01 / Begin
A reading begins when you enter.
The instruments start their required sensors automatically. There is no ordinary Start button. On a cold launch, a simple black welcome screen shows the wordmark and “Find your direction. Help others find theirs” for two visible seconds; returning from the background does not repeat it.
Choose Compass, Level, Angle or Ride Panel from the tool grid. Swipe vertically across the instrument area to change tool, or use the grid / keyboard Up and Down arrows. Scrollable content, sliders and sheets keep their own gestures. This native build offers four themes — Origin, Classic, Modern and Tech — chosen from the palette icon in the top bar or in Settings. Switching is instant and needs no restart; a theme changes appearance only. Quick start: open the tool grid → Compass; choose Rose and Magnetic; wait for a valid heading. Then choose Level → Surface, or hold the phone on an edge and choose Bar. Bicycle g: Ride Panel → Calibrate g → mount style → Calibrate mount while parked.
02 / Compass
Which way is the phone pointing?
The heading is measured from north clockwise using the top of the phone as the reference: 0° N, 90° E, 180° S and 270° W. A reading such as 136° SE means the phone top points southeast. The tiny concentric bubble indicates tilt; a centred bubble helps you hold the phone level.
Rose: the N/E/S/W dial rotates with the world; its N points north and the fixed top mark represents your phone. Needle: the ticks remain fixed to your phone and the highlighted north pointer points north; the fixed ticks have no N/E/S/W letters. The number is still your heading, not the tick under the north pointer. Compass and Level use lining, tabular system numerals with a stable size for the available width. Compass gives one system haptic when a fresh heading enters within 2° of north or south under the selected magnetic/true reference; leaving by at least 5° rearms it, with at least one second between pulses. Covered sheets, other pages, background, stale readings, Calm, Reduce motion, and the existing session haptics switch suppress feedback. This is an alignment cue, not an accuracy guarantee; check actual feedback on your device.
Reference / Magnetic or True
Two definitions of north.
Magnetic uses the local magnetic field. True uses geographic north, with a location-based correction supplied by iOS. Their difference varies with your location. True requires a usable location and heading; an unavailable True reading is shown as unknown, never silently replaced by Magnetic.
For a steady bearing, move away from magnets, a magnetic case and large metal objects, hold level and let the sensor settle. Display smoothing improves readability; it does not guarantee accuracy. Compass help explains the two display modes.
Location / Best effort
A place, when it is available.
The dial and heading stay dominant. Bottom menus choose Rose / Needle and Magnetic / True; the location icon toggles coordinates, the mountain opens Environment, and the details icon opens quality, age, format, copy, manual conversion and calibration guidance. Decimal latitude and longitude share a line; DMS and large text wrap when needed. Unknown or stale data keeps the same space, never fake zero. The address is bold and limited to two lines on the main view; Details shows the full available text.
Detailed address in Settings is off by default: city or region remains the default. Enable it for Apple best-effort street/full-address lookup. This changes the address display, not location accuracy or background permissions. Unavailable street detail falls back to locality. A long detailed label may be omitted from a saved record; valid saved coordinates remain. Historical records never update their saved label.
Free foundation / Coordinates
Your choice, your position.
Compass Show location data is off by default. Enable it to read the foreground latitude, longitude, system estimated horizontal uncertainty and sample age; first enable explains the purpose before requesting permission. Coordinates disappear immediately on off, stale fix, background, or leaving Compass. True heading, Ride Panel, expanded GPS altitude or a current map can independently use the shared GPS. Settings lists these consumers; activity is not a promise of a fix. Magnetic Compass alone does not start GPS. Heading uncertainty is the system estimate, not an invented magnetic-interference detector; follow the free calibration guide.
Coordinate converter works without GPS: choose Decimal or DMS, enter latitude then longitude, exchange the inputs to swap axes and revalidate, or Clear. Degrees/minutes/seconds and hemisphere are separate fields. Copy Decimal and Copy DMS are deliberate actions with success or failure feedback; nothing reads the clipboard or keeps conversion history. More digits do not imply more accuracy. Saved records have Location details for immutable coordinates, system uncertainty, fix time and save time, plus explicit copy and historical Map. Legacy records never acquire today’s location; default record sharing still excludes location. See Location for place names and optional detailed addresses.
Map / Apple MapKit
See the place without leaving Northkind.
