The reanalysed December data was then compared with the Slough data to see if the reanalysis of the Chilton data had any significant effect on the comparison between the two sites. The following points emerged from this comparison.

**M3000(F2)**. The scatter of points is not significantly reduced, but the lower values from Chilton are increased slightly.**fmin**. The reanalysis of fmin values has resulted in a much better correlation and the resulting best fit line through the data. The scatter of points has not been significantly reduced however, and this remaining difference is probably an instrument effect.**foE**. The reanalysis of foE values has slightly improved the gradient. The correlation coefficient has not changed.**foEs**has an almost identical distribution of points than before. The Chilton sounder seeing denser layers than Slough on a large number of occasions. This is most likely an instrument effect.**foF1**. A few of the Chilton data points have been discarded after reanalysis, leaving only two points. Although no significant line can be fitted through these points, one of the remaining points is in good agreement!**foF2**The foF2 statistics are largely unchanged. The correlation, and offset values are slightly improved.**FxI**. The rescaled values are almost unchanged.**h'E**. The scatter of points is increased for the reanalysed data. This is in part due to the increased number of Chilton points that have been set to 90 km.**h'Es**. After reanalysis, this parameter is more clearly divided into two groups of points. Those whose h'Es values agree, and those whose Chilton values are anomalously low. This has resulted in the correlation between the two data sets increasing.**h'F**. The distribution of points has remained largely unchanged, although the correlation has dropped by two percent.**h'F2**. The addition of several higher common h'F2 points has resulted in a more well defined distribution of values. All the points lie below the expected line however.

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19/02/97 Chris Davis