset.allCases) { preset in
+                        Text(preset.rawValue).tag(preset)
+                    }
+                }
+                .pickerStyle(.segmented)
+            }
+        }
+        .padding(.horizontal, 16)
+        .padding(.vertical, 12)
+        .background(.ultraThinMaterial, in: RoundedRectangle(cornerRadius: 16))
+        .padding(.horizontal, 16)
+        .padding(.bottom, 8)
+    }
+
+    // MARK: - Stats bar
+
+    private var statsBar: some View {
         HStack(spacing: 20) {
             if let dist = sensor.distanceToRobot {
-                statCell(value: distanceString(dist),
+                statCell(
+                    value: distanceString(dist),
                     label: "distance",
-                         icon:  "arrow.left.and.right")
+                    icon:  insideFollowRange ? "checkmark.circle.fill" : "arrow.left.and.right",
+                    tint:  insideFollowRange ? .green : .primary
+                )
             }
             if sensor.robotSpeed > 0.2 {
                 statCell(value: String(format: "%.1f m/s", sensor.robotSpeed),
                          label: "robot spd",
                          icon:  "speedometer")
             }
+            if sensor.followMode == .uwb, let pos = sensor.uwbPosition {
+                statCell(
+                    value: String(format: "(%.1f, %.1f)", pos.x, pos.y),
+                    label: "UWB pos",
+                    icon:  "waveform"
+                )
+            }
             if !sensor.isStreaming {
                 Text("Start Follow-Me to stream")
                     .font(.caption)
@@ -159,22 +265,25 @@ struct MapContentView: View {
         .padding(.horizontal, 16)
     }
 
-    private func statCell(value: String, label: String, icon: String) -> some View {
+    // MARK: - Helpers
+
+    private func statCell(value: String,
+                          label: String,
+                          icon: String,
+                          tint: Color = .primary) -> some View {
         HStack(spacing: 6) {
             Image(systemName: icon)
-                .foregroundStyle(.secondary)
+                .foregroundStyle(tint == .primary ? .secondary : tint)
                 .font(.caption)
             VStack(alignment: .leading, spacing: 0) {
-                Text(value).font(.headline.monospacedDigit())
+                Text(value).font(.headline.monospacedDigit()).foregroundStyle(tint)
                 Text(label).font(.caption2).foregroundStyle(.secondary)
             }
         }
     }
 
-    private func distanceString(_ metres: Double) -> String {
+    private func distanceString(_ m: Double) -> String {
-        metres < 1000
+        m < 1000 ? "\(Int(m)) m" : String(format: "%.1f km", m / 1000)
-            ? "\(Int(metres)) m"
-            : String(format: "%.1f km", metres / 1000)
     }
 }
 

SulTee/SulTee/SensorManager.swift

@@ -4,8 +4,8 @@ import CoreMotion
 import MapKit
 import Combine
 
-/// Manages all iPhone sensors, publishes iOS GPS to MQTT, subscribes to robot GPS,
+/// Manages all iPhone sensors, publishes iOS GPS to MQTT, subscribes to robot GPS
-/// and exposes state for the map and status views.
+/// and UWB data, and exposes state for the map and status views.
 final class SensorManager: NSObject, ObservableObject {
 
     // MARK: - Streaming state
@@ -25,17 +25,25 @@ final class SensorManager: NSObject, ObservableObject {
     @Published var userLocation:    CLLocationCoordinate2D? = nil
     @Published var userBreadcrumbs: [CLLocationCoordinate2D] = []
 
-    // MARK: - Robot position (from MQTT saltybot/phone/gps)
+    // MARK: - Robot position (saltybot/phone/gps)
 
     @Published var robotLocation:    CLLocationCoordinate2D? = nil
     @Published var robotBreadcrumbs: [CLLocationCoordinate2D] = []
     @Published var robotSpeed:       Double = 0
-
-    // MARK: - Derived
-
     @Published var distanceToRobot:  Double? = nil
 
