Recreation of Forgotten Colombo Fortification Using GIS Techniques

Abstract

A map can be defined as a scaled graphic representation of the Earth’s surface. People have been using maps since the earliest civilizations. Initially, these historical maps were considered only as objects with historical value. However, with the development of Geographic Information System (GIS), new methods emerged to digitize these old paper maps using Georeferencing and overlaying them on various modern maps, such as satellite image platforms. Although the earliest map representation of Sri Lanka dates back to 139 AD, European colonials compiled detailed maps of the island. Under Dutch rule along the coastal areas of Sri Lanka, many maps of their fortifications were produced, with one of the most significant being the Colombo fortification. Originally constructed by the Portuguese and later developed and reconstructed by the Dutch, this monument is not visible today except for a few remnants. The Dutch compiled numerous plans and maps of the Colombo fortification; some are available for download in the Dutch archive in the Netherlands. Against this backdrop, the objective of this research was to georeference one of these historical Dutch maps, overlay it on a present-day Google map, and compare the past and present landscapes of the Colombo Fort area. Following the Georeferencing process, the historical map achieved a remarkably accurate overlay on the satellite map, with a Root-mean-square (RMS) error of approximately 7 pixels. The output provides a clear understanding of the Dutch fortification's function during the 17th century and the locations of its components in the present space of Colombo. Importantly, it underscores that while the fortress may be invisible today, the spatial arrangement of the current Colombo Fort remains akin to its Dutch predecessor.