Agriculture Reference
In-Depth Information
mapS Serve a variety of purpoSeS
The illustrations provided by Figures 6.4 and 6.5 serve to underline the
idea that maps are made for a purpose and will require a range of infor-
mation types and detail depending on the circumstance. Depending on
a map's purpose and the circumstance in which it is made, a prescribed
set of data references will make it significantly more useful in carry-
ing out an activity such as locating a specific point on the earth or for
way-finding. In the case of Figure 6.4, the critical information making
that map useful was the inclusion of pertinent landmarks and their rel-
ative positions and order. The quality and accuracy of drafting was not
important for the map in Figure 6.4 to be useful. Important information
to make Map C in Figure 6.5-C useful was the inclusion of scale, a known
horizontal reference system, topographic contours, and the shape of the
islands, to allow the treasure hunter to locate the buried treasure. The
accuracy of the outline of the island was not critically important, but a
fair approximation of the landform shapes made the map useful.
Translating what was just presented to the activity of site grading,
a set of conventional information is necessary in order to create a useful
site-grading plan. A plan is a map of sorts, as it is intended to represent a
set of spatial information in a two-dimensional format. The information
requirements for creating a site-grading plan are described in earlier
chapters. Also, a site-grading plan utilizes a set of drawing conventions,
as discussed in Chapter 4.
coordinate SyStemS
Latitude and Longitude: a Geographic coordinate System
A common system for locating points on the earth is called the geo-
graphic coordinate system. This system uses degrees of latitude and
longitude to describe a geographic location or feature on the earth's sur-
face. Latitude lines run parallel to the equator. Lines of latitude divide
the earth into 180 equal portions between the North and South Poles.
The equator is the reference or starting latitude line and is identified as
