The Finnish nautical chart in Lokimaps is not approved for navigation and does not replace an official, corrected nautical chart or required navigation equipment. Do not use it as the sole source for a voyage, water depth, clearance, or hazard decision.
Lokimaps displays Traficom's open chart-image WMTS, a viewing interface based on hydrographic data in raster format. Traficom lists that interface under open data, separately from official paper charts and ENCs for navigation and from quality-assured chart datasets, on its distribution page.
For the drawn marks, use Traficom's official explanation of symbols on Finnish nautical charts. Traficom states that its printed charts use international INT symbology based on the International Hydrographic Organization's S-4 standard. Use Traficom's own key for the Finnish symbols and abbreviations visible in the raster map.
Depths, depth contours, and colour areasDepths, depth contours, and colour areas
Soundings are individual depth values. Depth contours mark boundaries between depth ranges, and colour bands help separate shallow water from deeper water. Read a sounding together with its contour, surrounding tint, units, and chart datum. A blank space is not proof of deep or fully surveyed water.
Charted depth is not the same as the water available at this moment. Wind, atmospheric pressure, currents, regulation, and seasonal conditions can raise or lower the actual water level. Never add or subtract from a charted value until you have confirmed the chart's vertical reference and the current water level.
At the closest app zoom levels, Lokimaps enlarges the last available raster tile. Larger figures are not more precise, and enlargement cannot reveal omitted hazards. The tile view also does not provide the complete title block, edition, scale, caution notes, or correction status that you must check on an approved chart.
Rocks, foul areas, wrecks, and obstructionsRocks, foul areas, wrecks, and obstructions
The official legend distinguishes rocks by whether they are above water, awash, or below the chart datum, along with wrecks and other obstructions. Their symbols may be combined with depth values or danger lines.
Pay special attention to a foul area. Traficom explains that its black dotted danger curve encloses a widespread rocky or obstructed area where not every danger is charted individually. A symbol inside the curve identifies the kind of danger. Do not plan a route between the few visible rock symbols inside such an area, because the apparent gaps are not surveyed safe passages.
Fairways, routes, and restricted areasFairways, routes, and restricted areas
Finnish charts use different marks for fairway areas, channel centre lines, recommended tracks, leading lines, direction of traffic, anchorage information, and limits or restricted areas. Similar-looking dashed or dotted lines can carry very different meanings.
Do not confuse fairway class, safe clearance depth, and design draught. On N2000 charts, merchant fairways in classes 1 and 2 show the safe clearance depth using the minimum-depth symbol; the value is a secured fairway depth, not necessarily the area's actual minimum water depth. Their design draught is published separately. A channel draught printed on an older mean-sea-level chart is treated as a design draught. Traficom's channel-depth guidance explains the distinction. Neither the safe clearance depth nor the design draught guarantees safe passage, and each must be adjusted for the current water level. Shoaling, temporary work, buoy changes, traffic arrangements, and restrictions can also change. Consult a current official chart, fairway information, and Notices to Mariners before relying on a route.
Buoys, beacons, lights, and leading marksBuoys, beacons, lights, and leading marks
The symbol for an aid to navigation combines several pieces of information. Shape, colour, topmark, light colour, and light characteristic can each matter. Cardinal, lateral, isolated-danger, safe-water, and special marks must be distinguished using the official symbol key, not guessed from a small screen icon.
Lights and sectors may be accompanied by abbreviations for colour, rhythm, period, height, and nominal range. Leading lights or daymarks work as a pair only when observed and interpreted correctly. Zoom in enough to read every annotation, then confirm it against the current official material.
Cables, bridges, pipelines, and other clearancesCables, bridges, pipelines, and other clearances
Charts mark submarine cables and pipelines, overhead cables, bridges, ferry cables, fish farms, harbour works, and other objects that can affect a route. Clearance values refer to a stated vertical datum and may not equal the space available under current water conditions.
An anchor symbol or apparently open water does not override cable, pipeline, protection, or prohibited-area markings. Read the surrounding lines and abbreviations before anchoring or entering a constrained area.
Coordinate and height reference systemsCoordinate and height reference systems
Current Finnish nautical charts use EUREF-FIN, which Traficom says aligns with GPS's WGS 84 closely enough for practical navigation. A few green inland-water charts produced before 2003 use the older KKJ coordinate system and must not be treated as WGS 84 charts. Coordinate compatibility does not make every feature accurate to a metre, nor does it compensate for source-data age or chart generalization.
Finland is moving nautical charts to the N2000 height system, expressed as Baltic Sea Chart Datum 2000 (BSCD2000). In sea areas, depths and vertical clearances use the same reference level, either N2000 zero or, during the transition, annual theoretical mean water. Inland charts use different levels: a lake-specific low-water reference for depths and a high-water reference for vertical clearances. The actual water can fall below the depth reference or rise above the clearance reference. Traficom's general chart information explains these systems and links current sea and inland water-level services. Check the title and metadata of the approved chart you are actually using.
Before going on the waterBefore going on the water
Use this Lokimaps layer for geographic context and trip discussion, then prepare with authoritative navigation material:
- Obtain an approved chart at a suitable scale.
- Read Traficom's full Finnish chart symbol key.
- Confirm the depth and clearance reference system.
- Check current water levels, weather, and local warnings.
- Apply chart corrections and review Traficom's Notices to Mariners.
- Use suitable navigation equipment and keep a safe margin for uncertainty.
If a symbol, abbreviation, or line is unclear, treat the meaning as unknown until it has been checked in the official publication.