13.1: C.1- Introduction

Maps are a very important source of information for coastal engineers. This is true for both maps of the land adjacent to the coast and charts of the seas and oceans. We expect that these maps will give accurate information about the topography of the area, but often additional information relating to land use, infrastructure, elevation, etc. is provided. For the coastal engineer, charts of the seas and oceans are of particular interest. Such charts have been produced for many centuries to provide information to seafarers. The production of these charts was originally in the hands of private enterprises that had an interest in the trade between Europe and the East Indies and West Indies. In the early days of this trade, the maps and charts represented a great commercial value and they were kept secret by institutes like VOC and the British East India Company. Later, from around the start of the \(19^{th}\) century, with the formal establishment of the colonies the role of the governments in various countries became more important. The task of making proper maps of the sailing routes and the ports was then transferred to the various navies. Up to today, in most countries the national navy has a hydrographic department that is responsible for providing up to date information for the ocean navigation. An important part of that information is contained in hydrographic charts that give an impression of the local situation, including topography, bottom material, depths, sea levels, currents etc.

Such hydrographic charts are indispensable to sailors, and the presence of updated charts is mandatory on board of each seagoing vessel. When people cannot easily see what is below the surface of the water, maps and charts provide the only way for navigators to find out where it is safe for the ship to go and where it would be unwise to venture. Hydrographic charts are also an important tool for the coastal engineer, because these charts give reliable information on the conditions of the coastal zone. For engineers, however, it is not only the latest charts that are of interest, but certainly also the older maps that can still be obtained from the archives of the various hydrographic institutes. A sequence of maps gives a good impression of the longterm morphological developments. Historic maps can be obtained from the relevant hydrographic services.

This section shows the general principles governing the handling of maps and, more specifically, hydrographic charts and indicates roughly what information can be obtained from them.