Geography Reference
In-Depth Information
You are not likely to find all these features on a single map. If you have multiple maps, you certainly have
two major problems, and you probably have three.
First, just inspecting several maps for the right combination of factors is quite difficult. How would
you determine where to put the airport? You could pin the maps side by side on a wall and look at
them. “Here's a location with nice large, flat area on Map A.” “Whoops, no. Map B shows the soil
wouldn't support a runway.” Trying to look at several maps in a serial fashion is not easy.
❏
The maps you will be able to get will be different shapes, at different scales, using different
projections and different units, and will cover different areas.
❏
Maps get out-of-date. A U.S. Geological Survey topographic map covering part of Lexington,
Kentucky, was produced in 1965. It was updated in 1993. During that time interval, the city grew by
100,000 people. It takes a lot of time to produce a good map. Even as soon as a map is published, it is
out-of-date. Of course, part of this problem occurs because it is impractical to survey and record all
significant changes just as they occur. But another major problem is that once a map is printed, the
publisher cannot change it. If the accuracy of a map is critical, as with aeronautical maps, an updated
version can be reissued frequently. With GIS, changes can be made to maps as soon as information
about changes becomes available.
❏
On the other side of this coin is the considerable value that maps, as they have been made for the last
several decades, have for many sorts of activities:
Maps provide a visually intuitive reference to the features and activities of an area of interest. They
connect us with our environment with a level of directness and lack of ambiguity that one may not
get with the “black box” and small screen of the computer.
❏
Maps are easily portable. They don't weigh you down. They display information you can read
out of doors—something your laptop computer or tablet may not do. They don't need batteries or
charging; thus they don't expire in the field at inopportune times.
❏
Maps usually give you large display areas. Yes, you can zoom to great levels of detail and pan on
a computer screen or a tablet screen. But there are times when you need both a reasonable level of
detail and a large view. It's hard to beat six square feet of map in those instances.
❏
Many maps are basically honest. Those produced by the U.S. National Mapping Program adhere
to rigid standards. (Look at
http://nationalmap.gov/standards.
) Frankly, the ability to provide
users with measures of accuracy and quality control is something that all GIS programs fail at
because vendors haven't truly gotten to it yet. The move to associate metadata with GIS datasets
goes in the right direction, but when you combine GIS datasets, there is no hint as to how good the
resulting datasets are.
❏
Force for Change #2: The Need for Better Resource Allocation
and Environmental Protection Became Evident
Before the 1960s, it was the view that the source of things humans wanted, such as land, resources,
energy, air, and water, was independent of the sink where we put things we no longer wanted, such as
garbage, heat, sewage, and combustion products. (See Figure 2-1)
Search WWH ::
Custom Search