Online valuation has a well-known flaw: a single model, a single answer, no nuance. The partnership between LaMap — a Geneva specialist in property data — and Rousseau 5 rests on a different conviction: the algorithm covers the first mile, the expert covers the last. Here is how this chain works, what it is worth — and what it does not replace.
What LaMap calculates — and how
The LaMap valuation tool assesses a property using seventy criteria: around twenty specific to the property itself — living area, rooms, land — and around fifty linked to its location — transport, schools, shops, air quality, neighbourhood tranquillity. Its methodological distinctiveness: the final figure is the median of three separate models — one based on listings, another on historical transactions, the third on value as perceived by owners. Cross-referencing independent models and taking their median is a well-established statistical practice: it offsets the biases of each source. The result: an instant and credible valuation as a starting point — for a villa just as for a Geneva flat.
What no algorithm sees
Transparency is the condition for trust, so let us say it plainly: a statistical model — even a triple one — sees neither the exact view from the living room, nor the quality of a renovation behind an old construction year, nor the plot’s potential, nor the real condition of the condominium. In Geneva, where these factors create considerable differences between two properties that are “identical” on paper, an online valuation is a frame of reference — never a sale price. This is exactly the doctrine of our guide “who should value your property”: each valuation method has its use, and the algorithm’s role is to open the discussion, not conclude it.
The handover: the expert on site
This is where the partnership makes sense: after the online valuation, you can book a free on-site assessment with a local Rousseau 5 expert. It refines the algorithmic figure with what only a visit reveals — the precise location and its nuances, recent renovations, the potential for construction or extension, the state of the market at that moment — then compares it against a comparative analysis of similar properties for sale and recently sold in the area. The final deliverable is not a figure but a file: a reasoned valuation, together with the accompanying sales and presentation strategy. The full method is that of our professional valuation — and, if you prefer discretion, it begins with a confidential audit.
The third pillar: actual sales, in open access
Between the algorithm and the expert, there is a third source — and we have made it openly available: transactions actually recorded. Our transactions map shows them municipality by municipality, and “how much did your neighbour sell for” goes down to street level. Cross-reference all three — the LaMap figure, the signed sales on your street, the expert’s eye — and you get the most honest possible reading of your value. To understand the mechanics of the calculation itself — weighted m², SIA m³, yield value — our guide to calculating the price breaks it down step by step.
What the partnership really produces: the data you consult
One point deserves to be stated clearly, because it is not visible anywhere on our pages: the “third source” above is not independent of the other two. The transactions we publish in open access reach us via LaMap, which collects and structures the transfers announced by the Geneva land registry before feeding them into our data chain.
In other words, when you look at the sales map for your municipality or search for what has sold on your street, you are reading data of official origin, collected by LaMap and reworked by us. What we add to it is processing, not raw material:
- the address of the sold property, extracted from the text of the deed rather than guessed by geocoding — it now appears on nine out of ten published sales;
- the neighbourhood, which the registry never names: it publishes by municipality and cadastral section, so that Champel ends up under “Genève-Plainpalais” and Conches under “Chêne-Bougeries”. We restore their proper names using the property’s postcode;
- the sorting of what matters: only two types of property — house and flat —, sales kept separate from inheritances and divisions, and outliers discarded rather than displayed.
This transparency about origin is not a courtesy detail. When you are shown a figure, the first useful question is “where does it come from?”. Here the answer fits in one line: from the land registry, via LaMap, reprocessed by Rousseau 5 — and never from an average of listings. A listing is an asking price; a deed is a fact.
A final word on what does not appear there, and never will: no identities. The text of deeds names sellers and buyers; we neither keep nor publish these names. They do not pass through our chain.
This is also what distinguishes sourced data from a figure found online: it can be traced back to its origin, publication by publication. If a price surprises you on our pages, it corresponds to a real deed, on a real date, for a real plot — you can check it.
Who this chain is for
For owners wondering without an immediate project: the online valuation gives an order of magnitude with no commitment or visit required. For sellers preparing to bring a property to market: the full chain — algorithm, actual sales, expert — produces a price that can be defended line by line. And for owners curious about their assets, who want to track their value over time: start online, check the map, call the expert the day the project matures. At every stage, you know who calculates what — and why. Technical terms in the glossary.