The author of this book Capt. Sanjiv Verma had personal experience when his vessels Magnetic compass had a large error and he successfully followed the suggestion herein to minimise the compass error to approved levels.
The download of the app doesn't contain viruses or any kind of malware. Bhandarkar Publications is the developer of Compass Calibration that can be found in the Educational category. Over 50 users downloaded and set up the tool and the latest release was on Oct 4, 2020.
Google Play shows that this application is rated 4.3 by its users. Download the free installer of Compass Calibration 1.03 and take a look at users' reviews on Droid Informer. The app runs on Android devices 3.0 and above.