Secret VOC atlas chart of the Sunda Strait between Sumatra and Java Islands. By the famous Van Keulen family who operated a chart-making and publishing firm in Amsterdam for nearly 200 years.

Shown on this unique map is the Sunda Strait between Java and Sumatra. This extremely rare navigational chart was printed in Amsterdam around the year 1719 for VOC (Dutch East India Company) ships that were traversing the waters of the narrow waters between the two large Indonesian islands. The map features depth soundings and ocean hazards to aid sailors in their journey. The shallow waters of the Straits made it dangerous for large ships to sail without navigational aids.

The Sunda Straits has been an important shipping route for centuries, especially during the period when the Dutch East India Company used it as the gateway to the Spice Islands of Indonesia (1602-1799). However, the strait's narrowness, shallowness, and lack of accurate charting make it unsuitable for many modern, large ships, most of which use the Strait of Malacca instead. 

The maps from this "Secret VOC Atlas" are never in the market, and many collectors have waited a lifetime to find these, they are beyond doubt the non plus ultra of printed maps of the East Indies and the Indian Ocean. For many regions in Asia and Africa, these printed maps are the best and the only accurate early maps.

Van Keulen’s Secret VOC Atlas. For two centuries, from 1602 to 1799, the Dutch East India Company (VOC: Vereenigde Geoctroieerde Oostindische Compagnie) ruled the waters of Asia and Africa. Accurate charting of these waters was essential for successful and safe navigation. The VOC had their own mapmaking office. During the first 150 years, only secret manuscript charts were used, to minimize the risk of leaking knowledge to competitors.

From 1753 onwards, a printed atlas was used, with printed charts to navigate the waters from South Africa to Japan. The atlas was produced by Johannes (II) van Keulen, official hydrographer to the VOC, and was officially known as Part VI of the Zee-Fakkel (Sea-Torch). The atlas is known as the secret atlas because it was not sold and only used by VOC ships. For these reasons it is extremely rare, and only a few examples have survived. In addition, the number of charts in the atlas is often limited because ships that did not sail to India/Ceylon or China/Formosa/Japan were given restricted versions of the atlas that did not contain the charts of these areas.

There was a variety of reasons to publish the charts in print:

- Printed maps were more accurate and less prone to errors than manuscript copies.

- Loose maps were impractical and sometimes lost despite the strict policies of use.

- Last but not least, printed maps were cheaper to (re-)produce than manuscript maps.