Tap the bold place name in Compass or Ride Panel. When no place name is available, the compact Map entry still opens a separate map page. Pan and zoom inside the map; Close returns to your instrument. Recenter needs a fresh valid GPS fix. A stale or unavailable fix removes the current-position marker rather than showing an old position as current.
Apple MapKit loads map data using network services. Map loading and GPS availability are shown separately; Retry map is offered after a load error. Location already authorised uses the same native GPS service as the instruments. Enable location is an explicit permission action when needed. Live coordinates are in memory only, visible to the opted-in foreground Compass; a location snapshot enters local records only when you explicitly save it, and default sharing omits it. A saved record with a location shows a bold place and a Map action that opens its historical point; that saved map never follows current GPS or expires as current. Closing the map releases its extra location demand, and backgrounding clears the live position marker. The browser preview shows an honest unsupported message, not a simulated map.
Compass / Environment
Height and pressure, with their sources.
Tap the mountain icon (Environment) beside Rose / Needle to expand; the section starts closed. Altitude first uses a fresh authorised GPS fix with valid vertical uncertainty; if GPS altitude is unavailable and the device supports it, a fresh CoreMotion absolute-altitude estimate is used. The source and estimated uncertainty are shown. Below-sea-level altitude is valid. Unknown or expired values remain —.
Device pressure is the phone barometer reading in hPa, not weather-service sea-level pressure. Relative height is in metres from this sampling session or the last Zero relative height action; zero is available only with a valid fresh reading. Closing the section, changing tool or tab, or entering background stops the added altimeter sampling. Returning while still expanded starts a new session and resets the relative baseline. Expansion may request Motion & Fitness permission but never automatically requests new GPS permission. Environment values are not added to existing heading records or shares.
Environment / Units + calibration
Two altitude sources, clearly separated.
Compass → mountain opens Environment. Native altitude is GPS or supported CoreMotion absolute altitude with its own uncertainty and freshness. Device pressure is measured at the phone, not sea-level pressure. Barometric estimated altitude is calculated from pressure and QNH; it is shown separately from native altitude. Select m / ft and hPa / mmHg / inHg in Settings.
Tap Calibrate Altitude (QNH), enter a known altitude in the displayed unit and apply only with a fresh pressure sample. Reset uses standard atmosphere 1013.25 hPa; it is not a weather-service QNH. Calibration does not modify native altitude or create a false jump in accumulated ascent/descent. Session ascent/descent and pressure trends are observational estimates; resetting the session clears its statistics. Background/closing clears the relative-height baseline; missing hardware or stale samples show —.
03 / Level
A surface, or a long straight edge.
Surface is for a phone lying on a surface: centre the bubble and read surface deviation, with roll and pitch shown separately. Bar is a long spirit level for a phone held on its edge; centre the bubble to make the inferred down-facing edge horizontal.
Set zero uses the current valid reading as your relative baseline. Reset zero restores the absolute reference. Bar zero belongs to the current physical edge, so turning the phone does not apply another edge’s zero. Unknown data never means level.
Automatic edge / Angle + Bar
The edge facing down becomes the reference.
Hold the phone with its screen approximately vertical and rest the desired edge on the object. Gravity selects bottom, left, right or top automatically, and the instrument stage rotates to read along that edge. Automatic selection is available for ordinary use; target alignment fixes the current measuring edge, and clearing the target restores the prior selection. See Target alignment.
This infers the down-facing edge, not physical contact. Near flat, gravity cannot distinguish a down edge: the app shows Flat · no down edge and no edge angle. Use Surface mode for a flat phone. Near a corner, a small switching margin reduces repeated flips. A positive angle means the displayed edge direction rises; negative means it falls.
04 / Angle
Measure inclination, not the phone’s whole pose.
Angle reads the inferred edge’s physical angle to horizontal, or the difference from a reference you set. Set reference captures the current valid edge angle; Reset removes it. The reference is associated with that edge. A flat phone has no unique down edge and therefore no valid edge angle.
Slope expresses the relative inclination as 100 × tan(angle) %. 45° is 100%, not 45%. At ±90° slope is undefined and shown as Vertical. Protractor is a separate manual 0–180° slider: it uses no sensor and saved readings are explicitly Manual. It does not measure an angle from an image.
Angle / Target alignment
Choose a target, keep one edge.
In Angle or Slope, open Target angle. Choose 0°, 30°, 45°, 60°, 90°, or enter degrees / slope %. Slope converts through atan(percent / 100): 100% is 45°. Setting a target fixes the current measurement edge so turning past an automatic-edge boundary does not change the reference. Read the fixed-edge notice; Clear target restores the previous edge selection. Changing mode, edge or reference also clears the target; custom values must be reachable relative to the current reference. Set the phone upright first: a flat phone has no valid edge.
