A. BLAIR RAINS *(*) A. Blair Rains: Principal Scientific Officer, Land Resources Division, Ministry of Overseas Development, Tolworth Tower, Surbiton, Surrey, England.
The choice of scale, symbols and colours is important in mapping vegetation. Too much information can detract from the usefulness and from the legibility of maps. The grouping of related units and the use of overlays are methods of improving the presentation of data.
Vegetation maps continue to appear in a variety of new formats; some of these formats are extremely ingenious in their portrayal of information, but this does not ensure that the map can be easily read.
We are primarily concerned with the mapping of floristic variations and sometimes with the density of the herbaceous cover within a small number of physiognomic units.
The inclusion of other environmental features such as land systems, soils, climatic data, or land use on the vegetation map is not always helpful; an overlay may be a more appropriate method of illustrating the relationship between features.
The scale of the map will be largely determined by the degree of detail which is being presented.
Map makers have available a variety of colours (shades and saturation) and combinations of different colours in lines, hatching and symbols with which to illustrate the features of different communities and the relationships between communities. Symbols which may be either side elevation or plan, can be printed in black, either to enhance the information conveyed by the colour or to provide additional information. Numbers can be used to subdivide a colour into separate but closely related units, or they can be introduced to facilitate reference to the legend.
Map makers must choose colours logically and should remember that some users have difficulty in distinguishing between similar shades; many users will be deterred by very complex combinations of colours such as stripes, dots or symbols. (Printed symbols are probably more easily recognised than colour symbols.) As far as possible maps should be aesthetically pleasing.
The amount of information which is included in the legend will depend on the purpose for which the map is intended; elaborate legends are improved by grouping units together under a small number of descriptive headings. Descriptive vernacular terms should always be explained.
Many organisations are currently producing photomaps using both aircraft and satellite photography. Features are enhanced and photographs may be rectified for the production of these visually attractive maps; as thematic maps they will require evaluation.
Even in a note as brief as this it is necessary to acknowledge the immense contribution made by Professor H. Gaussen to the mapping of vegetation, and also the work of Professor A.W. Küchler.