Maps and spatial information technologies (Geographical Information Systems) in health and environment decision-making
A map is primarily a means of display; it cannot predict the patterns of distribution or relationships between resources. In Figure 1, for example, the map does not infer a causal relationship, it merely points out that there are some spatial coincidences that are worth exploring, to see if a causal relationship exists. Likewise, to show how changes in one resource may impact distribution of another resource, the relationship must be known and put into the model creating the map.
Most maps, unless they use data that are recorded in real time or near-real time (see Figure 5), represent only a snapshot of the situation at a particular time in history. As the environment is extremely dynamic, and conditions (many of which impact on health) are constantly changing, maps can quickly become outdated. Updating maps can be expensive in terms of the time required to make the maps and the cost of the information inputs required. In cases where current information is required (for example, monitoring of pollution dispersal from accidents or leaks), obtaining spatial information may be difficult or costly.
The Centre for International Earth Science Information Network (CIESIN) has used satellite-derived data to compile an Ultraviolet Index (UVI) and animated the maps to show the year to date. This can be used to issue health warnings to residents and travellers on a daily basis.
Another limitation of spatially-referenced environmental information is that access is often limited. For example, data may be available for only a portion of the required area, or for the whole area but taken from two or more different sampling exercises which may have used different sampling methodologies, scales, or accuracy levels.
Connected to this are costs involved in generating maps, and in printing, disseminating, and updating them. This requires specialized hardware and software, trained personnel, and often expensive and time-consuming means of acquiring, checking, interpreting, and inputting information.
Furthermore, the technology is rapidly advancing, and thus new applications and training courses are required on an almost annual basis. It is difficult for any non-commercial enterprise to keep up with these costs, but those in developing countries are most affected. The obvious result is that there are frequently data gaps or inaccuracies.
Finally, not all people can readily relate to information in a two-dimensional spatial format, especially if the map is of an unfamiliar area or is presented in an unusual projection. Furthermore, different cultures place different importance or meaning on symbols and colours. For example, western cultures may use the colour red to symbolize danger or an area where conditions are bad, but in China this colour would symbolize luck or a favourable area.
In summary, maps are useful communication tools if they have been developed according to the best available information (about both the environmental conditions and the targeted users). However, they should be used together with – not in lieu of – other information, such as documents, discussions, and models.