The indicator shows signed Δ and three states: outside 3°, approaching within 3°, aligned within ±0.5°. These are software tolerance windows, not a sensor accuracy promise. Target haptics are a session-only choice; enable or disable them and use the test vibration action before relying on them. Reduce motion / Calm can suppress feedback. A fresh transition into alignment triggers one system haptic; leaving and returning can trigger again. Automatic alignment and test vibration share a cooldown of at least one second. Actual vibration depends on device and system settings; the app does not read or guarantee silent-mode behaviour.
Level + Angle / Experiments
Observe apparent forces safely.
Level → Elevator: keep the phone still at rest and calibrate 1.0g, then observe apparent gravity, net vertical acceleration and session extrema. Hold freezes the captured values; Resume returns to live data. Reset tare and extrema when starting a new experiment. Upward acceleration can increase apparent weight; downward acceleration can reduce it. This is an educational sensor model, not an elevator safety monitor.
Angle → Pendulum: observe the virtual bob and horizontal acceleration; no physical pendulum or additional hardware is required. Switch g / m/s², calibrate the stationary zero and reset it when the setup changes. Hold freezes a valid snapshot. Stale or unavailable motion stays unknown. Do not create a free-fall experiment, handle the phone while riding, or use either experiment as an emergency prediction.
05 / Ride Panel
Speed first. Motion in context.
Ride Panel is Experimental: auxiliary GPS speed and bicycle-motion reference only. Read the parked-and-mounted safety notice first. Never operate controls while riding. The 90° button rotates content, not the system orientation lock. Stop in a safe place before using any controls. Securely mount the phone with its screen facing the rider. GPS speed is an auxiliary reference; no bicycle speedometer is assumed. Bicycle lean and vibration affect Forward/Lateral g, which cannot indicate safe cornering or traction.
GPS speed uses the iOS location speed reading; switch km/h or mph in the bottom dock. A real valid zero may be displayed when stopped; missing, stale or invalid speed is —. GPS acquisition can take time, especially indoors. There is no promised response time or precision. Scenes Cruise / Acceleration / Braking / Cornering focus the relevant readings; they do not generate data.
Mount / Before bicycle g
Park. Mount. Calibrate.
Forward and Lateral are unavailable until stationary mount calibration succeeds. Tap Calibrate g in the bottom dock to open Sensors & mount. Select Flat mount (phone top points forward) or Upright mount (screen faces the rider). Secure the phone in that pose, keep it still and choose Calibrate mount.
Calibration requires a short sequence of fresh stationary motion samples; motion or unsuitable gravity can reject it. Recalibrate after moving the mount, a significant orientation change or a lifecycle reset. Forward is longitudinal acceleration / braking; Lateral is side acceleration, in g. The app cannot discover the bicycle’s direction from gravity alone. An uncalibrated — is intentional, not a sensor zero. Stop in a safe place before using any controls. Securely mount the phone with its screen facing the rider. GPS speed is an auxiliary reference; no bicycle speedometer is assumed. Bicycle lean and vibration affect Forward/Lateral g, which cannot indicate safe cornering or traction.
06 / Records
Keep the moment you saw.
Tap the save icon on a valid reading. The instrument image and draft freeze at that instant while you add an optional note; background acquisition can continue. Save commits that captured value, not a later changing reading. Cancel returns to the live instrument. Unknown or stale readings cannot be saved.
Records live on this device when storage is available. Open Records to search by keyword, filter by tags, and toggle favorites. Tap Edit to customize title, note and tags. Select mode allows batch selection, bulk deletion with confirmation, and professional export. Export supports CSV attachments and PNG reports; location coordinates remain strictly gated behind an explicit opt-in and are omitted by default. Notes and tags you create stay on your device. Share an observation shows the exact PNG image pages. Share image opens the iOS share sheet; Copy text copies the full original text. Long content is paginated. If image preparation fails or exceeds its capacity, copy the text instead. Saved location fields and scene photos are not added automatically; review private content you typed into notes. Check actual delivery in the receiving app.
Records / Export
Review first, share once.
Records → search narrows keywords; tag filters and favorites help organise entries. Edit changes title, note and tags without replacing the frozen measurement or saved location. Select enables batch export or confirmed deletion. Export → Share CSV produces a CSV attachment on supported native devices; Copy CSV puts its text on the clipboard. CSV uses UTF-8 BOM and standard quoting for multilingual fields.
