In this chapter, we discussed many of the core concepts that underlie GIS development, examined some of the more common GIS data formats, and got our hands dirty exploring US state data downloaded from the US Census Bureau web site.
We saw that locations are often, but not always, represented using coordinates, learned that calculating the distance between two points requires you to take into account the curvature of the Earth's surface, and discovered why you must always be aware of the units used by geospatial data.
We then learned about map projections, which represent the three-dimensional shape of the Earth's surface as a two-dimensional plane, and saw that there are three main classes of map projection: cylindrical, conic, and azimuthal. We discovered that datums are mathematical models of the Earth's shape, and learned that the three most common datums in use are called NAD 27, NAD 83, and WGS 84.
We next examined the concept of coordinate systems and saw that these are used...