How a map is made

Data

• Traficom's nautical chart database. Depth areas, depth contours and soundings for the coast and the charted lakes such as Saimaa and Päijänne. The soundings date from 2001 to 2025.
• The Finnish Environment Institute's lake depth data. Depth areas and contours for about 1,900 lakes. Its Ranta10 shorelines tell us which lake your place is on, and each lake's greatest depth comes from the Järvi-meriwiki lake register.
• National Land Survey of Finland. Lakes and rivers from the topographic database, place names from the Geographic Names Register, a laser-scanned elevation model at 2-metre resolution, and the colour aerial photo for the edition that shows it.
• The Finnish Heritage Agency's register of ancient monuments. The rock paintings, hill forts, wrecks and other sites the map shows or points to.

The shape of the lakebed

Depth areas tell us where the water is, say, between 3 and 6 metres deep. For every point we work out a depth from how far it lies from the shallower and the deeper boundary, and the deepest hollows follow the soundings. That gives the bottom a continuous shape, which we draw as layers. On the test map of Yövesi the calculated bottom differed from the soundings by about a metre at the median.

Land

The elevation model shows rock, eskers and the grooves left by the ice age. On the map without the aerial photo the land is drawn in pale paper tones, so the water stands out. On the map with it, the land is the aerial photo in full colour.

Text

The place names on the map come from the National Land Survey's Geographic Names Register. Open waters, bays, lakes and rivers are in italics, islands and villages in upright type, and cape and farm names appear only near the spot you mark. Where two names would overlap, the less important one is left out. Depth numbers come from Traficom's soundings. They cover all the water at least 13 millimetres apart, and none sits on the edge between two layers, so each one stands out from its background. They are only on charted water, such as the coast, Saimaa and Päijänne. The deepest point on the map gets a ring and its depth, and if it is the deepest point of the whole lake, the map says so. The map also shows rock paintings, hill forts, stone labyrinths, wrecks and other rare sites nearby, from the Finnish Heritage Agency's register of ancient monuments. When one lies up to 3 kilometres past the edge, an arrow at the edge gives its direction and distance. When you order, you choose whether the map has names, depth numbers, these sites and the dot. The title and subtitle go below the map if you write them, and everything is set in EB Garamond. The data sources are listed on your order page and saved inside the files.

Print

The print file is 300 dpi, and the darkest depths are adjusted for matte paper so they don't run together.

Not for navigation

The map is a print, not a chart. The lakebed is calculated, and some of the data is years old. Don't use it on the water.