Reading time.
Understanding the sources.

01 · The area and the objects

The wider centre of Sion, including the old town and the hills of Valère and Tourbillon, is covered by a 4.18 km² rectangle in Swiss LV95 coordinates: East 2,593,000–2,595,200, North 1,119,400–1,121,300. A whole object is kept when the centroid of its footprint lies in this rectangle. This is neither the whole municipality of Sion nor an administrative boundary. The first prototype covered 1.33 km² and 455 objects; this version extends the real data without inventing volumes between sources. The terrain extends 48 m beyond the edges.

The map shows 1,213 3D objects. One swisstopo object can combine several buildings or register addresses: “3D object” and “RegBL building” are therefore not synonyms. Five objects, uniquely associated with a non-existing status in the RegBL, were excluded from the 1,218 initial objects. The current existence of unmatched objects is not verified. The completeness check finds zero selected object lost in export, zero missing footprint and no missing tile in the area. The 1,218 selected objects split into 1,213 displayed and five explicit exclusions. Coverage audit.

02 · Three founding sources, three timeframes

Roofs, façades and footprints — ©swisstopo

swissBUILDINGS3D 3.0 Beta, FileGDB production files, tiles 2020_1306-12 and 2020_1306-21. The metadata were published in 2024 and updated in 2025. Of the displayed objects, 1,135 carry a 2016 survey vintage, 45 a 2020 one, 31 a 2013 one and two a 2014 one.

The fields HERKUNFT_JAHR, ERSTELLUNG_JAHR and REVISION_JAHR are never used as construction dates. EGIDs are empty in all local objects inspected. No national identifier was therefore assumed to be available.

Terrain — ©swisstopo

swissALTI3D, twelve 2024 tiles covering the squares East 2592–2595 and North 1119–1121. The 2 m GeoTIFFs are sampled on a 6 m display mesh of 383 × 333 points. Mesh elevations: 479.66 to 778.87 m. No vertical exaggeration. The 10 m contours are a graphic effect computed on this terrain; the base closes the terrain section.

Declared dates — Federal Statistical Office

Federal Register of Buildings and Dwellings (RegBL), level A public data, MADD production service eCH-0206, extract of 13 October 2026. Last update indicated: 01:03:08. The fields used are the EGID, the building coordinates, the status, the year GBAUJ, the period GBAUP and the number of floors GASTW. The dates remain administrative declarations, not archaeological datings. A year may correspond to a reconstruction or a conventional entry.

Dwelling data from the raw export are not included in the site. File URLs, their SHA-256 fingerprints and the hash of the RegBL extract are listed in the provenance manifest.

03 · How a date joins a volume

1. Read the Building_solid and Floor layers of the production tiles. Merge floor surfaces to obtain the footprints.
2. Look for the RegBL reference points contained in each footprint. A point close to the boundary, less than 1 m away but outside the footprint, is only flagged.
3. Accept only a unique reciprocal match: a single point in the object, and that point in a single object. Multiple candidates remain viewable but none of their dates is assigned to the volume.
4. Keep as unknown a declared year later than the model’s survey vintage. Seven cases are concerned. A unique spatial match remains a geometric hypothesis, without manual cadastral validation.

No date is propagated from a neighbour. No round year is spread around, and no height is invented from the number of floors. The surface triangulation keeps the measured coordinates. Buildings and terrain share LV95 / LN02; the local metric frame is centred at [2,594,100, 1,120,300, 500]. The vertical extent in a record is the maximum minus the minimum elevation of the whole model, not a façade height.

04 · Measured coverage

Of the 710 unique matches, 48 have no usable date and seven show the temporal incompatibility described above. The register lists 1,936 existing buildings in the area: 464 with a year (24.0%), 1,786 with a year or period (92.3%). The unique matches therefore cover 36.7% of existing records. The extract widened to neighbouring points contains 2,423 records of all statuses.

