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Have you updated?
If you have my "GPS Anti Spoof" app installed on your Android smartphone or tablet, be sure to update it. You can easily tell if you haven't done so yet by launching the app. If it jumps to Settings and won't display the main data screen, then you need to update! Note that it is often easier to delete and re-install, especially on older devices (don't worry: you won't lose your purchase if you have paid for the Pro version). By the way, the Pro version includes the Sun, Moon, all navigational stars and planets and works at sea or off-network for months without data access. The free version includes the Sun and a a few stars and will work for about five days without network access. Normal use in both versions does not require network access at all, so you can use it with data turned off and especially when at sea.

What's it for?
The intended use is to detect GPS Spoofing at sea. Just take a quick sight of the Sun or a star and tap Pause in the app. The altitude as displayed is the expected sextant reading, all corrections for IE, dip, refraction, etc already included and also corrected for DOV (deflection of the vertical by local gravitational anomalies) which is ignored by nearly all other apps and other tools in celestial navigation.

The app is also extremely valuable as a "sight trainer" and sextant tester. When you're practicing sights (on the water or even in your backyard with an "artificial horizon"), you get instant feedback on your work. Immediately compare your reading on the arc to the app's display. If they match, you know you're doing well right away --no sight reduction required.

Free version: https://clockwk.com/apps/?x=1
Pro version: https://clockwk.com/apps/?x=2

Frank Reed
Clockwork Mapping / ReedNavigation.com
Conanicut Island USA

PS: Where's the iOS (iPhone/iPad) version? I got sick of dealing with the app review process last Spring, but I'm going to try again with a little subterfuge this month (April). So stay tuned.

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