What it is
The nav bar (top‑left of the chart) is your always‑on readout of the four numbers that matter most: COG, SOG, position (lat/lon), and charted depth under the boat. This module also covers follow mode, the compass, and the True/Magnetic north reference.
Want to see your position, heading, speed, and chart context working together on the water?
The 30-day free trial includes the complete experience, so you can evaluate SeaVectors with your own routes and equipment before deciding whether to subscribe.
- Download SeaVectors on the App Store
- Get SeaVectors on Google Play
- Not ready to install? Open the lightweight web chart for a quick preview.
The four readouts
| Field | Meaning | Source |
|---|---|---|
| COG | Course Over Ground, in degrees — the direction your boat is actually tracking. | GPS (or NMEA source). |
| SOG | Speed Over Ground, in knots — actual speed across the ground. | GPS (or NMEA source). |
| LAT / LON | Your position to 5 decimal places. | GPS. |
| Chart Depth | The charted depth beneath your boat, read from the ENC, in your chosen unit (ft/m). | ENC data, not a depth sounder. |
Important: "Chart Depth" is the charted depth from the ENC under your current position — it is not a live echo‑sounder reading. For live sounder depth, connect a NMEA source (module 06); it appears on the instrument panel's Depth widget.
The tracking control (location · follow · course‑up 3D)
A single tracking button cycles through three modes — tap it to move to the next:
| Mode | Icon | What it does |
|---|---|---|
| Locate | location outline | Your boat is shown, camera free — tap once to recenter on yourself, then pan freely. |
| Follow | filled location | The camera follows your boat, north‑up and flat. |
| Course‑up 3D | location + heading arrow | The camera follows your boat with course‑up rotation and a 3‑D tilt — the view turns so your heading is "up," great for pilotage and reading what's ahead. |
Tap again from Course‑up 3D to return to Locate. Panning the chart in a follow mode lets you look ahead; tap the button to snap back to your boat.
The compass & orientation
- The compass indicator shows the chart's current rotation.
- Tap it to reset to north‑up (and level out any tilt).
- Rotate the chart with two fingers when you prefer a course‑up or heads‑up look; the compass reflects it.
North reference: True vs Magnetic (Settings → Map Settings)
Choose how bearings are expressed:
- True (°T) — referenced to true north. The default and what charts are drawn to.
- Magnetic (°M) — referenced to magnetic north using your local declination, matching a magnetic compass on the boat.
Note: in Magnetic mode, bearings fall back to true (°T) when the local declination isn't known yet, or on devices without a magnetometer (e.g. Mac). Pick the one that matches how you steer.
Why it matters on the water
COG/SOG tell you where you're actually going and how fast — not where you're pointed — which is what you steer and plan by, especially in current. Keeping position and charted depth in view is your constant sanity check against the chart.
Tips
- Watch COG vs. heading in current or wind: the difference is your set/leeway.
- If SOG reads 0 and position is frozen, you've lost GPS — check permission and sky view.
- Match North reference to your primary steering compass so bearings agree.
Troubleshooting
- Blank COG/SOG/position → No GPS fix or location permission off (iOS Settings → Privacy → Location).
- Chart Depth blank or "—" → No ENC depth data at that exact point, or you're over land; it's charted data, not a sounder.
- Bearings look off by ~10–20° → You're likely comparing True and Magnetic; check the North reference setting.