-    // MARK: - WebSocket config (sensor stream to Orin)
+    // MARK: - UWB (saltybot/uwb/range + saltybot/uwb/position)
+
+    @Published var uwbPosition: UWBPosition? = nil
+    @Published var uwbRanges:   [String: UWBRange] = [:]   // anchorID → UWBRange
+    @Published var uwbActive:   Bool = false
+
+    // MARK: - Follow settings
+
+    @Published var followMode:   FollowMode   = .gps
+    @Published var followPreset: FollowPreset = .medium
+
+    // MARK: - WebSocket config
 
     static let defaultOrinURL  = "ws://100.64.0.2:9090"
     private static let orinURLKey = "orinURL"
@@ -56,12 +64,19 @@ final class SensorManager: NSObject, ObservableObject {
         password: "mqtt_pass",
         clientID: "saul-t-mote-\(UUID().uuidString.prefix(8))"
     ))
+
     private static let iosGPSTopic      = "saltybot/ios/gps"
     private static let robotGPSTopic    = "saltybot/phone/gps"
+    private static let uwbRangeTopic    = "saltybot/uwb/range"
+    private static let uwbPositionTopic = "saltybot/uwb/position"
+    private static let followModeTopic  = "saltybot/follow/mode"
+    private static let followRangeTopic = "saltybot/follow/range"
     private static let maxBreadcrumbs   = 60
+    private static let uwbStaleSeconds  = 3.0
 
     private var lastKnownLocation:  CLLocation?
     private var mqttPublishTimer:   Timer?
+    private var uwbStalenessTimer:  Timer?
 
     // MARK: - Sensors
 
@@ -81,8 +96,8 @@ final class SensorManager: NSObject, ObservableObject {
     // MARK: - Init
 
     override init() {
-        let urlString = UserDefaults.standard.string(forKey: Self.orinURLKey) ?? Self.defaultOrinURL
+        let urlStr = UserDefaults.standard.string(forKey: Self.orinURLKey) ?? Self.defaultOrinURL
-        self.ws = WebSocketClient(url: URL(string: urlString) ?? URL(string: Self.defaultOrinURL)!)
+        self.ws = WebSocketClient(url: URL(string: urlStr) ?? URL(string: Self.defaultOrinURL)!)
         super.init()
 
         locationManager.delegate = self
@@ -98,8 +113,13 @@ final class SensorManager: NSObject, ObservableObject {
             .store(in: &cancellables)
 
         mqtt.onMessage = { [weak self] topic, payload in
-            guard let self, topic == Self.robotGPSTopic else { return }
+            guard let self else { return }
-            self.handleRobotGPS(payload)
+            switch topic {
+            case Self.robotGPSTopic:    self.handleRobotGPS(payload)
+            case Self.uwbRangeTopic:    self.handleUWBRange(payload)
+            case Self.uwbPositionTopic: self.handleUWBPosition(payload)
+            default: break
+            }
         }
     }
 
@@ -111,9 +131,15 @@ final class SensorManager: NSObject, ObservableObject {
         ws.connect()
         mqtt.connect()
         mqtt.subscribe(topic: Self.robotGPSTopic)
+        mqtt.subscribe(topic: Self.uwbRangeTopic)
+        mqtt.subscribe(topic: Self.uwbPositionTopic)
         requestPermissionsAndStartSensors()
         startRateTimer()
         startMQTTPublishTimer()
+        startUWBStalenessTimer()
+        // Publish current follow settings immediately on connect
+        publishFollowMode()
+        publishFollowPreset()
     }
 
     func stopStreaming() {
@@ -124,6 +150,7 @@ final class SensorManager: NSObject, ObservableObject {
         stopSensors()
         rateTimer?.invalidate();         rateTimer = nil
         mqttPublishTimer?.invalidate();  mqttPublishTimer = nil
+        uwbStalenessTimer?.invalidate(); uwbStalenessTimer = nil
     }
 
     func updateURL(_ urlString: String) {
@@ -134,6 +161,28 @@ final class SensorManager: NSObject, ObservableObject {
         }
     }
 
+    /// Change follow mode and publish to MQTT immediately.
+    func setFollowMode(_ mode: FollowMode) {
+        followMode = mode
+        publishFollowMode()
+    }
+
+    /// Change follow range preset and publish to MQTT immediately.
+    func setFollowPreset(_ preset: FollowPreset) {
+        followPreset = preset
+        publishFollowPreset()
+    }
+
+    // MARK: - MQTT publish helpers
+
+    private func publishFollowMode() {
+        mqtt.publish(topic: Self.followModeTopic, payload: followMode.mqttPayload)
+    }
+
+    private func publishFollowPreset() {
+        mqtt.publish(topic: Self.followRangeTopic, payload: followPreset.mqttPayload)
+    }
+
     // MARK: - MQTT GPS publish (1 Hz)
 
     private func startMQTTPublishTimer() {
@@ -159,14 +208,13 @@ final class SensorManager: NSObject, ObservableObject {
         mqtt.publish(topic: Self.iosGPSTopic, payload: json)
     }
 
