
%0 Journal Article
%A Green, Andy 
%T Correcting Drift Errors in HEM Data
%J ASEG Extended Abstracts
%D 2003/08/01
%V 2003
%N 2
%P 1-1
%K 
%R https://doi.org/10.1071/ASEG2003AB058
%U https://www.publish.csiro.au/paper/ASEG2003AB058 
%X Much HEM survey data suffers from low (spatial) frequency along-line variability in amplitude caused by slow changes in the system geometry and electronic drift. Even though the system is periodically taken up to a sufficient altitude to re-zero the primary field correction, the errors are not totally removed. This paper describes a procedure to reduce the effect of these errors. Each flight line is corrected by subtracting a slowly varying function of time that has been chosen so that the between-line differences over the whole survey area are minimized. The parameters of the correction functions are estimated using weighted, damped least squares. The procedure produces a marked improvement in the quality of the images of low frequency, in-phase channels that have been corrupted by drift noise. 
