Sources and method
Tonttikartta is a free service that brings open Finnish authority data on properties, land-use plans and protected areas together on one map and one page per property. This page says who provides the service and why, where the data comes from, how a property page is made, what it is not and how to report an error.
Who runs Tonttikartta, and why
Tonttikartta is provided and maintained by OPL Consulting Oy (Y-tunnus 3222631-1, the Finnish business ID). The company's website is oplconsulting.fi and the service's email address is info@tonttikartta.fi. The service's contact details and terms have their own pages.
Information about properties, land-use plans and protected areas is largely open in Finland, but it is published in the separate services of several authorities. Tonttikartta brings it together on one map so that someone buying, owning or building on a plot can see in one place what information exists, where it comes from and where the official record is checked.
The service is free to use. The site may show Google advertisements; they are labelled as advertisements and have no effect on the property facts, the map or the guides. Advertising and cookies are described on the privacy page.
Where the data comes from
Tonttikartta uses open datasets from authorities and other providers. Most are licensed CC BY 4.0; OpenStreetMap data is licensed ODbL. A property page's sources section and the map's “?” help name the provider, the dataset release and the licence.
- National Land Survey of Finland: the cadastral index map (parcel boundaries), the topographic database (basemap and place names), municipal division and elevation model.
- Ryhti: open address and building datasets, and the index map of valid plans supplied by municipalities.
- Finnish Environment Institute: protected areas and Natura 2000, flood-risk areas and environmental noise.
- Geological Survey of Finland: the soil map.
- Finnish Forest Centre: forest stands.
- Finnish Heritage Agency: archaeological sites and the built heritage environment.
- Statistics Finland: municipal language status, postal-code areas and the population grid for optional map layers.
- Municipalities: plan indexes and planning projects from their own open interfaces, for the municipalities included. Coverage varies, and the map's planning panel lists it.
- OpenStreetMap contributors: nearby points of interest.
Some information, such as the National Land Survey's Karttapaikka, aerial imagery or a municipality's own map service, opens directly from the provider's own service. Tonttikartta does not process it.
How a property page is made
Every property page is built by software from the same chain of datasets. No page is written by hand and its text is not guessed: the summary's sentences are composed from the data's values with fixed sentence patterns, and where there is no data the page says so instead of filling the gap by inference.
- Property and parcels: the property identifier and parcel boundaries come from the National Land Survey's cadastral index map. One property can have several parcels (guide).
- Addresses: an address is attached to a property when the address point lies inside a parcel.
- Buildings: buildings in Ryhti's building dataset are matched to the property by location.
- Area: Tonttikartta calculates the area shown on the map from the parcels' map boundaries. It is not the official area in the cadastre (guide).
- Plans and protected areas: the property's map boundaries are compared with the plan data and protected areas. The result says what the data contains at the property. It does not settle building rights or whether a permit will be granted (guide).
- Surroundings: distances to nearby properties and places are straight-line distances between location points.
Tonttikartta does not add its own observations to the data, does not interpret boundaries and does not estimate a property's value. The same data is offered to AI assistants through the API, the MCP server and llms.txt, with the same sources and caveats.
What Tonttikartta is not
- Tonttikartta is not an official register, a register extract, a title certificate or a cadastral survey.
- Map boundaries are not boundaries established on the ground, and the area calculated from the map is not the area entered in the register.
- A plan feature in the data does not state building rights or whether a permit is needed. Those come from the plan documents and the municipality's building control.
- An empty result does not prove that a restriction or feature is absent.
- Tonttikartta does not broker properties or estimate their value.
Tonttikartta is an aid to exploration, not an official register, survey or authority decision. OPL Consulting Oy is not responsible for errors in the original public-source content and does not guarantee its accuracy, completeness or currency. Verify information with the original provider and the relevant authority before a purchase, construction project or other consequential decision.
For planning, building permits and restrictions, follow the document links where available and confirm the current situation with the municipality or responsible authority. General provider pages require a location or record search. Compare the source date, coverage and exact property—not just the map appearance.
How current the information is
Different datasets are published and imported on different schedules. The map is not a real-time copy of every source. Check any date shown with the information and consult the provider for its latest record.
A property page's sources section shows the page's update date and the release of each dataset used.
Errors, feedback and corrections
Email info@tonttikartta.fi with a map link or property identifier, the layer concerned, a description of the mismatch, and a verifiable source with its date. A screenshot helps. We can investigate and correct demonstrable errors in our processing or presentation. Corrections to the original source record belong to its provider; we cannot change an authority’s register.
When an error comes from Tonttikartta's own processing or presentation, we correct it. When it is in the source data, we say whose job the correction is: Tonttikartta cannot change an authority's register. General feedback and questions go to the same address; see contact.
Guides and their sources
The guides are written by hand. Every claim rests on a statute or authority page named in the guide's source list, and the end of each guide shows when the text was last checked. The guides do not state prices or coverage figures that go out of date.
Independence
Property facts, the map and the guides are not for sale: nobody can buy a place, emphasis or change in them. Advertisements are clearly labelled as advertisements. More questions and answers are on the FAQ page.
Checked against the sources in November 2026
Beta · This experimental service may contain errors or interruptions. Verify important details with the original provider.