NE2001. II. Using Radio Propagation Data to Construct a Model for the Galactic Distribution of Free Electrons

In Paper I we present a new model for the Galactic distribution of free electrons. In this paper we describe the input data and methodology for determining the structure and parameters of the model. Tables of the input data are provided and several figures are used to demonstrate why particular Galactic structures are needed. We identify lines of sight on which discrete regions either enhance or diminish the dispersion or the scattering. Most do not coincide with known \ion{H}{2} regions or supershells, most likely because the enhancements correspond to column densities smaller than detection thresholds for the emission measure in recombination-line surveys.