Methodology

Construction of the Continental Divide

The construction of the map of the European Continental Divide is a composite from multiple datasources. These sources are publicly available maps from local agencies responsible for cartography or water management. The detailed maps depict river basins, in many cases individual basins are depicted at a detailed topographical level. 

These maps are then stitched together using the open source GIS program QGIS. As far as possible, the most detailed granular maps are the basis. However, this granularity varies from agency to agency and in some cases no detailed water basin maps are publicly available. For these cases (such as in eastern Europe), a very low granularity map of the all the world water basins from the USGS is used.

The shapefile of the Continental Divide is also available for download on the downloads page.

Continental Divide Map Available Documentation

For traceability to the underlying source agency, the segments of the continental divide are arranged in individual features of the map. The features are separated whenever there is a change in the underlying data source or a different divide is depicted. Each feature has the following data documented. This can be seen by clicking on the segment of the online version of the map. The following fields are available:

• F_NAME: Unique identifier for the feature, following a naming convention. The first two characters signify the ocean on the left side of the divide, the second two characters signify the ocean on the right side of the divide. The last three characters are numeric, numbered from north to south along the divide.
• WS_NAME: Unique short name for the divide. The characters before and after the underscore are a two to three character short name for the ocean on the left and right side of the divide respectively. 
• EU_MAIN: Depicts whether the divide is part of the main Continental Divide in Europe with the values ‘Y’ – Yes and ‘X’ – No. The main Continental Divide is considered the divide separating the northern and southern river systems. North of the divide, all water flows into the greater Atlantic Ocean system (Atlantic, Baltic and Arctic Oceans). South of the divide, all water flows into the greater Mediterranean Sea system (Mediterranean, Adriatic, Black and Caspian Seas). 
• SEA_LEFT: The main oceanic body of water to the left of the divide, when moving from north to south.
• SEA_RIGHT: The main oceanic body of water to the right of the divide, when moving from north to south.
• COUNTRY: ISO 2 Character Country code for the agency responsible for providing the underlying dataset. In most cases, this is the country in which the feature lies, but may also cross a country border, as discussed above. In certain instances, no detailed drainage dataset was found and the gaps and extensions were filled with the high level USGS Hydrosheds dataset. In this case the Country is listed as ‘–‘.
• STATE: The state or province of the agency.
• AGENCY: The name of the responsible agency providing the dataset.
• DATASOURCE: The name of the datafile from which the feature was derived.
• SCALE: The topographical scale of the datafile from which the feature was derived. When blank, the scale is not obviously  documented. The scale of ’15s’ refers to the 15 arc second scale provided in the USGS Hydrosheds dataset.
• URL: The URL where the dataset was found for this project.
• SELECTION: The criteria used to select the detailed drainage basins in the underlying dataset.
• LENGTH_KM: The length in km of each feature.

Map Background Layers

For the online version of the map, three background layers are provided, which can be toggled on or off using the legend on the top right of the map.

• OpenStreetMap (OSM): This map is useful for place names, borders and streets, however has very limited geological features.
• OpenTopoMap: Shows topographical details including elevation contours and waterflow directions.
• Thunderforest Outdoor: This map is the most useful for hiking and following the continental divide. Hiking trails are explicitly marked and often named. Please note this layer is a hobby project and the number of tiles is limited. No downloads please.