Geography Reference
In-Depth Information
translates to only an eighth of an inch on one “2000-scale map,” where 1 inch corresponds to 2000 feet.
(The scale is 1:24000 - a standard scale for US topo maps.)
An eighth of an inch certainly does not supply enough space to show these features and the relationships
between them. If the symbols for these features are shown in their correct spatial locations, they will
appear on top of each other. What is the cartographer to do? Fudge! Widen the valley and exaggerate the
distances between the features, which means putting some of them in places where they, in fact, do not
exist. “Generalize” is a term that is used for this. The cartographer rightly deems it more important to
show the correct relationships among the features than to be precisely spatially accurate.
One can correctly argue that such adjustments should not be a part of a GIS database. The different uses,
at different scales, of GIS data suggest that everything placed in the database should be recorded as
accurately and precisely as reasonably possible. This means that if a map is made or data displayed at the
1:24000 scale from such a database, you would not be able to distinguish among the features. To see the
features in their proper relationships, you would need to zoom to a larger scale.
This incompatibility between the paper map and GIS will be exacerbated as more and more detail is
introduced into GIS databases. The incompatibility, along with the lack of GIS tools for good mapmaking
(a problem that is actually fast disappearing), is why many cartographers convert GIS maps into drawing
programs like Freehand and Illustrator. In any event, the virtual map or the Web-based map, will not
push the paper map into antiquity, but the trend will be in that direction. After all, what is usually
desired is to have spatial data and analysis tools that will create products for decision makers.
Products of a Geographic Information System
Let's shift focus from learning GIS to thinking about the desired end results. By this I mean the decisions
taken by human beings to change, navigate, or protect the environment.
C. P. Snow wrote, “To be any good, in his youth, at least, a scientist has to think of one thing deeply
and obsessively for a long time. An administrator has to think of a great many things, widely, in their
interconnections, for a short time.” 2 It is to the attention of these administrators that products of a GIS are
mostly directed. You, as a producer of information, need to be mindful of limits on their time.
Overall Requirements for Utility
To be useful in decision making, products of a GIS must meet several criteria:
1. The decision makers must know it is available.
2. They must be able to understand it.
3. They must have some reason to believe that it is worth their time to determine how to use it.
4. Assistance to aid the decision makers' understanding of the product must be available.
5. The product must be available at the time it is needed.
6. It must be relevant to the area of concern.
2 Snow, C.P., 1961. Science and Government . London: Oxford University Press.
 
 
Search WWH ::




Custom Search