# GPS Anti Spoof Pro — sextant sight analyzer > Celestial navigation tool for altitude comparison and GPS spoofing detection. (iPhone/iPad app by Frank Reed.) - Source: https://appshunter.io/ios/app/gps-anti-spoof-pro/id1379926231 (this page in markdown: same URL + `.md`) - Developer: [Frank Reed](https://appshunter.io/developer/1379926230) - Category: Navigation, Education - Price: $19.99 - Rating: 5.00/5 from 7 App Store ratings · 2 written reviews indexed - Age rating: 4+ - Requires: iOS 11.0 · 12 MB - Languages: American English - Released: 2019-06-11 - Data updated: 2026-07-28 - Monetization: paid - User reviews in markdown: https://appshunter.io/ios/app/gps-anti-spoof-pro/id1379926231/reviews.md ## What is GPS Anti Spoof Pro? Instantly compare observed celestial navigation altitudes with high precision, live calculated altitudes. Shoot the Sun, tap pause in the app, and get instant feedback. Standard version includes data for the Sun, Venus, and two stars. The Pro version of the app is for serious navigation use and includes data for the Sun, Moon, Venus, Mars, Jupiter, Saturn, the 57 standard navigational stars, plus Polaris. Both versions function off-network and at sea however the standard version only works for ten days off-network. The Pro version can function for weeks in the middle of the ocean without network access. This app calculates the exact sextant altitude that should be observed in celestial navigation at sea or on land assuming that the GPS position is correct. No paperwork is required, no tables of corrections. All corrections are included automatically: index error, system time error, dip of the horizon, refraction, temperature and pressure corrections to refraction, altitude above sea level, parallax, and also gravitational deflection of the vertical (a correction of up 2 nautical miles not handled by any other celestial navigation sight-clearing product) are all included automatically. If the GPS position is wrong, due to Spoofing at sea, observations will not match. With this app and occasional quick sextant sights, mariners can reliably detect GPS spoofing. No GPS Spoofing? The app also functions as a celestial navigation trainer: take a sextant sight and immediately compare against the app's display. No paperwork and instant feedback will improve celestial sextant skills in hours instead of days or weeks.  The app works off-network, even in the middle of the ocean. If a network connection is available, the app will download temperature and pressure information automatically. Or weather data can be entered manually, if desired. The ephemeris data is generated from the same JPL numerical integrations of lunar and planetary motions used by the official Nautical Almanac and Astronomical Almanac. All coordinates are accurate to one second of arc, and displayed altitudes are accurate to a tenth of a minute of arc. ## Key features - Celestial altitude comparison - GPS spoofing detection - Celestial navigation trainer - Automatic correction calculations - Offline functionality - Sun, Moon, planet, and star data ## Recent user reviews (2 of 2) All indexed reviews: https://appshunter.io/ios/app/gps-anti-spoof-pro/id1379926231/reviews.md ### 5/5 — Delivers on claims! *2025-04-20* Frank is a genius for developing this app. I’m a novice so checking my sights against the app is a godsend! Also, doesn’t collect any data from my phone or the app. Appreciate the privacy. I do wish I could turn off all features which use internet connectivity when present. ### 5/5 — Works as Advertised!! *2024-09-20* This app is fantastic for checking your GPS. Excellent for educational purposes to check celestial sights. I highly recommend this app. ## Frequently asked questions about GPS Anti Spoof Pro ### What is GPS Anti Spoof Pro used for? GPS Anti Spoof Pro is used to compare observed celestial navigation altitudes with live calculated altitudes. It helps mariners detect GPS spoofing and also serves as a celestial navigation trainer. ### Does GPS Anti Spoof Pro work offline? Yes, GPS Anti Spoof Pro works off-network and can function for weeks without network access, making it ideal for use in the middle of the ocean. ### What celestial bodies can GPS Anti Spoof Pro track? The Pro version includes data for the Sun, Moon, Venus, Mars, Jupiter, Saturn, the 57 standard navigational stars, and Polaris. ### How accurate are the calculations in GPS Anti Spoof Pro? The ephemeris data is highly accurate, with coordinates precise to one second of arc and displayed altitudes accurate to a tenth of a minute of arc. ### Does GPS Anti Spoof Pro require paperwork? No, GPS Anti Spoof Pro eliminates the need for paperwork. All necessary corrections are included automatically, and feedback is instant. ### What is the price of GPS Anti Spoof Pro? GPS Anti Spoof Pro is a paid application priced at $19.99. ### How often is GPS Anti Spoof Pro updated? The latest version is 1.0.39, and the app was last updated on September 1, 2025. Updates ensure continued reliability and accuracy. ### What devices support GPS Anti Spoof Pro? GPS Anti Spoof Pro is supported on iPhone, iPad, and iPod devices. ## Version history (last 5 releases) ### 1.40 — 2026-06-04 maintenance update ### 1.0.39 — 2025-09-01 Maintenance update ### 1.0.38 — 2025-04-23 maintenance update ### 1.0.37 — 2024-11-27 maintenance update ### 1.0.36 — 2024-09-24 maintenance update ## Apps similar to GPS Anti Spoof Pro | App | Rating | Price | Category | | --- | --- | --- | --- | | [EZ Celestial Navigation](https://appshunter.io/ios/app/ez-celestial-navigation/id1547239240) | 4.9 (19) | $29.99 | Navigation | | [Pressure Altimeter Tracker](https://appshunter.io/ios/app/pressure-altimeter-tracker/id6449918068) | 5.0 (5) | Free | Navigation | | [Airborne Flight Instrument](https://appshunter.io/ios/app/airborne-flight-instrument/id1071898324) | — | $2.99 | Navigation | | [EZ Nautical Almanac](https://appshunter.io/ios/app/ez-nautical-almanac/id6468887411) | 5.0 (5) | $9.99 | Navigation | | [EZ Lunars](https://appshunter.io/ios/app/ez-lunars/id1607908384) | 5.0 (1) | $24.99 | Navigation | | [StarPilot](https://appshunter.io/ios/app/starpilot/id359071446) | 4.9 (7) | $49.99 | Navigation | ## More apps by Frank Reed - [GPS Anti Spoof](https://appshunter.io/ios/app/gps-anti-spoof/id1467017105) All apps by Frank Reed: https://appshunter.io/developer/1379926230 --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-07-28.*