Altitude displays N/A in GPS Info panel when antenna height contains an invalid (NaN) value

Description

When the antenna height field contains a NaN (Not a Number / invalid non-numeric) value, the Altitude field in the GPS Info panel displays N/A instead of the actual GPS altitude. This affects both internal and external GPS connections and is reproducible on both iOS and Android.

Environment

[x] Staging

Application (+ app version, build, operating system)

Mergin Maps Mobile App

• iOS version: 2025.6.0 — iOS 26.0 / iOS: 26.6.921312
• Android version: 2025.6.0 — Samsung Galaxy A53 5G, Android 15

Steps to reproduce

1. Open the Mergin Maps mobile app.
2. Navigate to the GPS Info panel.
3. Set the antenna height field to an invalid or non-numeric value (NaN).
4. Observe the Altitude field in the GPS Info panel.
5. Repeat with both internal GPS and an external GPS receiver.

Actual results

The Altitude field in the GPS Info panel displays N/A when the antenna height contains an invalid (NaN) value. This occurs for both internal and external GPS connections.

Expected results

The Altitude field should display the actual GPS altitude regardless of the antenna height value. If the antenna height is invalid, the app should either:

• Fall back to displaying the raw GPS altitude without antenna height correction, or
• Display a clear warning that the antenna height value is invalid, while still showing the GPS altitude.

Screenshots or logs
(Please attach screenshots or relevant logs if available)

https://github.com/user-attachments/assets/ac255cc5-1bc8-4b1a-b24a-bbf2626e5c7a

Conclusion
Created by Claude and supervised by a human test analyst.

Start by locating the GPS Info panel and the code that combines antenna height with altitude, then reproduce the issue with an invalid antenna-height value for both internal and external GPS. Done means the panel still shows the raw GPS altitude or a clear invalid-height warning instead of N/A; verify the result on iOS and Android paths.