Notes on microbarometer elevation determinations

Abstract

Barometers are frequently used to provide elevation control data for gravity surveys. Provision of reliable elevations by this means is not straightforward and depends on an appreciation of physical reduction factors, such as temperature or elevation itself, field technique and selective rejection of some observations. Data redundancy is essential. The theoretical and practical issues which affect interpretation of barometric data are briefly reviewed. Most errors can be traced to instrumental variability, observer inconsistency, inadequate controls or atmospheric abnormalities. An elevation accuracy of 1?1.5 m is possible given care in survey design and practice. Barometric elevation determinations in variable terrain must be based on careful, multiple and controlled observations. Pressure distortions within the atmosphere or around topographic features may invalidate many field techniques including those using base barometers. Considerable manual involvement is advised throughout the reduction process and unfortunately no simple universal sequence can be recommended. Local conditions must be uniquely assessed.