The loss of coverage comes mainly from the difference between 3D objects and register units. Segmenting large complexes after checking, or geometry with native EGIDs for Valais, could improve this coverage. The audit report sets out the counts and the schemas actually read.

05 · Reading the time slider without false precision

• Declared year: the volume becomes visible in that year. This rule does not prove that its current appearance existed then.
• Period: the volume is hidden before its known lower bound, pale and hatched during the interval, then normally coloured after its upper bound.
• Before 1919: the lower bound is unknown. At a date before 1918, existence remains only possible. No medieval year is inferred.
• Unknown: grey is kept by default at all dates and counted separately. A checkbox hides it.

At 1600 this gives zero objects whose declared year or upper bound is earlier than the chosen date, 45 possible objects and 558 without a date. This result is not an estimate of the number of buildings in Sion in 1600. Valère keeps the register period “Before 1919”; no more precise historical chronology has been imported.

06 · Opening the historical inquiry

An archive can document a construction, a transformation, a use or a demolition: these events must be distinguished. The documentary module provides for this distinction but does not yet contain any event assigned to a building.

• INSA, Sion 1850–1920, Raemy-Berthod, 2003: bibliographic lead.
• Inventory of the Archives of the Town of Sion: lead for the 1872 cadastre and archive files.

These links are neither a plot-by-plot verification nor a licence to reproduce the media. No archive image, Sion1475/Chronoscope model or Sion4D model is copied. The Tourbillon marker designates the hill and its measured terrain; it does not represent a reconstruction of the castle.

07 · Reuse and credits

The geodata are attributed to ©swisstopo and reused under the swisstopo OGD terms. The level A public data of the RegBL — Federal Statistical Office may be reused without restriction with attribution, according to the official dissemination page, consulted on 13 October 2026. The code licence does not replace the terms of these data.

The rendering adapts the Three.js scene, controls, lighting and some palette choices of Amsterdam, building by building — Alex Barakov, © 2026, MIT, revision 69ddbcf11b2c96c0900bff61b8ba7a6dc83298f4. Licence and source were reviewed before reuse. Amsterdam’s mechanisms for estimating or correcting dates are not reused. Inspiration: Paris, building by building — Sasha Bogachev. Three.js r186 — Three.js Authors, MIT.

08 · ScanVan: a complementary survey

From “Sources & method” on the map, a separate view lets you explore 100,000 points of the ScanVan Project: Images and 3D cloud points survey, Albane Descombes (EPFL), published on 12 May 2021, CC BY 4.0. The project brings together EPFL and HES-SO Valais. This date is the dataset’s publication date, not a construction date. The sample covers a loop of streets of about 394 × 336 m; it does not complete all the town’s buildings.

All 913,966 points of the sparse EPSG:2056 file lie within our area. We keep 100,000 regularly spaced indices, keep the colours and only change the reference frame for rendering. No surface is reconstructed and no point is invented. The elevation is taken without correction; its alignment has not been validated by an independent survey. Holes and outliers remain possible. The swisstopo buildings and the RegBL time slider are hidden in this view to keep the sources distinct. Provenance and transformation.

09 · Limits and reproducibility

Geometry, terrain and register have different vintages. Recent buildings may be missing, and some terrain/façade joins may be imperfect. One volume may combine annexes whose date differs from that of the main building. The prototype therefore does not by itself allow conclusions about the state of a plot at a historical date.

The preparation scripts keep the fingerprints of the source files. The standalone rendering uses three draw calls and 466,404 triangles. Date checks and checks of navigation, search, records, filters and rendering are documented in Chrome, on desktop and in 390 × 844 touch emulation on a Mac. A local diagnostic of 89 rotating frames gives about 8.35 ms per frame (95th percentile: 10.30 ms) in a 1,440 × 800 frame on that Mac; three draw calls, 466,404 triangles. This warm local-load result measures neither network delivery, nor a physical phone, nor Safari iOS. The ScanVan view adds a cloud of 100,000 points and hides the volumes.

