5.1. Introduction

Quality control methods should be employed in the production of reported, adjusted and definitive data. Total field intensity values that are recorded using a proton precession magnetometer are an excellent tool for monitoring the measurement process that produces component values. The total field values may also be used to estimate the maximum likely range of error for component values. Baseline values are used to adjust component values for long-period, non-random error. A baseline adoption process may be used that provides confidence limits for component 1-minute and 1-second values. A tabular listing of annual baseline values and a description of baseline adjustments accompany the absolute data contained in the INTERMAGNET Reference data set (IRDS). A graphic display of baselines and differences in computed and recorded total field values are available to users.