Data, images and their origins

Sources & licences

Celeris combines its own calculations and models with open catalogues, geodata and astronomical photographs. These are the sources and adaptation notes, including those for the model previews on this website.

3D landmarks and model previews

The 127 available models are simplified planning aids, not survey-grade reconstructions. Plans, documented dimensions and photographic comparisons establish the silhouette. Depending on the site, OpenStreetMap contributes outlines, position or orientation; official geodata from Germany, Austria, Switzerland and Luxembourg supplement dimensions and heights.

• OpenStreetMap: © OpenStreetMap contributors, ODbL 1.0. Outlines simplified and combined with heights and model parts.
• Rheinland-Pfalz: © GeoBasis-DE / LVermGeoRP 2026, dl-de/by-2-0, www.lvermgeo.rlp.de; Daten verändert. DOP20 orthophotos, the LoD2 building model and the DOM1/DGM1 of the 2023 laser scan. Pfalzgrafenstein was measured off them, without including aerial image pixels or elevation values in the models.
• Saxony: Quelle: GeoSN (2025), dl-de/by-2-0; Daten verändert. GeoSN: DOP20, the DGM1 and the DOM1 of 2024, the LoD2 building model and the heights answered by the height service. The Bastei rock heights, the Moritzburg levels and the whole Göltzschtalbrücke height profile were sampled and simplified.
• Nordrhein-Westfalen: Land NRW (2025), dl-de/by-2-0; Daten verändert. Geobasis NRW: the airborne laser scanning point cloud, the DOM1, the LoD2 building model and DOP10. The radii and levels of the Kaiser Wilhelm Monument above Porta Westfalica were measured out of the point cloud.
• Baden-Württemberg: Datenquelle: LGL, www.lgl-bw.de, dl-de/by-2-0 (Datenlizenz Deutschland – Namensnennung – Version 2.0); Daten verändert. LGL OpenGeoData: DOP20 orthophotos, the 25 cm terrain model DGM025, the DOM1 and nDOM1 surface models. The Lützelhardt crests and rock were measured off these models, without including image pixels or elevation values.
• Tirol: Datenquelle: Land Tirol - data.tirol.gv.at, CC BY 4.0; Daten verändert. Terms of use: the tiris ALS surface and terrain models at 0.5 m and the orthophoto at 0.1 m. The plan geometry and tower heights of Kufstein Fortress were read off them.
• Kärnten: Quelle: Land Kärnten – KAGIS, https://kagis.ktn.gv.at, CC-BY-4.0; Daten verändert. The ALS 2 surface and terrain rasters at 0.5 m and the 2025 orthophoto. The Heiligenblut parish church was measured off them.
• BEV and basemap.at: Datenquelle: BEV, data.bev.gv.at — the federal airborne laser scan, its surface and terrain model over the Salzburg sheet — and Datenquelle: basemap.at, basemap.at for the orthophoto, both CC BY 4.0; Daten verändert. Every level of Hohenwerfen Fortress is a reading out of the federal surface model.
• swisstopo: © swisstopo, under the terms for free geodata and geoservices: swissBUILDINGS3D 3.0, swissSURFACE3D, swissALTI3D and swissIMAGE. The Brusio spiral viaduct, Spiez Castle and the Munot were measured off them.
• Luxembourg: Administration du cadastre et de la topographie (ACT), CC0 1.0, published on data.public.lu: orthophotos from the geoportail.lu open-data services, the LiDAR 2019 point cloud, the LiDAR 2024 terrain and surface models, the 2023 3D building model and the building footprints. CC0 1.0 asks for nothing; the source is named all the same. Bourscheid, Esch-sur-Sûre, Vianden and Fort Thüngen were measured off these data.
• Copernicus WorldDEM-30: sampled heights connect foundations to the app’s terrain. The elevation notices apply here too.

Previews use Celeris’s native 3D picture view and its original JSON model parts together with the actual Copernicus-based terrain tiles. The app’s terrain occlusion hides buried foundations. Images are resized and compressed as WebP; no photo textures or research photographs are added. Elevated virtual viewpoints and consistent simulated daylight are presentation choices, not measured photography locations or a recorded time of day. The elevation notices below also apply to the terrain shown in these images.

Elevation data

Copernicus WorldDEM-30, COP-DEM_GLO-30-DGED/2024_1, under COP-DEM-GLO-30-F. Converted to five detail levels and compressed tiles; additional height samples anchor the models. Full description and licence.

Stars, places and time zones

• Star catalogue and download: HYG Database by Astronexus and OpenNGC by Mattia Verga, CC BY-SA 4.0. Filtered, merged, converted to JSON and compressed.
• Point-of-interest database and download: © OpenStreetMap contributors, ODbL 1.0. Photographically relevant places filtered, ranked and compressed into degree cells.
• Time-zone grid and download: timezone-boundary-builder by Evan Siroky, built from OpenStreetMap, ODbL 1.0. Boundaries rasterised and compressed.

The photographed Milky Way

Milky Way panorama: ESO/S. Brunier, original photograph, CC BY 4.0. Resized, recompressed, softly limited to the galactic band and projected onto the simulated celestial sphere. Brightness and occlusion follow time and terrain. ESO terms of use.

17 deep-sky photographs

App detail pages carry the original credits. Separate working copies for the sky are scaled, oriented, made transparent in the background and adjusted to the sky’s brightness. The sources publish these photographs under CC BY 4.0; individual credits remain applicable. ESA/Hubble terms of use.

Meteor showers

The thirteen annual showers Celeris knows come from the shower tables of the Global Meteor Network: activity spans, maxima as solar longitudes, radiants and their drift, velocities, population indices and zenithal hourly rates are taken from the measured activity fits and the operational shower table of its flux monitoring, together with the network’s measured radiants. The Global Meteor Network is a worldwide network of video meteor cameras run by the Western Meteor Physics Group at the University of Western Ontario. Its data are released under CC BY 4.0.

What Celeris adds is its own arithmetic: when a shower peaks in a given year, how high its radiant stands over the local horizon, and how many meteors an hour that is worth from where you stand, with the moon, the twilight and the light pollution of the place taken into account. Those figures are Celeris’s, not the network’s.

ISS orbital elements

Source: CelesTrak, using data supplied by the United States Space Force. The app reads the unchanged two-line element record for the ISS (NORAD 25544) and computes position, passes and transits locally. The elements are not part of the star catalogue and are not assigned a Creative Commons licence here. The provider’s usage policy applies.

Software and other images

The astronomy uses SwiftAA on Apple platforms and Astronomy Engine on Android. Libraries retain their own licence files; the geodata licences do not alter them.

The landscape photographs on this website are by Stefan Engel. App screenshots show the Celeris interface; maps, astronomical images and geodata retain their respective source notices. Naming a provider does not imply their endorsement of Celeris.

Reviewed: 15 September 2026. Data transfers and storage are described in the privacy policy.