High Precision Mapping of the Diffuse Low-Frequency Sky

One of the major science goals of international radio astronomy is to study the early universe through the detection of the redshifted 21 cm HI line from the epoch of reionisation (EoR). This spectral line is expected to fall in the 100 MHz to 200 MHz range. Due to the weak nature of the 21 cm signal, an important part in the detection of the EoR is removing contaminating foregrounds from our observations as they are three to five orders of magnitude brighter. In order to achieve this, sky maps spanning a wide range of frequencies and angular scales are required for calibration and foreground subtraction. Although sky maps with small angular scales are generally well represented, diffuse all-sky maps, especially on the southern hemisphere and in the expected EoR frequency range, are not. Mapping the diffuse sky, however, is a complex endeavour and tradeoffs are often made between maintaining wide field accuracy and computationally efficiency. In this thesis, the concept of all-sky imaging with exact wide-field characteristics is further investigated. The primary focus is put on spherical harmonic transit interferometry, with emphasis on completeness in angular scale as well as the ability to accurately map the intensity of sky.