Sources, checks & limitations.
GrandTotality helps you compare possible observing locations for the total solar eclipse on 2 August 2027. It combines calculated astronomy with geographic context and practical travel links.
A planning beta, with visible uncertainty
The location audit, last updated 2026-09-30, covers all 1,450 catalogue records: coordinate validity, geographic country matching, eclipse calculations and the existence of referenced photo files. Individual source-check dates are recorded on each location card. These checks are not site visits.
- 845 pins agree with a reviewed coordinate source within the comparison tolerance.
- 60 have differing references and need the exact site confirmed.
- 502 need a separate coordinate reference checked.
- 43 excursion pin represents an approximate area.
“Source compared” means agreement within 750 metres, or 1 km for settlement centres. It does not certify an entrance or viewing spot. Some sources describe whole towns, archaeological areas or mountain ranges. Reference differences are retained for review instead of silently moving a pin to another source’s centre point.
Location cards show the review state, source and audit date. Read the complete record-by-record audit (JSON). Report a correction by email; your email app opens a draft for you to review and send.
The image review on 2026-09-30 checked the 1149 published photographs against source captions, reuse licences, attribution and file integrity. We removed 14 misleading or insufficiently specific photo associations from the earlier catalogue. Images cover 1450 records: 1236 have site photographs and 214 use clearly labelled stock illustrations. Stock captions identify the photographed subject and do not claim to show the named site. Where available, the photo year appears beside its credit. This is a visual/source consistency review, not independent verification of every photographed site. Read the image review (JSON).
Airfields are separate from scheduled passenger airports. Their presence does not confirm landing permission or tourist access. Accommodation and activity pins identify places or explicitly described meeting areas; confirm opening dates, availability and access with the operator. Activities on boats or away from a base need their own viewing-location calculation.
Eclipse calculations
Local circumstances are calculated using the Besselian fundamental-plane method, with Fred Espenak’s published NASA GSFC elements, WGS84 observer coordinates and elevation. The adopted ΔT is 71.7 seconds. Calculations use a smooth lunar limb and exclude atmospheric refraction and lunar mountains. These choices can shift contact predictions, especially close to a path edge.
Automated tests check the solver against NASA’s published centreline times, durations and solar angles across the path. The shaded map and distance estimates use NASA’s sampled path table. Use the calculated result at your exact coordinates when checking whether a place receives totality. Local timezone lookup is geographic and approximate near borders; future civil-time rules can change.
Weather history
NASA POWER provides CERES SYN1deg cloud data and MERRA-2 meteorology. Statistics cover 26 July to 9 August for 2016–2025, up to 150 daily observations. A “mostly clear day” has daily mean cloud at or below 20%; a wet day has at least 1 mm of precipitation. Missing values are excluded, and insufficient samples produce an unavailable state.
Cloud data represents an approximately 1° regional grid. Meteorology is approximately 0.5° × 0.625°. These are daily satellite/reanalysis statistics, not an eclipse-hour forecast or a promise of clear skies.
Terrain and maps
The optional terrain check samples Mapzen Terrain Tiles on AWS along the solar azimuth, every 100 m to 20 km. It includes geometric curvature and standing eye height, but not buildings, vegetation, atmospheric refraction or small terrain features missed by the grid. Terrain source credits.
Base maps credit OpenStreetMap contributors (ODbL). The regional illustration uses public-domain Natural Earth geography. Map tiles are not prefetched for offline use.
Map search
Worldwide place and address search uses Photon and OpenStreetMap contributors (ODbL). Coverage and availability vary; a search result does not confirm access or suitability for observing.
Places and airports
The catalogue reuses referenced geographic facts from the existing project, including Wikidata (CC0) and linked location references. Settlement data credits GeoNames (CC BY); mapped property references credit OpenStreetMap contributors (ODbL). Site summaries are original. OurAirports public-domain data supplies airport and airfield coordinates and classifications. Airport classifications and operating routes should be checked before booking. The site does not rank places by unmeasured popularity or guarantee access.
Current travel advice
Country links open the live UK FCDO advice. The coloured overlay and country summaries use a downloaded snapshot of FCDO alerts; the source check date appears in location cards. Detailed regional and border shapes are approximate and may be older than the country snapshot. Neither a colour nor the absence of a warning establishes that a location is safe. Read the live official regional restrictions and entry requirements before committing to a journey.