# GPS Anti Spoof — sextant sight analyzer > Celestial navigation tool for altitude comparison, GPS spoofing detection, and training. (iPhone/iPad app by Frank Reed.) - Source: https://appshunter.io/ios/app/gps-anti-spoof/id1467017105 (this page in markdown: same URL + `.md`) - Developer: [Frank Reed](https://appshunter.io/developer/1379926230) - Category: Education, Navigation - Price: $3.99 - Rating: 5.00/5 from 3 App Store ratings - Age rating: 4+ - Requires: iOS 11.0 · 12 MB - Languages: American English - Released: 2019-06-16 - Data updated: 2026-08-31 - Monetization: paid - User reviews in markdown: https://appshunter.io/ios/app/gps-anti-spoof/id1467017105/reviews.md ## What is GPS Anti Spoof? 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 - Compare observed vs. calculated celestial altitudes - Detect GPS spoofing - Celestial navigation trainer - Offline functionality - Automatic correction calculations - Pro version with expanded celestial body data ## Frequently asked questions about GPS Anti Spoof ### What celestial bodies are included in GPS Anti Spoof? The standard version includes data for the Sun, Venus, and two stars. The Pro version expands this to include the Sun, Moon, Venus, Mars, Jupiter, Saturn, the 57 standard navigational stars, and Polaris. ### Can GPS Anti Spoof be used without an internet connection? Yes, the app functions off-network and at sea. The standard version works off-network for three days, while the Pro version can function for weeks without network access. ### How accurate are the calculations in GPS Anti Spoof? The ephemeris data is generated from JPL numerical integrations, ensuring accuracy to one second of arc for coordinates and a tenth of a minute of arc for displayed altitudes. ### Does GPS Anti Spoof have ads? No, GPS Anti Spoof does not contain advertisements. ### What is the price of GPS Anti Spoof? GPS Anti Spoof is available for a one-time purchase of $3.99. ### How does GPS Anti Spoof help with GPS spoofing detection? By calculating the exact altitude that should be observed based on celestial bodies and comparing it to your observed altitude, the app can highlight discrepancies if your GPS position is incorrect due to spoofing. ### What age rating does GPS Anti Spoof have? GPS Anti Spoof has an age rating of 4+, making it suitable for a wide range of users. ### How often is GPS Anti Spoof updated? The latest version, 1.0.39, was last updated on September 1, 2025, indicating regular maintenance and updates. ## Version history (last 5 releases) ### 1.40 — 2026-06-04 maintenance updates ### 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 | App | Rating | Price | Category | | --- | --- | --- | --- | | [Star Rover HD - Night Sky Map](https://appshunter.io/ios/app/star-rover-hd-night-sky-map/id437217048) | 4.7 (95) | $1.99 | Education | | [Art To Income](https://appshunter.io/ios/app/art-to-income/id6745507031) | 5.0 (1) | Free | Education | | [E6B Pro Pad](https://appshunter.io/ios/app/e6b-pro-pad/id586546393) | 4.7 (6) | $14.99 | Education | | [Star Pupil](https://appshunter.io/ios/app/star-pupil/id6463496579) | 5.0 (1) | Free | Education | | [Prime Factorization Factorizer](https://appshunter.io/ios/app/prime-factorization-factorizer/id829728229) | 5.0 (3) | $3.99 | Education | | [Most Common Chinese Words](https://appshunter.io/ios/app/most-common-chinese-words/id6462861429) | 1.5 (2) | Free | Education | ## More apps by Frank Reed - [GPS Anti Spoof Pro](https://appshunter.io/ios/app/gps-anti-spoof-pro/id1379926231) 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 2026-08-31.*