A new basis for the relationship between the (vertical) earthview E of cloud amount and the (whole dome) skycover S of cloud amount has been sought. Over 4500 all-sky camera photographs, representing a considerable range of seasonal and climatological conditions, have been analysed to give rise to a database from which predictive relationships have been established. Cubic functions are the most soundly based both physically and empirically. We find 5=0.647 +2.192E−0.461E2 + 0.037E3 and E=−0.001 + 0.082S + 0.269S2−0.019S3 for the prediction of skycover from earthview and earthview from skycover respectively. If earthview is required from skycover observations then E ≈ S could be used with little additional error. Hence conventional surface observations of skycover could be compared directly with earthview values derived from satellite sensors.