Map Classification
There is no universally accepted classification of maps, map graphics and related products. The following categories are introduced to provide a framework for discussion and the beginning of a working language for practitioners. Broadly speaking, maps can be divided into two categories, the first being general purpose or reference maps, the second being special purpose or thematic maps.
General Purpose or Reference Maps
The objective of general purpose or reference maps is to portray the relationships of a selection of different geographical features in an accurate and representative manner. Such features as roads, railways, settlements, water courses, elevations, coastlines and boundaries are typically displayed. These maps are usually produced in a series of individual sheets and carefully constructed by photogrammetric methods. Great attention is paid to positional accuracy of features so that in some cases these maps have the validity of legal documents. They are the typical products of major national mapping agencies and may be considered the foundation on which other mapping and related studies are built.
General purpose maps are fundamental to organizing and planning national and regional development. They are considered a basic national resource and are a foundation for further development. The main types of general purpose maps are as follows:
Planimetric maps: These show the horizontal position of selected features without elevations or water depths. They are often used as base maps on which to compile data for the production of special purpose or thematic maps.
Cadastral maps: These show the boundaries of land subdivision, often with bearings and measurements and are used to record property ownership.
Topographic maps (Hypsometric maps): In addition to the planimetric details of cultural and physical features that have been selected, these maps portray the shape and elevation of the terrain. This is usually done by contours, form lines, shading, colour gradients or hachures. National series mapping is normally composed of topographic maps.
Topographic maps are widely used for a multitude of purposes including selection of industrial sites, planning highways or settlements, routing power and telephone or pipelines, selecting dam sites, military planning, hunting, fishing, hiking and camping. They are thus true general purpose vehicles and are considered to be fundamental to the economic and resource development of a region. In addition, topographic maps are frequently used as base maps for specific studies because they are often the only available accurate mapping of a region.
Bathymetric maps: These show water depths and underwater topography. Uniform depths at specific intervals are usually connected by solid lines called bottom contour lines.
Special Purpose or Thematic Maps
This second broad category includes all map variants designed to fulfil a specific purpose which can be clearly identified in advance. Special purpose mapping is the fastest growing segment of the cartographic field because of its relevance to developmental activities. It is the area where a broad knowledge of design, technology and, in particular, the intended map user and use are required.
Thematic maps are composed of two major elements: the background or base map and the specific information being presented. The base map is prepared by directly or indirectly using information taken from general purpose or reference mapping. Additional base information and thematic data is derived from field work, image analysis, scientific studies, published statistics, or existing maps. It is plotted onto the base map using appropriate cartographic techniques. Normally the creation of a thematic map involves a process of compilation which includes the collection and manipulation of data from a variety of sources to produce a new product.
Thematic maps are also called distribution maps. They are a kind of a “geographical essay”, emphasizing single or multiple themes such as geology, oceanography, climatology, vegetation, soils, crops or social and cultural aspects of the population. Cartographers use these maps extensively to show, for example, such details as harbour installations, pollution sources, climatic variation, and fish distribution and migration patterns. These distributions may be shown by many different methods.
Transportation mapping is the largest sub-group within the thematic category, including Nautical and Aeronautical Charts, Road Maps and Tourist and Recreational Maps. Most of these are specialized forms of topographic mapping and have been re-designed to suit a more specific purpose.
Nautical charts: These are published primarily for mariners although they serve a wider public in many related ways. These charts are designed to provide all available information for safe marine navigation including soundings and bathymetric contours, obstructions, hazards, prominent landmarks and navigational aids such as buoys and lighthouses. The accuracy of these charts is of major importance in coastal regions because of the potential for marine accidents. The charts are constantly updated to keep abreast of natural and man-made changes.
Variations of these charts include: Small Craft Charts - designed for recreational use of inshore and harbour waters; Harbour Charts - details of anchorage areas, harbours and smaller waterways; Waterway Charts - details of canals and navigable water systems; Coastal Charts - designed for inshore navigation; Sailing Charts - primarily used by navigators to fix positions as they approach the coast from the open sea.
Map Utilization
In most developing countries topographic mapping has preceded all other types and has formed a foundation for subsequent mapping programs. Usually geological surveys are built onto these topographic bases and become the planning vehicle for mineral resource development. This is followed by such important studies as road and railway development, improvement in regional agriculture, development of water supplies and hydro-electric power from dam construction, large-scale cultivation of new crops and other aspects of national planning required prior to undertaking major capital projects. Other major mapping projects built on a topographic base have included: tourism planning and development; census studies; forestry management; industrial plant location; land ownership; land usage; environmental hazards; ecological studies; transportation; archaeological and anthropological studies; investigation, control and use of water resources; cadastral surveys; urban studies; sea defences; soil surveys; economic assessments; health investigations; irrigation systems; land reclamation; mosquito control in marshes; airport siting; housing developments; vegetation classification, etc. There have also been many schemes implemented because of military and internal security considerations and significant boundary disputes.
To the obvious economic and security aspects listed above must be added a number of benefits which are difficult to quantify. These would include the significance of mapping in education and a variety of recreational activities.
A reading of the above list will show that many of the subject areas have a direct impact on the marine environment. In fact, the division of the natural world into terrestrial and marine aspects is an artificial one as each affects the other.
The economic welfare of a nation or region is directly dependent upon the resources available to it and on the ability of the people to use these resources to their benefit. Inadequate knowledge often results in resources being over-exploited or even destroyed before they are truly appreciated. These resources include all of the exploitable minerals, soils, vegetation, wildlife and water. To derive benefits from a resource, it must first be identified and then managed. The map is the most efficient method of displaying the necessary resource information.
Many developing nations begin by establishing a geodetic survey network to construct an effective topographic mapping series. Not only are these maps vital for recording and planning of any kind, but also they are an economic investment that produces a major, though highly diversified economic return. They create economic benefits by preventing a great deal of unnecessary measurement, by eliminating an enormous amount of expensive field work and by shortening the time required to assess a development proposal.
Once the basic frame of the survey control network for topographic and planimetric maps is in place, it can become the base on which special studies both on land and in the marine environment can be built. This is not to infer that mapping is impossible without a survey control network; in fact some simple mapping techniques use readily available sources of information. Once the overview or reconnaissance phase is over, however, accurate measurements tied to survey control networks are usually necessary if major development is to take place.
Despite the benefits of national standard mapping, the current coverage of world topographic mapping is far from complete. Only 42% of the countries of the world are mapped at a scale of 1:50,000, considered to be the most useful scale available. At present rates, initial coverage won't be complete until the year 2000. A recent study by the International Hydrographic Office found that only 40% of the marine area covered by the Exclusive Economic Zone (EEZ) of the 39 countries it surveyed was adequately charted.
Standardized mapping tends to have a long life. Topographic maps, for example, are typically in circulation for 15–20 years before they are updated. Many potential users and uses for such a product cannot be foreseen. Some hydrographic charts have been in continuous usage, throught regular updates, for 70–100 years and their economic, social and convenience benefits can hardly be overstated. Such maps will easily return their cost many times over during their useful life and some will make possible a return on investment and human benefit unmatched by virtually any other development expenditure.
Maps have a catalytic effect on development and prevent the main source of haphazard planning which is the lack of easily understood information. In relation to the development and exploitation of marine resources, a mapping program can address critical information needs concerning, for instance, fisheries, oceanography, geology, navigation, coastal development and local political realities. In addition, such important topics as education and training can be addressed.