To examine the pipeline or discuss a documented correction, the repository johannroduit/sion-by-building is private and requires access from its owner. The manifest, the audit report and this method remain publicly available. Any future correction should keep the source, the type of event, the dated interval and the degree of uncertainty.

10 · The layers of the new atlas

The interface brings together four readings: History, City, Mobility and Today. The time slider keeps the periods and their uncertainties. Aerial views and maps are independent documents; their date stays fixed when you move the buildings’ time slider.

Maps and aerial views · ©swisstopo

Siegfried map, state requested from the WMS service for 1910; SWISSIMAGE 1946; current SWISSIMAGE mosaic downloaded on 13 October 2026. A current mosaic is not a 2026 image. Documents projected onto the 2024 terrain, without restoring the old topography. Current volumes are hidden by default on the two historical documents; they can still be compared.

Heritage and transport

16 points from the national inventory of cultural property (FOCP, layer ch.babs.kulturgueter) and 40 FOT stops (ch.bav.haltestellen-oev), extracted on 13 October 2026. A heritage point belongs to the current inventory and assigns no date to the building. Departures come from transport.opendata.ch. Scheduled times and announced forecasts are distinguished. The national feed does not publish vehicles’ GPS positions. In Live mode, the positions shown are estimates, described in section 19.

City and landscape · OpenStreetMap

3,051 street and path segments, 94 railway segments, 35 watercourse segments and 1,212 point trees, clipped to the atlas area. A segment is not a whole street. The contributed inventory is partial; the trees have no measured height here. Geometry © OpenStreetMap contributors, under ODbL 1.0. These contemporary layers are paused during historical reading.

Measurements and feeds on request

Source: MeteoSwiss, station Sion SIO, 10-minute measurements, file updated about every 20 minutes; CC BY 4.0. UTC timestamps converted to Swiss time. Flow and level of the Rhône at Sion, FOEN station 2011: this station lies south of the displayed area. The level is expressed in metres above sea level, not as water depth.

OpenSky Network provides the positions reported in a wider sector (46.20–46.27° N; 7.30–7.42° E). An empty result does not mean that no aircraft is flying. Positions that are too old are discarded. No interpolated trajectory and no barometric altitude shown as geometric altitude.

The feeds pass through Cloudflare functions with fixed destinations, with a 1 to 5 minute cache and a limited timeout. Failures are displayed; no old measurement is presented as current. The Refresh buttons re-read the sources through this cache. Official drought, forest-fire and flood alerts are read from the federal geoportal (section 20). The tourist events calendar remains a link to its publisher, without automated extraction.

Provenance, area, counts and fingerprints of the sources. No visitor account, personal geolocation, advertising or visitor profile. The aggregated counter described below records neither IP address nor cookie.

11 · Live mode and view counter

The “Live” button returns to the present, turns on the city layers and opens a time-stamped summary. Departures and OpenSky positions are re-read every minute; MeteoSwiss and FOEN measurements every five minutes. The data published by their sources may be older. Refreshing pauses when the tab is hidden and stops when a historical year or ScanVan is chosen. No bus GPS position is available: the trains and buses shown are estimates described in section 19. No aircraft trajectory is simulated. The terrain, volumes and lines remain the surveys documented above.

The counter near the credits counts visible openings of the map after the geometry has loaded, reloads included. It does not count unique visitors. The start date of counting is shown when hovering over the number. Views before it went live are not known and not estimated. Each load uses an ephemeral random identifier to avoid counting the same request twice; it is deleted after 24 hours. No persistent visitor identifier, IP address or cookie is recorded by this counter. Automated visits may be included and interrupted visits may be missing.

Update log.

12. Forecasts and regional earthquakes

MeteoSwiss local forecasts use the SIO point (point 49, type 1), west of the centre. Minimum, maximum and rain totals are forecast over the local day (parameters tre200pn, tre200px and rka150p0). The issue date stays visible. Forecasts are updated by the source every hour; the server keeps them for at most thirty minutes.

