SECTION 1
This manual is concerned with cartography, the art and science of making maps and charts. Those who practice this profession will be referred to as cartographers even though their actual titles may vary from map draftsman to graphic artist or from fisheries officer to scientific assistant.
A cartographer is a specialist in graphic communications who uses mapping as the main tool. The fundamental function of mapping is to provide accurate, clear and unambiguous information about the occurrence of various phenomena on or near the surface of the earth. A well drawn map is far more than a reduction of the area being studied; it is a carefully designed instrument that records, analyzes and displays the inter-related factors of the area in their true relationships to each other. In order to pass on this complex mass of information the cartographer must make effective use of graphics to illustrate a wide variety of concepts and ideas. In addition to the map format, cartographic personnel spend a large portion of their time producing such related graphics as display material, report illustrations, presentation graphics, statistical and scientific illustration and hosts of charts, graphs and diagrams. Many of these items are frequently incorporated into maps or are substituted for them. For planning in general and resource management in particular, maps and other graphics have no equal.
Cartography exists as a field of applied graphics because words have proven to be inadequate when describing complex spatial relationships. It is vitally important that the map content be assembled in a logical and obvious manner so that the user can easily understand the information being shown. When producing maps or graphics that illustrate scientific studies a cartographer may require the advice of a scientific authority in the field to ensure the correct interpretation and portrayal of information. Relevant statistics or data alone will not necessarily supply the information required. In many decision-making processes the truly useful information is often that which is obtained from studying the overall relationship of all the data. Graphics and graphical techniques can present these relationships in a manner in which even casual observers can readily appreciate the implications.
Cartography can play a major role in socio-economic development, but the cartographer must first identify, compile and analyse the most up-to-date and accurate spatial information available. Also of importance is the selection of the most appropriate cartographic techniques to display this information, which may include both traditional presentations and those dictated by the increasing availability of relatively inexpensive computers. The essential point is to select the most appropriate methodology for each situation rather than applying a particular technique because of its familiarity. The design, equipment and techniques have to be tailored to the requirements of the specific product. There is no reason to produce an expensive multi-coloured map using the latest techniques and materials if the same subject matter can be effectively represented by a simple pen and ink drawing.
One of the intentions of this manual is to show a number of alternatives, both in design and in production techniques, so that the most appropriate can be selected for each given situation. It should be stressed that the most appropriate alternative is the simplest solution that will give the required detail, accuracy and clarity. The nature of the graphics should be governed primarily by the user's requirements.
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.
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 (refer to Section 5). 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:
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 (Figure 1.1 a).
These show the boundaries of land subdivision, often with bearings and measurements and are used to record property ownership (Figure 1.1 b).
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.
Figure 1.1 Examples of general purpose (reference) maps: (a) planimetric; (b) cadastral; (c) topographic; (d) bathymethic.
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 (Figure 1.1 c). Potential problems of this particular usage will be discussed in Section 7 of this manual.
These show water depths and underwater topography. Uniform depths at specific intervals are usually connected by solid lines called bottom contour lines (Figure 1.1 d).
This second broad category includes all the map variants designed to fulfill 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 “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 (refer to Section 9).
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.
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 (Figure 1.2 a).
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; Waterways 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.
These are designed for air navigation, therefore emphasis is given to features of the greatest aeronautical significance. Major efforts are made to locate prominent landmarks, including population centres, distinctive natural and cultural landmarks, railways and major roads. Topographic information is often shown by spot elevations, contours and layer tints, the latter practice becoming increasingly common so that relief information can be seen at a glance. Aeronautical information is generally displayed in bold size, magenta coloured symbols to give emphasis to this critical aspect of the chart. As with nautical charts, mapped aeronautical information requires frequent revisions, therefore the compilation date should be carefully noted (Figure 1.2 b).
These are usually published by national, provincial or regional authorities to facilitate transportation over relatively long distances. Road maps indicate direction, distance and the quality of highways. Some may give related transportation information such as railways and airports. The map information is highly selective and in some forms, the map itself becomes more schematic than planimetrically accurate (Figure 1.2 c).
The large market for map products generated by the increasing numbers of tourists and travellers has fostered competition amongst both private and governmental map producers. Many of the resulting products are modified topographic or planimetric maps. They show improved systems of road classification plus locations of hotels, hostels, camp sites, historic places, beaches, museums, mountain refuge huts, ski lifts, ferries, etc. Some maps use hill-shading and layer tinting to accent sites for climbing, camping, skiing, trekking and viewing. The maps of large towns may be schematic and resort to pictures and drawings of significant locations to aid the user (Figure 1.2 d).
Figure 1.2 Examples of special purpose (thematic) maps: (a) nautical; (b) aeronautical; (c) road; (d) tourist and recreational.
