A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2019 Jun 8, 18:22 -0700
Earlier today, I wrote:
"If you want really accurate altitudes to test against your sextant sights, go grab a copy of my "GPS Anti Spoof" app on the Android Store (and for iPhone users, maybe soon on the iOS App Store)."
By "soon", I didn't mean six hours later, but that's how it has turned out! The iOS version of my app GPS Anti Spooof Pro (Pro includes the Sun, Moon, all navigational planets and stars) is now available on the App Store for about twenty dollars (USD). There is no free version for iOS users. Sorry.
The app calculates a live sextant altitude, exactly as it should appear on the instrument, from the current GPS position. The app has two basic functions.
1: TRUST THE SKY: If you're a reasonably skilled celestial navigator, and your position is mission-critical, then the app is a sensitive, accurate test of the GPS position. If your position is being spoofed by criminals, pirates, military or government intelligence forces, you can detect that with an easy, quick sight of your favorite celestial body. An observed celestial altitude will not match the app's calculated altitude if you're being spoofed. You can detect GPS Spoofing at sea using this app.
2: TRUST THE GPS: Turn it around. If you're learning or improving your sextant skills in circumstances where your position is not yet mission-critical and you have a reasonable expectation that the GPS position is near-perfect as usual, then the app is a sight-trainer, an instant check on your instrument and your skill using it. Shoot the Sun and compare. No paperwork at all. When learning, this also cleanly separates the two sides of the process of learning celestial navigation. You can quickly ramp up your skills using a sextant with the instant feedback from this app. Save the math for another day. Make sense?
Of course, as many of you know, this app has been available for Android users for over a year. If you have an Android smartphone or tablet.
Clockwork Mapping / ReedNavigation.com
Conanicut Island USA