Earthquakes come from the SED / ETH FDSN catalogue, checked manually. The filter keeps only the “earthquake” type, the last seven days and events within 50 km of the centre of Sion. Verification can delay publication. They are not moved into the 3D area. The server re-reads the source every five minutes on request.

Forecast source: MeteoSwiss, local forecast data. The terms of each source remain applicable.

13 · Heights, floors and mobility

The Height colouring represents the vertical extent of the swisstopo volume, from its lowest to its highest point. On sloping ground it is not equivalent to a façade height. The Floors colouring only uses the number declared in the associated RegBL entry: 671 objects filled, 542 without a value. Register and geometry vintages differ; this is not a historical survey of floors. Time filters and their uncertainties stay active in each reading.

The DATEX II counters of the traffic data platform (VDP), FEDRO comprise 12 detectors at three stations within 10 km of Sion, identified in reference table version 25 downloaded on 13 October 2026 (UTC). The flow, given in vehicles per hour for the measured minute, is converted to vehicles per minute and grouped by station. Mean speed is weighted by the number of contributing measurements. Detectors with an error, a measurement older than five minutes or a period other than 60 seconds are discarded; a change of the reference version suspends reading until checked. A zero is a received measurement, never a substitute value. Partial coverage, best-availability data, without additional statistical validation. No raw document or vehicle position is redistributed. FEDRO terms: standard access limited to six months, to be renewed or stopped.

The GTFS-SA disruptions are operators’ messages. The text filter Sion / Sitten and the periods active or starting within the next three hours give partial coverage: line messages without a named place may be missing. Deleted or expired messages are excluded. A publication older than fifteen minutes is flagged as old; a feed older than six hours is refused. The absence of a message does not prove that all services are running normally.

The two authenticated sources use Cloudflare secrets kept on the server side only. A shared D1 lock and cache limit each feed to one read per minute for the whole site. A failure does not refresh the date of old data and does not expose the token. The public views show local summaries and links to the sources.

14 · Comparison, energy and new readings

Comparing documents

The SWISSIMAGE images of the two local tiles requested for 1980 both indicate a 1980 acquisition. The WMS request for 2000 returns two 1999 acquisitions: the site therefore presents them as 1999. The comparison opens a top view with an adjustable divider, without contemporary volumes. The documents rest on the 2024 terrain; they do not reconstruct the old topography. swisstopo Journey through time.

Photographs and landmarks

Four public Wikimedia Commons records: a view by Adolphe Braun around 1860–1875 (public domain, Getty collection), a photochrom around 1890–1900 (CC BY 2.0), a photograph by Leo Wehrli dated 21 April 1948 (ETH Library, CC BY-SA 4.0), and a façade photographed by André Corboz (date not given, CC BY-SA 4.0). Thumbnails are not retouched; authors, licences and original records stay visible. The digitisation date is never used as the date the photo was taken. No photo automatically assigns a date to a 3D object. The six tour landmarks come from the current national inventory; the historical links complement this inventory without changing RegBL dates.

Declared heating and solar potential

The public RegBL field energySourceHeating of the first heating device is used only on spatial matches that are already unique: 678 records attached, 637 of them classified as gas, heating oil, air/ground/water, wood, district heating, electricity or other. Missing, undetermined or no-energy values stay in a separate category. The heating revision date is kept in the record. No additional matching, measured consumption, efficiency or energy assessment is inferred. This colouring returns to the present; it does not claim to show the fuels used at a historical date. RegBL, public data.

The layer ch.bfe.solarenergie-eignung-daecher of the SFOE roof solar suitability provides suitability classes. A click queries the roof surfaces at the chosen point: area, annual irradiation, estimated annual electricity production, inclination and available dates. The model and geometry vintages may differ. The roof image is projected onto the 2024 terrain, without reconstructing the roof planes in 3D. Volumes are hidden by default for readability. These estimates prove neither the presence of panels nor actual production.