Share PNG Report creates fixed 900 × 1200 report pages with wrapped text; a batch can share multiple PNGs, up to 50 pages. Oversized exports fail clearly: reduce the selection. Browser previews cannot share PNG. Locations and place names are excluded by default; Include location is an explicit choice for one operation and resets afterwards. Cancel or failure preserves the sheet and reports the result. Report headings, tool names and CSV column names use English; your titles, notes and tags retain the text you entered. Report colours follow the active theme. Notes may contain your own private text: review before exporting.
Records / Location photos
A photo of the frozen reading.
Opening the save-reading sheet automatically freezes the available valid location snapshot. When that snapshot is present, tap Take photo. Camera access is requested only after your action. If permission is denied, the camera is unavailable, or the operation is cancelled, no successful capture is assumed; you can still save the reading without a photo. The attached image is annotated with the frozen save-time location information: address/place information, coordinates, location-fix time, photo-capture time, the reading and available parameters. An unavailable address or parameter must remain identified as unavailable; it is never replaced by a fabricated address or zero. The coordinates refer to the frozen location fix, not necessarily where the phone was when the shutter was pressed. Check the two timestamps when the photo is taken later.
Use View photo in Records to inspect the image; use Remove photo before saving to detach it. Changing a record's title, notes or tags does not rewrite the original photo annotation. Photos are managed in this app's local storage and are not automatically added to the system photo library. Existing CSV, report images and record text sharing continue to exclude these attached photos. Deleting a record, batch deletion or record-retention cleanup also schedules associated photo cleanup. If a cleanup warning appears, Retry photo cleanup completes the pending local operation. A reading may already be durably saved while unrelated photo cleanup remains pending; these are separate outcomes. Copies or screenshots saved outside the app are not removed by deleting the original record.
Records / Foreground tracks
Record explicitly, continue explicitly.
Open Walking and cycling tracks from Records. Choose Location permission when needed, then explicitly select Start walking or Start cycling. Permission alone does not begin a track. Location Services or permission failures are shown; missing, stale, out-of-order, inaccurate or implausibly jumping fixes are not silently saved as zero readings. V1 records only while the app is in the foreground. Locking the screen, moving to the background or leaving this page pauses recording and releases the track's location consumer. Returning does not resume it: use Continue. This is not continuous background tracking. Use Pause, Continue and Finish track as needed. Pauses and missing intervals remain separate route segments; the app never fills a gap with invented movement.
After interruption, open the saved session or Recover saved segments. Only the durable segments can be recovered; the session remains paused until you explicitly continue. Storage failures retain already saved data and show retry/recovery status. Reaching a protective capacity limit pauses or refuses new recording without silently deleting old tracks. Finish or delete the current unfinished session before opening another one. On iPhone, Geographic map shows the segmented route using the native map. Offline map tiles may be unavailable. Local route overview provides a coordinate-based view without a fetched basemap; north is up, the start is a green ring and the end a red square. Drag/pinch or use the pan, zoom and reset buttons. Route snapshots refresh about every five seconds; saved point counts update promptly. GPS distance is an estimate, not certified measurement. Viewing a saved route does not start location recording.
Tracks / Privacy + sharing
Preview the route you will share.
Pause or finish a nonempty route, then select Preview track sharing. By default, all points within 200 m of the original first and last fixes are excluded, including any later revisit to those areas. Removed intervals and original pauses remain disconnected. Preview the actual output before choosing Share route image or Export GPX file; both use the same trimmed route, not the hidden original endpoints. The source track stays unchanged. If trimming leaves no points, neither image nor GPX can be exported. Including the full route requires a separate active confirmation because precise locations can reveal home or other private places. Cropping reduces exposure; the remaining route and GPX timestamps may still reveal sensitive information. GPX retains time and valid available elevation; unavailable elevation is omitted. Route sharing does not attach location photos or upload the route to a Northkind server.
Use the system share sheet to choose WeChat if it is available. The image is intended for ordinary image viewing; GPX is a data-exchange file and requires a compatible receiver. A completed share sheet does not prove the recipient received or opened anything. Actual WeChat reception, image clarity and the receiving app's GPX support must be checked on physical devices. V1 has no interactive web link or mini-program viewer.
07 / Settings
Make the view your own.
