How high is Cerro Domuyo? Nobody has measured it

The number that has no author

Every page about Cerro Domuyo gives an elevation. Most give 4,709 m. They give it to the metre, without a range, without a date, and without saying who measured it.

Nobody measured it. That is the finding, and it holds up under every check available from outside a field survey.

The Instituto Geográfico Nacional — the state body that fixes Argentina's official heights — publishes no elevation for Cerro Domuyo. Its national Alturas y Depresiones Máximas table lists fifteen peaks. The lowest entry sits at 6,380 m. Domuyo is about 1,700 m below that cutoff, so it never appears. The table is not wrong; it was simply never built to reach this mountain.

IGN is capable of the work and has done it recently. It published a modern re-measurement of Aconcagua at 6,960.8 m. That decimal is the signature of an actual survey. Nothing comparable exists for Domuyo.

Five figures, no method

What circulates instead is a set of numbers that disagree with each other by 15 metres.

Two of these come from the same national geological service. Four, arguably five, are in wide circulation. Not one is accompanied by a survey report, an epoch — the date the measurement refers to — or a method.

That last omission is the important one. An elevation without a method is not a measurement. It is a figure that has been inherited.

Continue reading The geothermal project at Domuyo — forty years of about to happen →

The tag that cites an encyclopedia

The inheritance is traceable in one place, and it is worth seeing.

OpenStreetMap carries a summit node for Domuyo, node/474973520, tagged natural=volcano. Its elevation tag reads ele=4709. Its source tag reads source=Wikipedia.

That is the whole chain. The most machine-readable elevation for this mountain — the one that flows into apps, route planners and derived datasets — is a citation of an encyclopedia article, not a reading off an instrument. Anything downstream that treats OSM as an independent check is checking the number against itself.

English Wikipedia then manages to disagree with itself inside a single article. The Domuyo infobox gives 4,702 m, the Global Volcanism Program figure. The body text argues that Monte San Valentín at 4,058 m stands "about 651 metres less than Domuyo". Do the arithmetic: 4,058 + 651 = 4,709. The prose is running on a different number from the infobox above it, and neither is flagged.

None of this is scandalous. It is what happens when a figure with no origin gets copied for a century.

What this site measured, and what that is worth

The map on this site does not take any published figure on trust, so the terrain was sampled directly.

A 15 × 15 grid at 0.0015° spacing — a box roughly 2.3 km across, centred on the OSM summit node — was queried against three global elevation models. The results:

• SRTM 30 m: maximum 4,685 m, at −36.63810, −70.43280. The OSM node position itself reads 4,683 m.
• ASTER 30 m: 4,690 m.
• Mapzen: 4,685 m.
• jtreks' own SRTM terrain tile, the one the Ascenso game renders, tops out at 4,695.2 m.

Four independent samples land between 4,683 and 4,695 m. Every published figure sits above that band.

This does not refute 4,709 m, and presenting it as a refutation would be wrong. Global 30-metre digital elevation models systematically under-read sharp summits, and they under-read them in one direction only.

The reason is structural. Each cell in a 30 m DEM reports a single value for a patch of ground roughly 30 m on a side. That value represents the terrain across the whole footprint. A summit is a sub-cell feature: the true high point is a few metres across, and the ground falls away from it on every side. The cell containing the summit therefore averages the peak together with the slope surrounding it, and returns something lower than the peak. The sharper the summit, the larger the deficit — tens of metres is normal. A DEM reading below a surveyed height at a peak is the expected result, not a contradiction.

So the sampling does not settle the elevation. It brackets it. The honest statement is a range: 4,683–4,709 m, with the upper figure unsurveyed. Anyone quoting either end to the metre is quoting a convention.

The position, unlike the height, is sound

The elevation is soft. The coordinate is not.

OSM's node/474973520 sits at −36.63660, −70.43127, within 2 metres of the local DEM maximum found by the grid sample. For a summit node placed by hand from imagery, that is as good as it gets. The mountain is where the map says it is, even where it is not the height the map says.

Two published errors are worth recording so nobody re-imports them.