Charging and air quality

DIEMO / SFOE: public data from participating operators, filtered to the LV95 area. EVSEs are grouped by station and de-duplicated by identifier; several connectors do not become several charging points. Points explicitly named “demo” or “test” are discarded. A status is only used when the feed declares dynamic information; otherwise it stays unfilled. Restricted and paid access is flagged. The time the response was received does not replace an individual operator timestamp, which is absent from the feed used. Availability stays declared, with partial coverage. One-minute server cache and re-read every minute in live mode.

RESIVAL / Valais Environment Service: PM10 for Sion and Sion Airport / NABEL, in µg/m³, rolling daily mean. The measurement window and the provisional status are shown. This is neither an instantaneous measurement nor a street-by-street estimate. Other pollutants are not inferred from this feed. Missing value: not given, never zero. Ten-minute server cache; checked on request and every five minutes in live mode.

Population, light and sharing

STATPOP / FSO: permanent resident population of Sion, municipality 6266, on 31 December, years 2010–2025. Spatial reference of the table: 6 April 2025. The whole municipality extends beyond the 3D rectangle; no population is assigned to a building. The update metadata received through the API are inconsistent with the table’s years and are not used as an observation date.

Sunlight uses the astronomical position calculated by SunCalc 1.9.0, in Swiss time for the chosen date, at 46.233° N and 7.360° E. Shadows are a geometric simulation on the measured volumes and the 2024 terrain, without tree heights or clouds. They represent neither a historical nor a meteorological survey. The simulation stops in the historical, solar, comparison and ScanVan views. SunCalc BSD licence.

The Share button copies a link containing the year, colouring, filters, base map, layers and camera position; the comparison also keeps both documents and the divider position. No personal geolocation is requested. Provenance and fingerprints of the additions. Public access does not grant a general licence on all collections: each source and each image keeps its own terms.

15 · Animation, replay and people

A visual entry into time

The opening sequence lasts about 18 seconds, excluding loading. It presents the measured volumes following the chronological classification described in section 05. The animated arrivals are a presentation effect, not a reconstruction of construction work. Undated objects stay grey, without an invented year. The animation plays on each normal arrival on the map, can be skipped and stops on any interaction. It does not start for a shared link to a specific view or when reduced motion is requested. No visitor or session indicator is used for this animation.

The slider gives more room to recent years: 1200, 1800, 1918 and 2026 correspond respectively to 0%, 25%, 45% and 100% of its width. Arrow keys move one year; Page up / down ten years. The bars group the 1,213 current objects by declared period: 46 before 1919, 112 in 1919–1945, 141 in 1946–1960, 183 in 1961–1980, 106 in 1981–2000, 67 since 2001 and 558 unassignable. This chart is neither an annual histogram nor a historical count of the town. It opens with the Breakdown button, to keep a compact slider on the map. The coloured line of the slider marks the main periods on this scale; its colours do not measure the number of buildings.

Replaying real received responses

A server collector consults the seven local readings every minute: weather, the Rhône, departures from Sion station, FEDRO counts, GTFS-SA disruptions, charging and PM10. The first response per feed and per minute is kept with its real time of receipt, without later rewriting. The same responses may also be recorded when the site is consulted. Storage keeps at most 26 minutes, and the interface offers a continuous window over the last twenty minutes. This window starts with the first samples actually recorded and contains no reconstructed history.

For the chosen moment, only the last response received at or before that moment is consulted. A gap of more than 90 seconds is flagged for fast feeds; the threshold is six minutes for weather, the Rhône and PM10. A known failure stays a failure; an absence does not become zero. Fast playback goes through these samples without inventing intermediate values. Measurement, publication and receipt dates are distinct and a source may have published an older observation. Departures are the timetables and forecasts announced in that response, neither vehicle positions nor a record of departures actually made. Weather forecasts, earthquakes and aircraft are not mixed with the replayed samples. Storage contains no visitor data.

