The work presented in this thesis was motivated by several considerations, the first being a practical one. By 1992, when this work was initiated, the Southern Hemisphere VLBI Experiment (SHEVE) array had been developed to the point at which it was operating at frequencies between 2.3 and 8.4 GHz, with up to seven stations participating in imaging experiments, and with maximum baseline lengths of close to 10,000 km yielding angular resolutions for imaging of less than one milliarcsecond (mas). The fact that the array was operating reliably and regularly meant that, for the first time, systematic, high quality imaging studies of compact radio sources could be undertaken from the Southern Hemisphere. At this time several projects were initiated, including an imaging survey of peaked-spectrum radio sources [King 1994], a survey of gravitational lens candidates [Lovell 1996], and the work presented here.
The scientific motivation for the study of a sample of nearby, bright, and compact radio sources was two-fold. Firstly, defining samples of compact radio sources, observing a representative number of them, and attempting to elucidate their properties is a well demonstrated tool for understanding the compact radio source population (e.g. Pearson & Readhead 1988; Polatidis et al. 1995). By choosing to study the brightest, nearest compact radio sources in the Southern Hemisphere, a ``Whole-Sky'' sample of such sources can be assembled for the first time. Since only a handful of these sources are accessible from each hemisphere, Southern Hemisphere VLBI observations are a valuable addition to the Northern Hemisphere observations which have been available for some time.
Secondly, for the purposes of investigating the detailed behaviour of individual sources, or classes of sources, rather than the gross properties of the entire source population, multi epoch and multi frequency campaigns aimed at single targets are required. The ``Whole-Sky'' sample consists of the brightest, nearest compact radio sources, providing unprecedented opportunities for parsec (pc) and sub-pc-scale spatial resolution VLBI imaging campaigns. Furthermore, because the radio sources are nearby, their host galaxies are generally prominent and well studied at radio wavelengths at arcsecond resolution, as well as at optical wavelengths, and even extending to X-ray and gamma-ray wavelengths.
Therefore, some unique opportunities exist to investigate the relationships between the compact structure of radio sources and their environments, thereby obtaining a view of the processes taking place in radio loud active galactic nuclei (AGN) over many orders of magnitude in spatial scale.