A wrong coordinate. The Cultura de Montaña ficha gives the summit as 36°37′47″S, 70°25′51″W. That decodes to −36.62972, −70.43083. SRTM puts that point at 4,422 m — about 260 m below the summit and roughly 800 m north of it. It is on the mountain, but it is not the top. Do not use it.

A wrong department. Almost every source places Cerro Domuyo in Departamento Minas. Query IGN's own georeferencing service at the summit coordinate and it returns Departamento Chos Malal. El Playón, Los Tachos and El Humazo all return Minas, which is where the Minas attribution comes from — the trailhead and the geothermal fields really are in Minas. The protected area straddles the boundary, which matches the province's own description of it: "noreste del Departamento Minas y noroeste del Departamento Chos Malal". The summit is on the Chos Malal side of the line.

How a summit elevation is actually established

The modern method is not complicated, which makes the absence of it here more striking.

A survey team occupies the summit with a GNSS receiver and logs satellite observations for hours, not minutes. Post-processing those observations against reference stations of known position yields an ellipsoidal height — height above the smooth mathematical ellipsoid that GNSS uses as its reference surface. That is not the number anyone wants. Heights on maps are orthometric: height above mean sea level, which is a physical surface shaped by gravity, not a smooth ellipsoid. Converting between the two requires a geoid model — a published surface describing, at each point, how far mean sea level sits from the ellipsoid.

Three components, then: the occupation, the processing, and the geoid model. A published survey names all three, plus the epoch, because ground moves and reference frames get revised. That is why Aconcagua's official figure carries a decimal and Domuyo's does not.

IGN did this work on Aconcagua. It has not done it on Domuyo, and no other body has published a substitute.

Why 15 metres matters less than it looks — and what does

The spread is not consequential for the thing it is usually invoked for.

Domuyo's claim to be the highest summit in Argentine Patagonia — under the definitions of Patagonia that include it, which is its own argument — does not turn on 11 or 15 metres. The nearest rival, Monte San Valentín, is 4,058 m. Volcán Tromen is 3,978 m by Spanish Wikipedia, 4,114 m by Andeshandbook — and it has an unsettled figure of its own. No competing peak is within 590 m. Move Domuyo anywhere inside its uncertainty band and the ranking does not change.

What the spread reveals is something else, and it is not about Domuyo's height at all.

A summit of national significance — a mountain the province markets, the Army staffs a registry for, and SEGEMAR instruments as one of six monitored volcanoes in Argentina — has never been surveyed. The number on the signs, the permits, the operator pages and the maps has no measurement behind it. It has been copied forward for long enough that the copying now looks like corroboration: five sources agreeing to within 15 metres reads as consensus, when it is one unattributed figure and its drift.

This is not unusual. It is how most elevations below the headline peaks work anywhere in the world. Domuyo is just an unusually clean specimen, because the chain is short enough to follow end to end: an encyclopedia article, an OSM tag citing it, and a set of government pages that never agreed with each other in the first place.

The correct way to state the height of Cerro Domuyo is this. The provincial figure is 4,709 m. No IGN survey supports it. Thirty-metre DEMs return 4,683–4,695 m, and they are expected to read low at a summit. The true value is somewhere in that range, and until someone stands on top with a receiver for an afternoon, that is all anyone knows.

📚5 Sources▾

• IGN, Alturas y Depresiones Máximas — https://www.ign.gob.ar/NuestrasActividades/Geografia/DatosArgentina/MaximasAlturas
• CCAM (Centro Cultural Argentino de Montaña), ficha Volcán Domuyo — https://revistadigital.culturademontania.org.ar/articulo/646cc94cfc0d3efac6f6e74b
• Andeshandbook, Cerro Domuyo — https://www.andeshandbook.org/montanismo/cerro/191/domuyo
• IGN / datos.gob.ar georef service, query at the summit coordinate — https://apis.datos.gob.ar/georef/api/ubicacion?lat=-36.6366&lon=-70.43127
• Monte San Valentín, English Wikipedia — https://en.wikipedia.org/wiki/Monte_San_Valent%C3%ADn

Elevation sampling for this article used OpenTopoData against the SRTM 30 m, ASTER 30 m and Mapzen models. Summit and route geometry comes from OpenStreetMap node/474973520 and the ways listed in this site's Domuyo map data.