Marine Barometer

Classic-style Barometer, Altimeter, Logger, and Pressure Trend Graph for Android

Welcome

Marine Barometer turns an Android phone or tablet with a built-in pressure sensor into a simple, readable weather instrument. It combines a sea-level-corrected barometer, an aircraft-style altimeter, a reference needle, optional pressure logging, and a strip-chart pressure trend graph.

Current Version: 1.5.19 beta

Release Date: June 8, 2026

Highlights

• Live barometer: Sea-level corrected pressure shown in hPa or inHg.
• Altimeter: Aircraft-style three-pointer display with QNH, QFE, and QNE reference modes.
• LINK/UNLINK control: Let the app manage the altimeter reference, or set it manually.
• Reference needle: Mark the current pressure and watch the trend rise or fall.
• Log + Graph: Record pressure data and view a truthful pressure trend graph.
• Setup page: Log-folder selection and folder help are grouped under MENU → SETUP.
• Pressure-sensor calibration: Corrects phone sensor offset using known reference information.
• Offline ordinary use: Once set up and calibrated, no internet connection is needed for normal barometer use.

Altimeter

• SET: Change altimeter mode
• QNH: Reads altitude above sea level when set to local barometer reading.
• QFE: Reads altitude above current location when set to local barometer reading.
• QNE: Set the barometer to 29.92 inches Hg(1013.25 mb) for high level flight.
• Link/Unlink. Links the altimeter to the current Marine Barometer reading.
• LOG: Logs and Graphs the last 12 hours of barometer readings
• Start/Stop Log+Graph: Turns logging and graphing on or off.
• Open Log File: Opens the log file in the MarineBarometer folder on your device.
• ALT: Switches back to Altimeter display.
• Graph: Switches to graph display.

In "Linked" mode the altimeter setting is linked to the barometer reading. In "QFE" mode the altimeter should always read zero when the presure sensor on your phone or tablet is calibrated, and if the device is at the elevation that it was calibrated for - which is usually its home base. A ±50 foot error is not cause for alarm, but you should step through the calibration process if the error is greater than ±100 feet.

Marine Barometer is part of the Virtual Cockpit family, but it is also useful on its own at home, on a boat, in an RV, at a campsite, or while travelling.

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Download

Current Version: 1.5.19 beta

Click the icon below to download the APK installation file:

Website maintenance note: The download link above expects the APK file to be named Marine_Barometer_v1.5.18.apk and stored in the same folder as this page.

Installation Steps

1. Tap the download link above.
2. Open your Downloads folder and tap the APK file.
3. If prompted, allow installation from this source.
4. Let Google Play Protect scan the file.
5. Follow the prompts to complete installation.

Important: This app needs a phone or tablet with a built-in barometric pressure sensor. Many modern Android devices have one, but not all do. The app is intended for Android 6.0 or higher.

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Screens

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Instructions

Quick Start

1. Install the app.
2. Confirm that your device has a pressure sensor.
3. Open MENU → SETUP and choose or reauthorize the log folder if you want to use Log + Graph.
4. Find the elevation of your home, marina, campsite, or other reference location.
5. Look up the current local sea-level pressure from a reliable nearby weather report.
6. Open MENU → CALIBRATE and enter the known elevation and known pressure.
7. Use SET to choose the altimeter reference mode and setting.

Everyday Use

• Barometer dial: Shows the current sea-level corrected pressure.
• Reference needle: Press the barometer center knob to park the reference needle at the current reading. Later, compare the live needle against the reference needle to see whether pressure has risen or fallen.
• Altimeter dial: Shows indicated altitude based on the current altimeter reference setting.
• UNITS button: Switches between hPa and inHg.
• SET button: Opens the altimeter reference dialog.
• MENU button: Opens setup, calibration, help, theory, and other pages.

Altimeter Reference Modes

• QNH: The altimeter reference is a sea-level pressure setting. This is the normal aviation-style altimeter setting.
• QFE: The altimeter reference is a station or reference-location pressure. When the pressure matches the QFE reference, the altimeter reads zero relative to that reference point.
• QNE: The altimeter reference is set to the standard pressure setting of 1013.25 hPa (29.92 inHg).
• UNLINKED: You control the altimeter reference manually.
• LINKED: The app computes the effective altimeter reference from the selected mode and the available reference information. LINKED is not available in QNE mode because QNE is, by definition, the fixed standard pressure setting: 1013.25 hPa (29.92 inHg).

Set Altimeter Dialog

• QNH/QFE: The main mode toggle selects whether the setting box contains a sea-level QNH value or a station/reference-location QFE value.
• LINKED/UNLINKED: LINKED lets the app manage the reference from the selected mode and available reference information; UNLINKED lets you enter the value yourself.
• QNE: The QNE button loads the standard pressure setting, forces UNLINKED, and waits for you to press ENTER before the setting is committed.
• ENTER: Commits the value currently shown in the setting box.
• User setting: If you touch or edit the setting box, the value is treated as a User QNH Setting or User QFE Setting, depending on the selected mode.

