Elevation data optimization settings - and how the process works?

Dear Locus team,

Please explain me the following, regarding elevation data optimization settings AND how the process works, how the calculation steps relate to each other.

My baseline: I have a phone with barometric pressure sensor (and obviously I turn on the use of its data), and I have SRTM 1” .hgt DEM data files in the /Locus/SRTM/ folder.

I want a settings combo that works well, even in steep/deep gorges and small but high peaks with sudden/vertical walls.

Revise the following points, tell me if it is true – or rather rewrite it to fully comply with the real working logic of Locus Map 4.

Please, also tell me which combination of the relevant settings works best.

1. How “Elevation data” really works

The “Elevation data” setting in Altitude Manager refers only to how GPS altitude is treated. It decides what to do with GPS-reported heights before anything else (barometer, filters) is applied.

Don’t use → raw GPS altitude.

Optimize GPS values → Locus blends GPS with DEM (.hgt) data to smooth GPS noise. This has nothing to do with barometer.

Replace GPS values → Locus discards GPS altitude entirely and substitutes DEM height (from .hgt). Again, no barometer here.

This step is purely about GPS vs. DEM. The barometer is handled later.

2. Where does the barometer come in?

The barometric pressure sensor is handled separately, and only if you enable it under:

Settings → GPS & sensors → Altitude manager → Use pressure sensor.

When enabled, Locus takes your chosen GPS/DEM altitude (from step 1 above), and then:

Uses that as a baseline for barometer calibration (to prevent drift).

The actual altitude values recorded to trackpoints come mainly from the barometer, corrected at intervals against the DEM (and/or GPS).

So the pipeline looks like this:

1. GPS altitude arrives → (apply Optimize/Replace/Don’t use) → “corrected GPS altitude”.

2. If barometer enabled → corrected GPS/DEM altitude used to calibrate barometer baseline.

3. Barometer altitude values drive the recorded track (fine detail).

4. Altitude filter applied to smooth noise from GPS/baro if selected.

5. Final altitude written into track log.

3. About the Altitude filter

Even the barometer has noise — it can jump ±0.5–1 m from tiny pressure fluctuations (wind gusts, breathing near sensor hole, etc.).

The light filter smooths these tiny jitters without destroying real elevation changes.

Medium/Heavy filters will start to “blur” sharp gorges/cliffs — not what you want.

👉 With 1″ DEM + barometer, a light filter is still useful. Otherwise your track profile may look unnaturally “nervous,” with ±1–2 m wiggles on flat terrain.

4. Do these two settings interact?

Yes, but sequentially, not simultaneously.

Elevation data (Optimize/Replace) → determines how GPS altitudes are pre-processed (before barometer calibration).

Barometer → gives relative altitude detail, calibrated against that baseline.

Altitude filter → applies at the very end, cleaning up noise from both GPS and barometer.

So:

They don’t “mix” DEM and barometer at the same step.

But they are chained: GPS/DEM baseline → baro → filter.

✅ Best setup for phone with barometer + 1″ DEM data downloaded:

1. Use pressure sensor → ON

2. Elevation data → Optimize GPS values. Because you don’t want DEM to replace everything (too smooth in gorges), but you do want DEM to stabilize GPS.

3. Altitude filter → Light filter. To remove micro-jitters but keep sharp vertical walls intact.

4. Automatic barometer calibration → ON (every 5–10 min or after X m of climb).

5. Post-processing (Fill altitude / Replace with DEM) → OFF, unless rescuing a corrupted track.

👉 Result: You’ll get realistic gorge walls, smooth long climbs, and no drift from weather pressure changes.