-    // MARK: - Robot GPS subscription handler
+    // MARK: - Incoming MQTT handlers
 
     private func handleRobotGPS(_ payload: String) {
         guard let data = payload.data(using: .utf8),
               let json = try? JSONSerialization.jsonObject(with: data) as? [String: Any],
               let lat  = json["lat"] as? Double,
               let lon  = json["lon"] as? Double else { return }
-
         let coord = CLLocationCoordinate2D(latitude: lat, longitude: lon)
         robotLocation = coord
         robotSpeed    = (json["speed_ms"] as? Double) ?? 0
@@ -174,6 +222,39 @@ final class SensorManager: NSObject, ObservableObject {
         updateDistance()
     }
 
+    private func handleUWBRange(_ payload: String) {
+        guard let data     = payload.data(using: .utf8),
+              let json     = try? JSONSerialization.jsonObject(with: data) as? [String: Any],
+              let anchorID = json["anchor_id"] as? String,
+              let rangeM   = json["range_m"] as? Double else { return }
+        uwbRanges[anchorID] = UWBRange(anchorID: anchorID,
+                                       rangeMetres: rangeM,
+                                       timestamp: Date())
+    }
+
+    private func handleUWBPosition(_ payload: String) {
+        guard let data = payload.data(using: .utf8),
+              let json = try? JSONSerialization.jsonObject(with: data) as? [String: Any],
+              let x   = json["x"] as? Double,
+              let y   = json["y"] as? Double,
+              let z   = json["z"] as? Double else { return }
+        uwbPosition = UWBPosition(x: x, y: y, z: z, timestamp: Date())
+        uwbActive   = true
+    }
+
+    // MARK: - UWB staleness watchdog
+
+    private func startUWBStalenessTimer() {
+        uwbStalenessTimer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { [weak self] _ in
+            guard let self else { return }
+            let cutoff = Date().addingTimeInterval(-Self.uwbStaleSeconds)
+            if let pos = self.uwbPosition, pos.timestamp < cutoff {
+                self.uwbActive = false
+            }
+            self.uwbRanges = self.uwbRanges.filter { $0.value.timestamp > cutoff }
+        }
+    }
+
     // MARK: - Breadcrumbs + distance
 
     private func appendBreadcrumb(_ coord: CLLocationCoordinate2D,
@@ -208,7 +289,7 @@ final class SensorManager: NSObject, ObservableObject {
 
     private func startIMU() {
         guard motionManager.isDeviceMotionAvailable else { return }
-        motionManager.deviceMotionUpdateInterval = 1.0 / 100.0  // 100 Hz
+        motionManager.deviceMotionUpdateInterval = 1.0 / 100.0
         motionManager.startDeviceMotionUpdates(to: .main) { [weak self] motion, _ in
             guard let self, let motion else { return }
             self.recordEvent(in: &self.imuCounts)
@@ -290,7 +371,7 @@ extension SensorManager: CLLocationManagerDelegate {
                 "latitude":           loc.coordinate.latitude,
                 "longitude":          loc.coordinate.longitude,
                 "altitude":           loc.altitude,
-                "horizontalAccuracy":loc.horizontalAccuracy,
+                "horizontalAccuracy": loc.horizontalAccuracy,
                 "verticalAccuracy":   loc.verticalAccuracy,
                 "speed":              loc.speed,
                 "speedAccuracy":      loc.speedAccuracy,

SulTee/SulTee/UWBModels.swift

@@ -0,0 +1,51 @@
+import Foundation
+
+// MARK: - Follow mode
+
+enum FollowMode: String, CaseIterable, Identifiable {
+    case gps = "GPS"
+    case uwb = "UWB"
+    var id: String { rawValue }
+
+    var mqttPayload: String {
+        "{\"mode\":\"\(rawValue.lowercased())\"}"
+    }
+}
+
+// MARK: - Follow range preset
+
+enum FollowPreset: String, CaseIterable, Identifiable {
+    case close  = "Close"
+    case medium = "Medium"
+    case far    = "Far"
+    var id: String { rawValue }
+
+    var metres: Double {
+        switch self {
+        case .close:  return 1.5
+        case .medium: return 3.0
+        case .far:    return 5.0
+        }
+    }
+
+    var mqttPayload: String {
+        let d: [String: Any] = ["range_m": metres, "preset": rawValue.lowercased()]
+        guard let data = try? JSONSerialization.data(withJSONObject: d),
+              let str  = String(data: data, encoding: .utf8) else { return "{}" }
+        return str
+    }
+}
+
+// MARK: - UWB data types
+
+struct UWBPosition {
+    let x, y, z: Double
+    let timestamp: Date
+}
+
+struct UWBRange: Identifiable {
+    let anchorID: String
+    let rangeMetres: Double
+    let timestamp: Date
+    var id: String { anchorID }
+}