NASA SVS and Ernie Wright
- The method is published. Wright, E. and Young, C. A. 2024, "A Raster-oriented Method for Creating Eclipse Maps", The Astronomical Journal 168:163, published 2024 September 19, DOI 10.3847/1538-3881/ad6b23, open access under CC BY 4.0 1.
- The core idea is to test every map pixel, at every time step, against a lunar limb profile built from the SLDEM2015 and LOLA LDEM elevation models, with the observer lifted to the SRTM terrain height above the WGS 84 ellipsoid via the EGM96 geoid 1.
- The datasets are ESRI shapefiles and KML in WGS 84 longitude and latitude: umbra polygons at 1 s and 10 s steps, path outlines, central line, duration contours at 30 s and obscuration contours at 1 per cent and 5 per cent 2.
- The constants stated by SVS are DE421, Earth radius 6378.137 km, WGS 84 flattening, Moon datum radius 1737.4 km, Sun radius 696,000 km (959.645 arcseconds at 1 au) and, for 2017, = 68.917 s 3.
- Limb and terrain are explicit sources of path differences. Espenak states that limb corrections shift limits by 1 to 3 km. Solar-radius and Earth-orientation differences also matter. Ephemeris effects require matched-epoch comparison 4 1.
What this topic covers
This topic covers a published raster eclipse-mapping method backed by released data. It takes the 2024 Astronomical Journal paper formula by formula, inventories every SVS eclipse page and the files it releases down to the shapefile schema a developer will load, and sets the SVS path against the NASA eclipse site, EclipseWise, Jubier's maps and the Besselian Elements map to say which constant explains each disagreement.
Notes in this topic:
- Wright and Young 2024, the raster method: the limb-profile construction, the limb test, the antialiasing threshold, the broken-annular criterion and the SPICE calls of Appendix A, with what the paper leaves out.
- SVS eclipse pages and datasets: every SVS eclipse product by ID, the constants each page states, and the parsed DBF schemas of the 2017 and 2024 shapefile archives.
- SVS versus Espenak, Jubier and Irwin: the four predictors' inputs side by side and the size of the limb, terrain, radius and differences.
What this topic changes for the pipeline
The raster approach replaces a contact-time post-processing correction with a per-pixel limb test. Released polygons and city times provide reference products, while observed contacts supply independent evidence. The 0.02-degree profile spacing corresponds to about 600 m along the lunar circumference. It is a sampling interval, rather than a terrestrial path-edge uncertainty 1 5 6.
The compared paper and SVS product pages do not provide a source release of the raster solver. Bibliography notes identify the archived copies used for the documented releases 1 2.
References
- 1peer-reviewed Wright, E. and Young, C. A. 2024, A Raster-oriented Method for Creating Eclipse Maps, AJ 168, 163 Original publisher PDF preserved in Wayback snapshot 2024-11-19. Sections 4-6 and Appendix A checked 2026-09-30. 0.02 degree bins imply about 600 m along the Moon, not Earth edge accuracy. Printed broken-annular criterion needs common angular normalisation. PDF SHA256 5c07500302a852e21439b0cfe8b4a94c423fd92ca3315918818009d4cbf26447. CC BY 4.0.
- 2primary NASA SVS 5073, The 2023 and 2024 Solar Eclipses: Map and Data (2023) The data page: Making the Map statement (SRTM, LRO, DE421), layer descriptions for both zips, KML zips, cities JSON schema. Read from Wayback capture 2024-04-28.
- 3primary NASA SVS 4515, 2017 Path of Totality (2016) First limb- and terrain-corrected product. Constants table with WGS84, EGM96, 1737.4 km, 696,000 km (959.645 arcsec), DE421, EOP kernel, Delta T 68.917 s. Read from Wayback capture 2026-08-28.
- 4primary Espenak, F., Path of Total Solar Eclipse of 2024 Apr 08, NASA Eclipse Web Site VSOP87/ELP2000-85, Delta T 70.6 s, the 1 to 3 km and 1 to 3 s limb caveat, central line table, greatest eclipse 18:17:18.3 UT. Read via fetch tool.
- 5primary NASA SVS, 2024eclipse_shapefiles.zip (78.6 MB) Downloaded from Wayback capture 2025-02-12 and parsed: umbra_hi 6741 records at 1 s 17:56:00 to 19:48:20 UTC with 12 attributes; umbra_lo 1181 at 10 s; center, duration, ppath, ppath01, upath_hi, upath_lo; all .prj GCS_WGS_1984.
- 6peer-reviewed Quaglia, Irwin, Emmanouilidis & Pessi (2021), Estimation of the Eclipse Solar Radius by Flash Spectrum Video Analysis, ApJS 256:36 Full PDF read (var/downloads/quaglia2021_flash_spectrum_ApJS.txt). Flash-spectrum video from a site a few hundred metres inside the 2017 southern limit near Vale, Oregon. S = 959.95 +/- 0.05 arcsec. Gives sensitivity of duration and limit distance to solar radius, and compares Irwin's model with Occult and Solar Eclipse Maestro.