Voyage on the Map

This explanation of the voyage on the map gives information about:

  • The dots on the map
  • Text balloon showing date and location
  • The colors of the dots

A very special map of the Atlantic Ocean can be seen when the main page of the blog is loaded. This is a West-Indian sea-chart, which seamen could use to either travel from Europe to Asia, or to cross the Atlantic Ocean to America. This parchment specimen dates from the end of the 17th century, and can be found in the Norman B. Leventhal Center in the Boston Public Library, Massachusetts, USA. The 18th-century navigators made use of smaller maps which showed only parts of the seas and coasts.

The Dots on the Map

Knipsel totaalbeeld kaart met route

On the map, the route of The Unity is marked by little dots. The number in the dots marks the number of days the ship has been traveling. In zooming in or out on the map, these dots are split up or merged. The buttons to do so can be found in the upper left corner of the map webpage, but zooming is also possible by scrolling. The map can also be dragged in all directions.

Knipsel zoomknoppen

Below the zoom buttons is another button which leads to a contemporary OpenStreetMap of the same geographical area.

Text Balloon Showing Date and Location

After clicking on a dot without a number, a balloon with the date and location of the day in question is displayed. The report of the day is opened via the “Read more” button.

Knipsel ballon datum en locatie

It is possible to open the daily reports of any day and location via the dots.

The Colors of the Dots

The dots have different colors. Blue dots indicate sea navigation and brown dots coastal navigation. The first mate of The Unity, Daniël Pruijmelaar, used both methods for noting down the position of the ship in the logbook.

For sea navigation, the first mate notes down the latitude and longitude of the ship’s position. The original latitude and longitude degrees have been corrected manually for this blog, especially because of the Prime Meridian: nowadays this line runs through Greenwich, England, whereas at the time of our voyage, the Canary Islands were used as the zero-longitude. Anther important adjustment concerns the positions throughout the trans-Atlantic crossing: these were corrected by hand, partly using information from the logbook.

For coastal navigation the first mate notes down the visual land markers in the logbook. Using the information garnered from these descriptions, modern coordinates were found for the route.

Overall therefore, the map shows the general route of the ship but cannot give the exact positions, since navigation methods of the time were simply not accurate enough.


West-Indian map by Hendrick Doncker
Collection: Norman B. Leventhal Center in the Boston Public Library. Map Reproduction Courtesy of the Norman B. Leventhal Center at the Boston Public Library.