The automatic ambience uses the astronomical position of the sun at the centre of Sion, according to the selected time, to slightly tint the background and the volumes. It is turned off with the Neutral option. It is neither a brightness measurement, nor observed street lighting, nor a weather simulation. Controls keep their style and readability. Standard FEDRO access started on 13 October 2026 ends automatically on 13 April 2027, unless explicitly renewed.

Lives linked to Sion

Six chosen entries, with no claim to completeness: Matthäus Schiner, Ignace Venetz, Raphaël Ritz, Maurice Zermatten, Noémie Schmidt and Sophie Lamon. The entries refer to the Historical Dictionary of Switzerland, the official portrait by the Canton of Valais, Swiss Films, Olympedia and the International Fencing Federation. Each card states its link with Sion, its dates and its sources. Entries, authors and sources. References to the HDS keep their attribution and their CC BY-SA terms.

The map links only point to contemporary public landmarks, such as the cathedral and Valère. They indicate no private home or current position of the people, and change no building date. To suggest a source, a person or a documented correction: hello@conexkt.world.

16 · Discover Sion, six documented steps

The map tour passes Valère, Tourbillon, the cathedral, Saint-Théodule, Maison Supersaxo and the Majorie. It uses the points of the contemporary heritage inventory, with camera moves and free navigation between the six steps. It represents neither a walking route nor a historical reconstruction. Reduced-motion preferences remove the gradual camera moves.

The short texts are original summaries of Sion Tourisme, Valère, the “La balade découverte” map by Sion Tourisme, the history of Tourbillon (Patrick Elsig / Association Sedunum Nostrum), the Bourgeoisie de Sion, Maison Supersaxo and Sion Tourisme, the castles. References checked on 13 October 2026 and available at each step. The stories change no RegBL date or geometry. The end of the tour gives access to the compared documents, photographs and current readings.

Animation and photographs of places.

The silhouettes of Valère and Tourbillon shown while loading are an original illustration. The temporary displacement of objects during the animation is a presentation effect; it describes neither a real trajectory nor a historical construction. The measured positions and volumes are fully restored at the end and when interrupted.

The 558 undated objects arrive independently of the slider and stay identified as undated. The animation does not turn a RegBL period into a precise year.

Six Wikimedia Commons photographs are manually linked to places explicitly named in their descriptions. Only one direct association with a 3D object is published: the Basilica of Valère, already named in the model. The other photos accompany the heritage records and the tour. No matching by mere proximity is used.

Each image keeps its author, its source and its CC BY-SA 2.5, 3.0 or 4.0 licence. Thumbnails are provided by Wikimedia, without cropping or retouching. The date taken is distinct from a construction date and from the model’s vintage. That of the Maison Supersaxo photo is not given. See the photo manifest and its associations.

Inspirations: Paris by Alexander Bogachev, Amsterdam / LAYRS by Alex Barakov, Geneva3D by Arnaud Ricci. The MIT credit of the engine derived from Alex Barakov is kept.

The rhythm of the Play button.

The register gives a precise year for 106 objects and an interval for 549 others. A uniform reading from 1200 to today therefore left a long phase without new groups, then sped up the recent periods too much. The Play button now presents the objects by declared period: before 1919, 1919–1945, 1946–1960, 1961–1980, 1981–2000 and 2001–2026. The 558 undated objects get a separate seventh chapter.

The length of each chapter leaves time to see its objects. Their order of arrival, the drops, rotations, bounces and camera moves are presentation effects. The visual order within an interval is not a construction chronology. No new date, no extrapolation from neighbours and no lost building is added to this animation.

During Play, the interface shows the name of the period and the number of objects appearing. The slider is placed at the group’s declared upper bound, without simulating precise years for objects whose date remains an interval. Manual reading by year keeps its earlier rules. Data, vintages and geometry stay unchanged.

One continuous scene, historical sources to consult

The main atlas keeps the measured volumes, the swissALTI3D terrain and the Sion4D palette throughout. The opening and Play present the buildings by declared period. The year slider keeps its reading of the contemporary model’s dates.

