Data sources & methods
Where the maps, coordinate definitions and calculations come from.
Map backgrounds
The current topographic background is OpenTopoMap, with OpenStreetMap and SRTM data. The sea-route tool also uses an OpenSeaMap seamark overlay and offers Esri satellite imagery. Attribution is displayed on each map. Availability and detail vary by provider and area.
Calculations
Turf.js calculates geometric distances, areas, bearings, midpoints and destinations. Proj4js converts coordinates using the projection definitions configured in the tool. The map interface uses Leaflet. These computations do not validate property boundaries or whether a route can safely be travelled.
Authoritative checks
Consult Lantmäteriet for Swedish coordinate reference systems and official geodata. Use Sjöfartsverket's official chart products and current navigation information for actual boating. Source pages linked below may be in Swedish.