For mapmaking, and for environmental analysis, each of piece of data should be linked to a precise location on the earth. But finding the precise location of the billions of pieces of information EPA uses is not easy. Fortunately, new technologies have made precision and accuracy easier to achieve. The challenge of mapping locations accurately Knowing precisely where you are on the earth is not as straightforward as it may seem.
Many factors affect locational accuracy in mapping.
Distortions result from converting a spherical earth to a flat map, as mentioned in the discussion on map projections . The earth is not a perfect sphere, really somewhat pear shaped, making this even more difficult. Precise surveying and geodesy , the science of understanding the shape, form and measurement of the physical characteristics of the earth, have improved the precision to which base maps are compiled. And especially, the challenge of identifying each location precisely and uniquely. EPA uses data collected by a variety of groups for a variety of applications using a variety of techniques.