Homography-based correction of positional errors in MRT survey

Abstract

The Mauritius Radio Telescope (MRT) images show systematics in the positional errors of sources when compared to source positions in the Molonglo Reference Catalogue (MRC). We have applied two-dimensional homography to correct positional errors in the image domain and avoid re-processing the visibility data. Positions of bright (above 15 σ) sources, common to MRT and MRC catalogues, are used to set up an over-determined system to solve for the 2-D homography matrix. After correction, the errors are found to be within 10% of the beamwidth for these bright sources and the systematics are eliminated from the images.