Design to improve the productivity and execution of gravity surveys

The National Oceanic and Atmospheric Administration (NOAA) is responsible for conducting gravity surveys which are used to measure the variations in the pull of gravity of the earth's surface. Gravity surveys are vital for the country's safety (e.g. creation of flood plain maps and evacuation routes) and the economy (e.g. used for detecting petroleum and natural gas). The current set of gravity measurements known as the North American Vertical Datum of 1988 (NAVD 88') are outdated and lack complete coverage of the United States and its territories (e.g. Alaska has minimal data coverage). To improve accuracy, NOAA has begun a new survey, named GRAV-D, to combine existing ground (high definition) and satellite data (low definition) along with new aerial data (taken from aircraft) to establish the new datum. There is a complex logistical process in conducting the aerial surveys that are subject to large uncertainties due to weather, vehicle and personnel availability, and equipment failures. This paper describes the design of a logistics process to reduce the variation in the standard survey block from 24.59 to 15.11 days/survey. This is required to meet a Congressional mandate stipulating that the survey be completed by 2022. Analysis of factors affecting the completion of block surveys indicates high variability in aircraft maintenance, equipment repair, and weather related delays. Analysis using a decisionsupport tool designed to assist planners in managing the process by identifying elements that contribute to schedule risk, and advising mitigating strategies, indicates improved contingency planning through: (i) additional spares, (ii) additional support personnel, (iii) weather forecasting, and (iv) improved coordination among contractors would significantly reduce delays in the execution of the plans.