Open the tune icon for Settings. Language supports System, English, 日本語, 简体中文 and 繁體中文. System follows the supported device language; other languages fall back to English. A manual choice is saved in the existing on-device settings configuration and can be changed back to System.
Speed units, Larger readings, High contrast and Reduce motion are available. Larger system text is respected; unusually short screens may scroll the reading area while controls remain accessible. Themes are Origin, Classic, Modern and Tech. The Northkind page introduces the product, our promises and FREE / PRO features to everyone. FREE will always remain ad-free. PRO requires a verified Apple purchase. Settings provides purchase and restore actions; availability and price come from Apple. Before release, use the separate FREE/PRO testing guide. FREE includes Origin only. Classic, Modern and Tech, Ride Panel, and Walking and cycling Tracks belong to PRO. PRO actions require verified purchase entitlement; unverified or missing entitlement stays FREE. PRO appears on launch, home and settings after verification. Core accessibility, validity and privacy controls remain available. Photo and individual track-export entitlements remain undecided.
Settings / Accessibility + screen
Keep the display usable.
Keep screen awake offers System, Measuring (instrument page in foreground) and Always (default, all foreground pages). Backgrounding restores the system idle timer. Continuous light consumes battery; choose the smallest scope you need. Preferences are local. Four themes change appearance only and can be selected from the palette icon or Settings.
Use Larger readings, High contrast and Reduce motion; the interface also respects system text size. With VoiceOver, use labelled buttons and the tool picker as alternatives to swipes; scroll sheets and short screens to reach remaining actions. Test large text, contrast, vibration and VoiceOver on your own iPhone. This guide language is independent of the app and of iOS permission-dialog language.
Settings / Sensor quality
A quality estimate is not certification.
Open Sensor Quality & Diagnostics from Details / Settings. Inspect heading, motion and GPS status, sample age and update rate. Magnetic warnings indicate possible interference; move away from magnets and metal, hold steady and use calibration guidance. Sensor channels can be unavailable independently. Retry recovers a failed or stale stream; it cannot override a denied permission or install missing hardware.
Denied/restricted permission: choose Open Settings and review iOS permissions. Unsupported hardware: use supported modes instead. Old samples are never a valid zero; — cannot be saved as a measurement. Theme, smoothing and displayed decimal places do not improve sensor accuracy. A physical-device check remains necessary for real response time, vibration, position and mounting accuracy.
Permissions / Lifecycle
Foreground sensors, shared once.
All four tools use the same native sensor service: a shared motion manager and location manager, rather than four independent hardware sessions. Heading, motion and location availability are distinct. iOS can deny or restrict them; use the app’s Open Settings action and the appropriate iOS permissions. iOS permission dialogs and the iOS Settings app follow the system/app language rules chosen by iOS; the in-app language selector translates Northkind’s own interface, not operating-system dialogs.
The app does not collect background location. On backgrounding it stops acquisition and clears transient validity; returning to the tool restarts authorised sensors. Old values are never treated as fresh. A Retry action is for failures or stale streams, not an ordinary step before every use. A browser preview cannot validate iPhone sensors.
08 / Troubleshooting
Read the status before the number.
—: no valid current measurement; check the status, permission and whether the phone is flat in an edge mode. No edge / flat: lift the phone into an edge-measuring pose or choose Surface. g unavailable: open Calibrate g, select a mount and calibrate while parked. True unavailable: check location and heading. Place unavailable: allow time for a fresh fix and network lookup.
After a long pause: bring the app to the foreground; if data remains stale, use Retry and check iOS permissions. Jumping direction: avoid nearby magnets and let heading settle. Speed feels late: test outdoors; initial fixes may be cached, and GPS updates have their own cadence. Do not operate controls while riding. These tools assist observation; they do not replace a certified instrument or provide emergency predictions.
About these illustrations
UI references, not accuracy evidence.
Selected Flutter UI captures use deliberately simulated sensor values and an in-memory DemoStore. The current set was captured on iPhone 17 Pro / iOS 26.5 Simulator on 2026-10-04; these images do not prove a physical device, sensor accuracy, location or durable storage. See the local illustration manifest for source, review and hashes.
Legacy images with stale notices, wrong scenes or superseded interfaces are quarantined. Current captures preserve actual UI including some English labels. Native share delivery and physical-device verification remain separate checks. This manual follows current Flutter; frozen H5 Origin stays a historical reference. Only affected pre-Ride Panel, mount, settings-consumer, records and export screenshots are excluded pending new captures; inspected unaffected illustrations remain. Their files remain historical evidence.