GuardTrailsA calculated itinerary is only as good as what it reads. Here is what our engine reads, where it comes from, what it is used for, and what it does not tell you. Most of these sources are open: their authors publish them so that others can use them, and we owe it to them to say so.
The map, the places and the roads
OpenStreetMap. The worldwide collaborative map database. We read places, trails, the road network and accommodation from it. It also provides the map shown on the site and the starting point of geocoding, which places each stage on the map. The data is © OpenStreetMap contributors and distributed under the ODbL licence.
Protomaps. The base map you see on each trip record. It is built from OpenStreetMap data, in PMTiles format, and stored in our own hosting space: it is not served by a third-party map service (the storage itself is with our cloud host).
Photon. The open geocoder, based on OpenStreetMap, that places each stage on the map from its name.
Overpass. The interface that lets us query OpenStreetMap by area and by type of object. We use it to find the places, trails and accommodation around a stage.
OSRM. The road routing engine, also based on OpenStreetMap. It gives the duration of a journey, one journey at a time.
What these sources do not tell you. OpenStreetMap is written by volunteers: coverage varies from one region to another, and a road is drawn there, not guaranteed open. Ferry timetables, opening dates of mountain roads and permit quotas have no worldwide source. We detect that the constraint exists, never whether it fits your dates, and the trip record says so when that is the case.
Climate and season
Open-Meteo (historical weather data: ERA5 reanalysis and ECMWF analyses). The service through which we read the climate of each stage, over a rolling five-year window. It serves historical weather data from the ERA5 reanalysis (Copernicus Climate Change Service) and from analyses of the European Centre for Medium-Range Weather Forecasts (ECMWF); it chooses the most suitable dataset itself, depending on the period. The climate is measured at each stage, not once for the whole trip. Usage notices: Weather data by Open-Meteo.com (open-meteo.com), data under the CC BY 4.0 licence; for the ERA5 part: Generated using Copernicus Climate Change Service information 2026.
What this source does not tell you. It is a climate, not a forecast: it says what is usual at that time of year, not the weather you will get during your week.
Travel conditions
Foreign, Commonwealth & Development Office (United Kingdom), travel advice. We read the advice level for each country from it. Contains public sector information licensed under the Open Government Licence v3.0. The advice of the French Ministry for Europe and Foreign Affairs may differ: check it before you leave.
Cost
Eurostat. Price levels for each European country (purchasing power parities) and, for fuel, the European Commission's Weekly Oil Bulletin.
World Bank. The International Comparison Program (ICP) for countries outside Europe, read in a way that stays comparable with Eurostat's levels.
What these sources do not tell you. These are price levels by country, not prices. They give a cost benchmark, not a quote: the price of a room on a given date remains the host's.
Photos and how well known a place is
Wikimedia Commons. The photos on the trip records come from Commons. Each photo carries its author and licence beneath it.
Wikipedia and Wikidata. We use them to estimate how well known a place is, that is, whether it is a must-see or a local curiosity.
What we build ourselves
The engine, its settings and its checks are our own: the heat ceiling, register saturation, the day with no plan, tolerance for changing base, stage or accommodation, rain hours. The thresholds are engine parameters, set for each traveller, not rules. We do not sell trips and take no commission on accommodation or flights.
An error, a missing source?
If a figure in a trip record looks wrong to you, or if an attribution is incomplete, write to us: corrections are published. The full notices are in the legal notice.
Corrections: what we withdrew, and when
Anything published here may be wrong. What is wrong gets corrected, dated, and left visible.
The rule
An error that is reported and verified leads to a correction in the text, with a dated note at the foot of the page. The old version is not erased: a site cannot be judged on pages that were silently rewritten.
We distinguish two things.
An error of fact — a wrong number, a wrong date, a misplaced location. Corrected as soon as verified.
A disagreement — you experienced differently what we describe. Published as is, not blended into the text. Two contradictory experiences are more informative than an average.
What we have already corrected
These corrections did not come from readers. They came from our own measurements, which invalidated what we had written.
26 September 2026 — northern rain risk was counted the wrong way. We stated that a Nordic coast saw rain almost one day in two, a figure taken from rainy-day statistics. Recounted in hours of rain during the active day, the risk turned out to be much lower: a forty-minute shower counts as a "rainy day" and spoils nothing. Direct consequence: the argument that an extra week can be bought as insurance against rain no longer held. It was withdrawn from the study It isn't the north you're looking for.
26 September 2026 — a ranking we had no right to make. We presented tropical altitude as the best climate profile among the four families that let you escape summer heat. We have never travelled in that family: the ranking rested on what logic promised, not on anything we had experienced, and measurement did not confirm it. The ranking was withdrawn. The four families answer the same question, and the choice depends on the traveller's ceiling.
September 2026 — the cost of a move was counted as a flat rate. A whole day counted per stage, whatever the distance — which favoured a country with three hours of driving a day and penalised one with a single hour. Replaced by a cost that grows with distance.
Report an error
Through the contact form, with the page concerned if possible, and what makes you think it is wrong. A contradictory measurement beats an impression, but an impression beats silence.