The Volumen/VWTM models of 1640, 1780 and 1840 remain available as historical sources in a separate study view. Their alignment is estimated; their geometry, terrain and sometimes generated heights do not directly replace the atlas’s measured objects. Visual proximity alone cannot establish a building’s identity or construction date.

To enrich a specific record, a documented match will be needed between the historical object, a verified plot or archive reference and the contemporary object. The owner references in the files remain documentary leads, without any inferred construction date.

See the places today in Google Maps

The records of contemporary buildings offer external Street View and directions links. The centres of the measured ©swisstopo objects are converted from LV95 (EPSG:2056) to WGS84 with PROJ, then matched by UUID. These are not verified entrances; Street View coverage depends on Google. No map link is assigned to historical objects whose alignment remains estimated.

These buttons open Google Maps without a paid API, key, embedded Google content or a route origin passed by Sion4D. Coordinates and provenance.

18 · Sion in 1640, 1780 and 1840

Explore the three reconstructions →. Source: 3D plan of the town of Sion (Volumen/VWTM), models provided among the resources of the Valais-Wallis Time Machine hackathon of 21–22 October 2022, organised by Conexkt. Credit taken from the wording used by the VWTM team. The years designate reconstructed states, not RegBL construction dates.

The three models comprise 452, 465 and 720 meshes, including the terrain and objects other than houses. All faces are kept: 69,410, 1,940,626 and 2,031,489 triangles. The files are losslessly compressed and loaded on request. Heights (449, 462 and 715 objects) and roofs are explicitly marked “Random” in the source. These generated values stay flagged; they are not presented as surveys or historical truths. Owner references are transcriptions from the source, without independent documentary validation.

As the source reference frame is undocumented, we estimate for each period a rigid rotation and translation by comparison with the atlas’s swissALTI3D 2024 terrain, without scaling or deformation. Alternating 100 m blocks are reserved for checking. The vertical RMS error on these blocks is 1.47 m in 1640, 1.39 m in 1780 and 1.38 m in 1840; 95% of absolute differences are below 2.48 m. Local differences reach 17 m. This is a check of surface agreement, not an independent measurement of cadastral accuracy or a recovered official CRS.

The terrain selector compares the source terrain with the current terrain. Current buildings can be shown as a blue wireframe; no object identity between periods is inferred and no volume is moved individually to hide an offset. Overlays may produce intersections. The current atlas’s slider keeps its rules and does not reconstruct lost buildings.

The models are published with permission and credit to Volumen/VWTM. The code’s MIT licence does not cover these models; the files declare no open reuse licence. Attribution: Volumen/VWTM. Provenance and fingerprints · Transformations and check errors · Valais-Wallis Time Machine.

19 · Estimated vehicles, visible weather and languages

Trains and buses. In Live mode, the server reads four public departure boards from transport.opendata.ch every minute: Sion station (trains), Sion Gare Bus Sédunois, Sion poste/gare and Sion Planta (buses), starting twelve to twenty minutes before the current time. The same journey seen from several stops is merged. For each journey, the passing times at successive stops are taken as published, including the forecast when there is one. The browser places the vehicle between two stops in proportion to the elapsed time, with smoothed starting and braking, along the shortest path in the OpenStreetMap street network; trains follow the main line, with an acceleration of 0.55 m/s², a cruising speed of 80 km/h and a stop at the station. The board does not publish the arrival time at Sion: it is estimated 60 seconds before departure for long-distance trains and 40 seconds for regional trains. Eight cars are drawn for long-distance trains, four for regional trains: indicative length. No GPS position is available; the real gap can reach several hundred metres, especially when times are rounded to the minute. Lines that pass none of the four stops are not shown. Vehicles are hidden during the replay of the last twenty minutes.

