GPS-Denied Navigator

Where am I

No session

Start a session in the Course tab.

Start / resume

Last known position (lat, lon — or MGRS)

Accuracy of that position (m, 1σ)

Moving by

Magnetic declination (° east +, blank = built-in WMM table)

Planned route

Waypoints, one per line: name, lat, lon — or name, MGRS

Corridor half-width (m)

Arrival radius (m)

Map (offline, no tiles needed)

Estimate + 95% ellipseRouteKnown pointsFixes appliedRejected

Next best fix

Start a session to see recommendations.

Automatic (phone sensors)

Counts your steps and reads your heading. Hold the phone flat in front of you, top pointing where you walk. The navigator learns your stride and compass error from every fix.

Stride calibration

Walk a known distance (m)

Manual leg (compass + pace count)

Heading (°)

Reference

Distance (m)

or pace count

pace length (m)

Sight a known point with the camera

Point the camera at a known landmark. Green markers show where known points SHOULD be from the current estimate. Tap the landmark itself. Two or more landmarks about 60–120° apart give a position. One landmark plus a range also works.

Landmark

Bearing accuracy (° 1σ)

Range by known height

Object height (m)

Resection from collected sightings

None collected.

Solve compass error too (needs 3+ landmarks)

Calibrate

Compass: center the crosshair on the Sun (use a filter, or just its glare edge) or on Polaris, then press. Field of view: tap two known points in one frame from a known position.

Camera horizontal FOV, long side (°)

Polaris — latitude & true north

Measured altitude Hs (°)

Time (UTC)

Horizon

Height of eye (m)

Accuracy (′ 1σ)

Star / Sun fix

Body

Hs (°)

Time UTC

Horizon

Height of eye (m)

Accuracy (′)

Limb (Sun)

Sky now (from current estimate)

Add a known point

Label Position (lat, lon — or MGRS)

Accuracy (m 1σ)

Elevation (m, optional)

Share & sync

Import points (JSON file)

Known points on this device

Every input and what the navigator did with it

Import session

Self-test (runs on this device, offline)

Recomputes 38 U.S. Naval Observatory almanac values and known-answer geometry checks. Full measured results: docs/navcore/PROOF.md; server copy: /api/navcore/selftest.

How this navigator works

One estimate of where you are, with an honest error ellipse. Walking moves it and grows the ellipse. Every sighting of a known point, every star or Polaris line, and every map/terrain fix pulls it toward the truth and shrinks the ellipse, weighted by how good that observation is. It also learns your compass error and your stride length from those fixes. If an observation doesn't fit, it's rejected and shown in the Log. It is never silently accepted. The navigator never resets itself; only an operator can, and that is logged too.

Evidence labels: OBSERVED = a real measurement reduced by the math below. MODELED = dead reckoning only, no fix yet. SYNTHETIC = demo data, never used here.

API for other systems: /api/navcore/contract · Source: shared/navcore/ · Docs: docs/navcore/README.md