Chapter 1: Context and Concepts

  1. Photographs were not very useful because they had to be enlarged to an impractical size to be legible.

  2. From the Latin c(h)art(a) and Greek graph(os), something drawn or written, hence "chart drawing."

  3. India ink is a mixture of lampblack and glue.

  4. This grid is also known as a graticule, a term meaning the spherical pattern of meridians (north-south longitude lines) and parallels (east-west latitude lines). See Campbell, 1993, p. 23.

  5. Mercator's projection, developed by and named for Gerhardus Mercator (1512-1594), a Flemish cartographer, is useful for navigation because a straight line on the map represents a true direction on the Earth's surface.

  6. Equal-area projections, as the name implies, accurately represent area, but not shape. This type of projection shows area distributions such as vegetation, in which the area shown is critical.

  7. Conformal projections retain correct shapes. An added advantage is that, if shape is retained, so is direction.

  8. Transverse Mercator has the projection cylinder fitted horizontally—i.e., east-west, rather than tangentially to the Equator or north-south.

  9. Latitude is relatively easy to determine with reference to "fixed" objects such as the North Star or the Sun. Longitude, as noted earlier, poses greater difficulties. It is known that the 360 degrees of longitude divided into the 24 hours of the day means that each hour is equivalent to 15 degrees of longitude. Thus, if the time at a known point could be maintained on a ship at sea, longitude could be calculated based on the time difference as established locally from the occurrence of the noon Sun. The problem, until John Harrison's invention of the reliable marine chronometer in 1761, was that no clock was able to retain its accuracy under the difficult conditions of a sea voyage. The extraordinary saga of Harrison's success is found in Sobel (1995). (I learned more than I cared to about this problem on a trip on a 30-foot sailboat from Honolulu, Hawaii, to Santa Barbara, California, when the crew forgot to set the chronometer on leaving Honolulu. The crew always knew their approximate latitude by using a sextant but never knew their longitude. Fortunately, they kept moving east and eventually bumped into North America.)

  10. In case inquiring minds want to know, 1 nautical mile, or "knot," is equivalent to 1 minute of latitude, or 1,852 meters (6,076.12 feet). One nautical mile is also equivalent to 1.1507 statute miles (Dent, 1990, p. 40).

  11. This happens because a GIS will try to put both locations on the same map in the originally specified map units. This may result in the map changing to extremely small scale (see explanation of scale in this chapter) as the GIS tries to make State plane coordinate values into degrees of latitude/longitude, placing the new data far, far away. The GIS may try to show data for small areas in Brooklyn and what it reads as Afghanistan or Antarctica on the same map.

  12. The term orientation is derived from medieval T-in-O maps. The "O" was the world ocean; the "T" was formed by the Mediterranean Sea (vertical), the Don River (left top of the T), and the Nile River (right top of the T). Paradise in this style of map was typically at the top, in the east. Hence the verb to "orient" a map came to mean adjusting it to its proper direction in relationship to the Earth. Today, however, we orient a map so that north is at the top, which is something of a misnomer (Campbell, 1993, pp. 246-247).

  13. From the Greek choros for place and plethos for fullness or crowding, hence "area crowd."

  14. Isolines based on continuous data, such as temperature or topography, are referred to as isometric lines. Actual measurements can be made to provide control points instead of averaging points over areas.

  15. The term "geography of opportunities" refers to the idea that the world offers abundant possibilities for crime that may be more complex than we realize at first glance, encompassing both qualitative and quantitative dimensions. For example, although rich neighborhoods may not offer more opportunities than poor neighborhoods for, say, property crime, each opportunity may offer the perpetrator higher value because the goods stolen may be worth more.
Chapter 1: Context and Concepts
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Mapping Crime: Principle and Practice, by Keith Harries, Ph.D., December 1999