Important: A QFE drift or calibration check is meaningful only when the reference pressure comes from an independent source, and if the reference elevation entered in the app is correct. If the app simply copies its own live pressure back into the altimeter reference, that is a convenience setting, not proof that the phone pressure sensor is calibrated.

A Practical Routine

1. In the morning, reset the reference needle to the current pressure.
2. Check the app again a few hours later.
3. If the live needle is above the reference needle, pressure has risen.
4. If the live needle is below the reference needle, pressure has fallen.
5. Use the graph when you want a longer pressure-trend view.

Notes

• Calibration removes sensor offset. It does not turn a phone into a laboratory instrument.
• Room temperature, sunlight on the phone, and abrupt movement can cause small short-term changes.
• For best results, calibrate where you know both the elevation and the current local pressure.
• Changing the altimeter setting should affect the altimeter only, not the barometer reading.
• Pressure values are displayed to two decimal places in both hPa and inHg.

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Logging & Graph

Marine Barometer can record pressure data and display a pressure trend graph while Log + Graph is running.

Setup

1. Open MENU → SETUP.
2. Choose or reauthorize the log folder.
3. Return to the LOG page.
4. Start Log + Graph only after the folder status is ready.

The LOG page now focuses on folder status and Start/Stop controls. Folder selection and folder help belong on the SETUP page.

Graph Truthfulness

• The graph displays the last 12 hours of data, if available.
• The graph does not draw a line forward to the current time without a real sample.
• The graph breaks plotted lines across large sample gaps.
• The graph shows the last-sample age so stale data is visible.
• Saved graph history is restored only when the pressure context matches.

Current CSV Files

• pressure_log_v3.csv — main pressure log.
• pressure_graph_v3.csv — graph history and diagnostics.
• calibration_history.csv — calibration-event history.

The current v3 pressure and graph files include altimeter reference fields, including QNH/QFE/QNE mode, LINK/UNLINK state, effective reference pressure, QNH source pressure, and QFE reference pressure.

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Theory

What the pressure sensor measures
Your phone's pressure sensor measures the air pressure where the phone is sitting. That is local station pressure, not sea-level pressure.

Why elevation matters
Air pressure decreases with height. To compare pressure at different places, weather services correct local pressure to sea-level pressure. Marine Barometer does the same thing after you tell it the elevation of your location.

What calibration does
Calibration estimates the pressure-sensor error and stores a correction. After calibration, the app uses the corrected pressure plus the known reference elevation to compute the live barometer reading. The normal calibration path is offset-first; slope changes are advanced and should require stronger evidence.

What the altimeter does
The altimeter does not know your true altitude by magic. It converts pressure into indicated altitude using the barometric reference setting. If that setting is wrong, the indicated altitude will be wrong too.

QNH and QFE
QNH is a sea-level pressure setting. QFE is a station or reference-location pressure setting. Marine Barometer exposes both modes so the altimeter reference is visible and traceable instead of hidden inside one setting number.

QNE
QNE is the standard pressure setting of 1013.25 hPa (29.92 inHg). It is used at high altitudes above the transition level, typically 3,000 to 18,000 ft depending on the country and airport, to provide a standardized reference that helps aircraft maintain safe vertical separation regardless of local pressure changes.

What the reference needle does
The reference needle is a trend marker. It does not affect the measurement. It simply remembers an older pressure so you can compare then versus now at a glance.

Reading the trend
A rising barometer often goes with improving weather. A falling barometer often goes with unsettled weather. The size and speed of the change matter, and local geography still matters, so treat the app as one useful clue, not the whole forecast.

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Finding Your Elevation

To calibrate properly, you need the elevation of the place where the phone is sitting.

Recommended Sources

• Canada: NRCan Toporama — good for Canadian users and official mapping.
• Worldwide quick lookup: Free Map Tools Elevation Finder — simple click-on-map tool with latitude, longitude, and current-location options.
• Also useful: topographic-map.com (Canada).
• US mirror: topographic-map.com (US English).

Using topographic-map.com

• Type a place name in the search box, or use the geolocate button near the search bar.
• Zoom in until the pointer is over your home, dock, campsite, or launch point.
• Use the elevation at that spot as your reference elevation.

Example link to Calgary Airport (YYC)
Click on the link below for an example based on the instructions above for topographic-map.com.

Calgary Airport (YYC) Elevation

The easiest way to make a similar link is to open a nearby place once in the browser, then edit the center, zoom, and popup values in the address bar.

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History

This table summarizes the main public/test milestones. Some internal corrective spins may have had narrower code-only changes.

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