What it does

Device Sensor Recorder captures one timestamped browser sensor record at a time. Each row can contain a sample ID, phone orientation, device location and an approximate solar elevation and azimuth, and the session can be exported as CSV.

Measurement scope

The app records raw browser orientation angles. It does not calibrate the phone to a leaf, derive a leaf-normal vector or certify measurement accuracy. Use a repeatable physical placement protocol and validate it for your experiment.

Before you start

• Use an HTTPS page on a phone or tablet that exposes motion/orientation sensors.
• Allow motion/orientation and location access when the browser asks. On iOS, the request must follow an explicit tap.
• Decide how the phone will be aligned with each sample and keep that alignment consistent.
• Location, altitude and orientation availability depend on the device and browser; unsupported values are shown as N/A or exported as empty cells.

Quick workflow

1. Open the app and tap Enable sensors.
2. Enter a value in Leaf or sample ID.
3. Hold the phone in the position defined by your sampling protocol.
4. Tap Capture Sample and wait for the location and orientation reading.
5. Review the new row, including location accuracy and both timestamps.
6. Repeat for additional samples, then tap Export CSV.

Controls & outputs

Control or panel	Actual behavior
Enable sensors	Requests motion/orientation permission and then requests the current location.
Leaf or sample ID	Adds an optional text identifier of up to 80 characters to the next record.
Capture Sample	Requests permissions if needed, obtains a fresh location, waits briefly for an orientation event and appends one row.
Refresh Location	Refreshes the location panel without creating a sample row.
Current orientation	Displays alpha, beta and gamma from the browser deviceorientation event.
Latest location	Displays latitude, longitude, optional altitude and browser-reported horizontal accuracy.
Export CSV	Downloads all rows recorded in the current page session.

The CSV columns are:

leafId,timestamp,latitude,longitude,altitude,geoAccuracy_m,alpha_deg,beta_deg,gamma_deg,inclination_deg,sunElevation_deg,sunAzimuth_deg,sensorTimestamp

How it works

• Orientation events are sampled through requestAnimationFrame; a capture uses the latest available event.
• Geolocation requests high accuracy with a 15-second timeout and no cached position.
• Solar declination and the equation of time come from the NOAA solar position algorithm (after Meeus). Apparent solar time is derived from the UTC instant, the longitude and the equation of time.
• inclination_deg is the angle between the phone's screen plane and the horizontal, arccos(cos β · cos γ). With the phone laid flat on a leaf blade it is the leaf inclination angle (0° horizontal, 90° vertical).
• A capture only uses an orientation reading received within the last second; if the sensor has stopped, the capture is refused instead of reusing an old value.
• Elevation is calculated from latitude, declination and hour angle. Azimuth is reported clockwise from north in the range 0–360°.
• CSV values are escaped, and text beginning with spreadsheet formula characters is prefixed before export.

The solar position has been validated against NREL SPA (160 cases, 1950–2090, latitudes ±65°): elevation agrees within 0.05° and azimuth within 0.1°. Elevation is geometric: atmospheric refraction, terrain horizon and site elevation are not applied.

Data, privacy & external services

Sensor values and captured rows remain in the current browser tab. The app does not send the dataset to an analysis service. Export creates a local CSV file through a temporary browser URL.

Motion and geolocation are protected browser capabilities. The browser and operating system decide whether the requests are available and what precision they return.

Limitations

Research use

• alpha is not guaranteed to be an absolute compass heading on every device.
• Sensor bias, phone cases, magnetic interference, device mounting and browser coordinate conventions can affect readings.
• GPS accuracy is not equivalent to survey accuracy, and altitude is frequently unavailable or noisy.
• Captured rows live only in page memory and are lost on refresh unless exported.
• Solar elevation may be negative when the sun is below the horizon.

Troubleshooting

Problem	What to check
Motion permission is denied	Enable motion/orientation access for this site in browser or system settings, then tap Enable sensors again.
No orientation reading arrives	Keep the phone awake, confirm that it has motion sensors and try a current mobile browser.
Location is unavailable	Enable location services, move to an area with a clearer signal and retry. The request can take up to 15 seconds.
Solar fields are empty	A valid latitude and longitude are required for the solar calculation.
Export is disabled	Capture at least one sample row first.

Open Device Sensor Recorder

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