We investigated resonant light scattering properties of single wavelength-scale metallic or dielectric nanorods in the energy-momentum space. High-refractive-index silicon nanostructures supporting strong Mie resonances allow light manipulation beyond the optical diffraction limit. Based on dark-field microscopy and numerical modal analysis, we revealed that the waveguide dispersion of the silicon nanorod determines and controls the resonant scattering properties. We also demonstrated for the first time quantitative measurement of the differential far-field scattering cross-section of a single metal nanostructure over the full hemisphere. While conventional back-focal-plane imaging suffers from optical aberration/distortion and numerical aperture limit of the objective lens, goniometer-based direct solid angle scanning provides quantitative and flawless information of far-field scattering from nanostructures on the wavelength scale or less.