Visible weather. Rain, snow, the slant caused by the wind and the darkening of the sky follow the latest complete row of the ten-minute file of station SIO (MeteoSwiss, CC BY 4.0): precipitation, temperature, mean wind and its direction, sunshine duration. Snow below 0.5 °C, mixed rain and snow up to 2 °C. It is an illustration applied to the whole map. When the MeteoSwiss radar is available, its intensity above the town replaces the airport measurement for rain and snow (section 20).

Languages. The map interface is offered in French, German and English from a reviewed phrase glossary. A phrase missing from the glossary stays in French; no text is machine-translated on the fly. Names of stops, streets, places and institutions stay as in the sources. This page and the log are offered in German and English; in case of discrepancy, the French version prevails.

20 · Water, A9 traffic, radar and alerts

Watercourses. Watercourses and water bodies come from the atlas’s OpenStreetMap extract. The Rhône surface is formed by its two banks (OSM relation 1691018, ways 358613399 and 364893275), retrieved on 14 October 2026 through the Overpass API, then clipped to the area. Sections tagged tunnel=culvert or covered, including part of the Sionne beneath the town, are drawn dashed: about 1.2 km according to OSM. This follows the contributed inventory and does not date the covering. In Live mode, dashes move in the flow direction recorded by OSM; their speed is illustrative and does not measure the current. Geometry and provenance.

Traffic on the A9. The flow and mean speed of the FEDRO counting station closest to Sion (section 13) generate cars on the two A9 carriageways inside the area. Arrivals follow a reproducible random draw at the measured flow, split equally between the two directions. No real vehicle is located, and the town’s streets, which have no public counts, receive no animated traffic. Part of this section runs through the Champsec gallery: cars there are drawn on the terrain.

Precipitation radar. Every five minutes, the server reads the latest RZC image (instantaneous rain rate, Swiss composite at 1 km) from the STAC collection ch.meteoschweiz.ogd-radar-precip, in ODIM HDF5 format, with the jsfive library. The grid and its LV95 georeferencing are checked before use. Only a 61 × 61 km window centred on Sion is sent; the maximum of the nine cells around the town drives the visible rain or snow. An image older than 45 minutes is refused. A radar estimate is not a ground measurement and can under- or overestimate rain in an Alpine valley. MeteoSwiss documentation.

Alerts. The bell gathers three sources: the FOEN warning maps for drought, forest-fire danger and floods, queried at the centre of Sion on the federal geoportal (15-minute cache); local GTFS-SA disruptions (section 13); earthquakes of magnitude 2 or more within 50 km over 48 hours (section 12). Levels and wording stay those of the publishers. MeteoSwiss weather warnings and an events calendar for Sion were not found as reusable open data; they remain links.

Heat islands. The town of Sion documents its climate adaptation in reports and brochures, but no heat-island map downloadable as geodata was found for Sion on 14 October 2026. No layer is therefore drawn; a map published by the town or the canton can be added with its source.

Places, names and references · OpenStreetMap

The OpenStreetMap extract dated 14 October 2026 adds 123 places and named buildings within the atlas area. Find them in the main search or under “City → Places and landmarks”. This community-maintained present-day catalogue is not a complete heritage inventory. Names come from OSM or linked Wikidata records; OSM addresses label records with generic names.

57 places are located within a measured 3D footprint. Points must lie within a single footprint, more than one metre from its edge. Polygons require a unique overlap of at least 75% in both directions, without another substantially overlapping object. A point locates a place inside a volume; it does not establish that the place names the entire building. No nearest-neighbour matching is used.

11 places have a photograph: the six previously verified images are reused, with five additional views from files identified by Wikidata. Authors, individual licences and Commons records are retained. Images of collection artefacts or workshops are excluded from building views. Six OSM dates are shown verbatim as documentary references: they may refer to construction, an institution or its opening. They do not change building-register dates, filters, animations, geometry or colours.

Geodata © OpenStreetMap contributors, ODbL 1.0; Wikidata links, CC0; photographs under their individual licences. Sources, extent, counts, rules and hashes. Records load after the first map render and photographs load on demand. Reading these cards does not require requests to OpenStreetMap or Wikidata.

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