Solar differential rotation determined by tracing coronal bright points inSOHO-EIT images - I. Interactive and automatic methods of data reduction

Full-disc solar images obtained with the Extreme Ultraviolet Imaging Telesc ope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse solar differential rotation determined by tracing coronal bright points. Two different procedures were developed and compared: an interacti ve and an automatic method. The interactive method is based on the visual t racing of coronal bright points in consecutive images using computer progra ms written in the Interactive Data Language (IDL). The automatic method rel ies on the IDL procedure "Regions Of Interest (ROI) segmentation" which is used to detect and follow bright points in triplets of consecutive images. The test-results obtained applying both methods by different persons who pe rformed tracing are presented and compared. The advantages and disadvantage s of the two methods are discussed.